NASA's Voyager Mission: Remastered [4K]

ah it was the spring of 1965 on the eve of the first manned missions in the long developed project gemini that a supervisor at jpl joe cutting head of the advanced projects group approached his team to conduct an in-depth study of potentially useful outer planet mission profiles and launch opportunities in the near future with the conclusion of the international geophysical year almost a decade earlier the united states had gone head-to-head with the soviet union in a robotic race to the moon and had roundly lost the allure of the moon and dominance in space proved irresistible and had become the target of the much more popular much better funded and much more politically relevant manned program unmanned exploration through the 1960s progressed in a subservient role ranger and lunar orbiter were merely scouting trips reconnaissance for later apollo the possibility however of flights to other planets had captivated and held the interest of many in a way like nothing else except the apollo missions themselves that goal became the next logical evolution of the unmanned exploration programs in retrospect there tends to be an inflation of the perceived scientific focus of the unmanned programs viewed in contrast to the political and technological superiority goals of the manned flights this argument has often been made to downplay the scientific achievements of manned missions in favor of those of robotic missions which are described as being more scientifically pure in design and intent but for all the genuine importance of magnetospheric physics and gravimetric studies it was quite simply the promise of photographs of the planets that appealed to a broad swath of the american public and lit the fire that would push unmanned exploration forward through the golden age of space flight it was in this context that the united states and the soviet union opened a new chapter in their competition above the atmosphere a race to the planets this was also the first race in which the soviet union had experienced a loss with the american mission of mariner 2 reaching venus in december of 1962. by 1965 when gary flandreau and his colleagues part of joe cutting's team were given the task of studying near future opportunities for missions to the outer planets it seemed intuitive it was the next obvious step in a space race with snowballing momentum each and every year budgets and ambitions climbed it was unlikely however in 1965 that sufficient rocket power would be allocated to the unmanned program to facilitate outer planet exploration which was to put it a certain way a whole new ball game consider an imaginary solar system several planets orbiting around a centrally located star the closer planets more powerfully affected by the star's gravity orbit faster more distant planets not only have a much greater circumference to travel in their orbit but because of gravity or in this case the lack thereof they also orbit more slowly for interplanetary travel minimizing fuel consumption is the name of the game gravity and velocity are the dominant factors in trajectory planning if you're trying to get from the innermost planet to the outermost planet you wait allowing the planets to orbit the sun until they reach a certain magical position relative to each other launch at this moment called a home and window and you can speed up boosting away from your home planet and coasting outward aiming for a point in space ahead of your target and hopefully with enough precision and a little luck getting close enough to fall into its gravity well transfer windows between the earth and any of the other planets in our solar system happen essentially all the time at least once a relative year they aren't incredibly special but flandreau's supervisor joe cutting was studying the application of an intermediate planetary gravity assist in mission profiles to mercury via venus think of it as a double transfer window first you take advantage of a window from earth to venus and by the time you reach venus another transfer window will have opened between venus and mercury allowing you to use venus's gravity to bend your trajectory in just the right direction to send you there no major engine burn is required since you're already coming in at escape velocity with too much energy for venus's gravity to capture you on its own this work would lead to the highly successful mariner 10 mission in 1973. the idea behind a gravity assist was fairly straightforward to minimize the amount of rocket needed to push an exploration payload such as a robotic probe if the gravity of a halfway planet could be utilized in some respect to bend that payload's outbound trajectory towards the final target planet it would save precious weight and fuel in 1965 such a strategy would be crucial for success given nasa's limited lifting capability this trajectory shaping method might just be applicable in outer planet exploration and early on flandro followed this road [Music] much of the theoretical work had already been done by people like german rocket engineer craft erika and by astronomers and mathematicians of the copernican age such as urban le verrier who knew about the importance of planetary gravity fields in perturbing the orbital paths of comets graphing of the heliocentric positions of the planets and analyzing their historical trends allowed flandrow to make accurate predictions of planetary positions in the future his work led him to realize that there would be a quadruple convergence just before the 1980s a once in every 176-year occurrence where all four gas giants would be on the same side of the sun and in the proper relative position for multiple outbound gravity assists one probe launched towards jupiter sometime in the mid 1970s with the utmost accuracy and precision the likes of which had never been attempted before and would not be necessary again could in theory swing from jupiter to saturn to uranus to neptune all without a major requirement of fuel after the initial boost out of earth orbit the genesis of this realization was spawned on the third floor of building 180 at jpl in the summer of 1965. in an incredible coincidence the convergence wouldn't happen for just over a decade leaving enough time to design market hopefully fund and build a spacecraft assuming of course the mission concept was approved the four planet mission profile came to be called the grand tour and it began generating buzz when in 1966 flandero publicly published his findings he outlined several possible profiles there were two major constraints the first of course was delta v the necessary speed to attain this complex trajectory this would be incumbent on both the weight and complexity of the probe itself as well as the relative power of its launch vehicle the key here is to use free energy that you can it's not using rockets now we're using some free energy which i will explain jupiter is moving along and it's pulling us with its gravity field we sometimes call that gravity assist adds a tremendous boost of energy but that's equivalent to about four saturn v rockets waiting for you out there if you could hook those up you can really get a tremendous boost in speed heads over there to uh saturn and you're getting a huge boost and you can get them to uranus really quickly and then on to neptune and then we're on the way out of the solar system that's where we go interstellar at that point but the interesting thing here and by the way uh here i am doing these things i say how could we ever sell this but the key to selling it is to notice that some important event happens within four year time spans the other constraint was time this would be a mission like no other one that would last not just years but well over a decade or possibly more gary flandro still a student would leave jpl long before his vision would be implemented dr james van allen the same van allen whose instruments on america's first satellite explorer 1 had discovered the radiation belts around earth that bear his name became a vocal advocate for outer solar system exploration during a period of shifting priorities and budget cuts for nasa as support for apollo waned the promise of bigger and better unmanned missions filling the exploration role at a fraction of the cost now seemed highly appealing to the nixon administration which wanted to distance itself and establish a new direction away from the kennedy and johnson vision of american space flight the scope of the grand tour project wildly fluctuated during this time at one point jpl considered four separate but identical missions to capitalize on the incredibly rare opportunity but over at nasa these proposals soon found themselves competing with the newly inaugurated space shuttle project for funding nasa was slow to embrace grand tour it already had its own outer planet exploration missions developed by a completely separate team pioneer reaching out to other planets once thought to be inaccessible now within reach it flies to jupiter takes pictures then soars off through and beyond the solar system beyond our comprehension of space and time pioneer 10 and pioneer 11 both of which would fly by jupiter utilizing the gravity assist concept pioneer 11 would go on to fly by saturn apart from a single on-board scientific instrument jpl was out of the loop the novelty of the grand tour concept had worn off its very goals undercut by a different american robotic exploration team [Music] 1971 the four mission four planet concept was officially rejected in 1972 nasa instead approved something else entirely called mariner jupiter saturn it was to be a series of two identical flights both of which would fly past the fifth and sixth planets little more than a rehash of pioneer 10 and 11. but in nasa's thinking the pioneer probes both of which will encounter jupiter and one of which will continue on to saturn are small and fairly primitive they are merely reconnaissance missions leaving much to be desired as far as in-depth study is concerned that is the official stated purpose of mariner jupiter saturn jpl's probes would be more than three times heavier and much more sophisticated nasa wants to use these probes to revisit these two planets and study them with a much more complex suite of instrumentation [Music] the real kicker is that these probes would launch in the late 1970s during the four planet alignment yet nasa had no plan to take advantage of it everything we now do every advance in knowledge we now make contributes to that and just because i can't see it doesn't mean it isn't there and if we refuse to take those steps because we don't see what the future holds all we're making certain of is that the future won't exist and that we will stagnate forever and this is a dreadful thought and i am very tired when people ask me what's the good of it because the proper answer is you may never know but your grandchildren will despite the limited official aims of these new flights which were to utilize gary flanders late 70s launch windows a culture of stubborn persistence developed at jpl despite a limited budget engineers had every intention of designing spacecraft that would remain functioning well after the saturn encounter even if nasa had no public intention of operating beyond saturnian space there was a hidden unstated agreement between the engineers and the scientists during the design and building phase of these flights those on the ground at jpl quietly acknowledged the possibility of pursuing a further encounter with uranus and possibly after that even neptune should the spacecraft remain healthy by 1972 they had been sort of downsized to mjs 77 which is mariner jupiter saturn uh four-year mission uh just to those two giant planets and their moons and rings that uh fortunately was to be launched in 1977 however so that if they continue to work they could go on to uranus and then finally neptune completing the grand tour of the outer planets in 12 years rather than 30 years although it had been officially rejected grand tour was slowly coming back from the dead not by any top-down managerial decisions but instead by an organic bottom-up quasi-conspiracy between those who truly believed in the importance of such a flight slowly but surely over the years secondary objectives were quietly tacked on piece by piece regardless of which objectives or instruments the scientific community recommended for mariner jupiter saturn jpl insists early on on including television cameras photography was to be a central aspect of these flights and indeed a slightly longer trajectory was chosen for the explicit purpose of providing the ideal lighting conditions for photography during the jupiter and saturn encounters the design and experience from prior mariner missions used wherever possible and supplanted with subsystems designed for the viking orbiters they requested the atomic energy commission upgrade the plutonium rtgs so that they would last more than 10 years they developed a reprogrammable onboard computer something that would be critical to the prospect of an open-ended long-term mission in space pioneer 10 traverses the asteroid belt in late 1972 and arrives at jupiter in november of 1973. it passes jupiter at a distance of 132 000 kilometers some 71 000 nautical miles and becomes the first man-made object to encounter the gas giant and beams back the first ever photos of jupiter in detail the levels of radiation at jupiter were much stronger than expected by a factor of nearly a thousand the product of a massive magnetic field pioneer 11 would itself encounter jupiter a year later and then begin a long lonely journey towards saturn which it wouldn't encounter until 1979 well after the launch of the two jpl probes the pioneer encounter at jupiter had a profound effect on the development phase of mariner jupiter saturn because of the intense radiation encountered far stronger than anyone had expected certain scientific experiments initially selected were dropped and others were added ultimately there would be 11 chosen areas of investigation imaging radio science ir and uv spectroscopy magnetometry charged particles cosmic rays photopolarimetry which is to say the study of the intensity and polarization of reflected light such as from clouds in a planet's atmosphere planetary radio astronomy plasma and particulate matter each field of scientific inquiry has its own principal investigator but the heads of the imaging and radio science groups were designated overall team leaders the position of lead project scientist was given to ed stone a magnetospheric physicist from caltech who had been working on grand tour since 1970. stone is keenly aware of the public's impact on space exploration and vice versa and firmly believes in the importance of communication and public relations he decides early on that scientific findings will be crystallized summarized and shared with the public as soon as they are made available the basic structure and beating heart of the spacecraft is called the bus it is a large ten-sided box on top of this box rests the high gain antenna on what is called the z-axis the spacecraft is designed to roll about this axis via the firing of rcs thrusters attached to the bus each of the 10 sides contains a small bay that houses various electronic assemblies attached to the bus are several external components of varying purpose the science boom anchors three instruments dedicated to studying particles in space the cosmic ray instrument the plasma science instrument and the low energy charged particle detector at the end of the science boom is a movable platform that houses the optical sensing instruments including the incredibly important image science subsystem the iss consists of two black and white television cameras a modified version of the slow scan vidicon camera designs used in earlier mariner flights also mounted on the platform is the photopolarimeter a small telescope with polarizing filters to study atmospheric particles searching for evidence of lightning and auroras another instrument the infrared interferometer spectrometer and radiometer or iris generates temperature profiles of the outer planets studies what types of elements are present in their atmospheres and measures the amount of sunlight they reflect there is also a specialized ultraviolet spectrometer [Music] on the opposite side of the spacecraft is a 43 foot fiberglass boom nicknamed the astro mast that houses the magnetometers its length ensures that the spacecraft's onboard electronics don't interfere with magnetic readings a smaller boom located below holds the radioactive power source the rtg [Music] there are three of them mounted inline each is made of a plutonium-238 fuel source consisting of small pellets inside that release alpha particles these particles which are essentially naked helium nuclei bombard the inner surface of their containers this heat is converted into electricity by an array of thermocouples which is then used to power the spacecraft and its systems collectively they provide 470 watts of power at the beginning of the mission over the course of time the deterioration of wires thermal contacts and the radioactive fuel itself will lead to a slow decrease of output the high gain antenna is capable of both x and s band downlink data could be stored onboard for later transmission through the use of an onboard digital tape recorder the belt driven recorder uses a 328 meter long reel of 12 and a half millimeter wide magnetic tape recording data onto eight separate tracks it could record at a high bit rate of 115.2 kilobits per second and a low bid rate of 7.2 there is conflicting information as to how much data the dtr could actually hold and this value would decrease over time due to tape errors and hardware aging at launch it is believed the tape recording system could hold 536 million bits of information approximately 67 megabytes the equivalent of 100 full resolution photos two whip antennas extending out next to the rtg boom like a pair of bunny ears are the shared planetary radio astronomy and plasma wave subsystem antennas by this point the probes are so much more advanced in design and capability than their mariner ancestors that nasa organizes a competition to choose a new unique name on march 4th 1977 voyager was approved on august 4th 1977 at 12 pm nasa releases the official press kit for the voyager missions they are to launch aboard a titan 3e rocket also called the titan centaur this massive launch vehicle with a cryogenic upper stage is a far cry from the meagre titan twos that launched the gemini capsules into orbit lifting some 15 and a half thousand kilograms to low earth orbit some 34 000 pounds this type of rocket had launched the viking mars landers in 1975. in the press kit nasa finally acknowledges that a possible tertiary objective for the voyager 2 spacecraft will be to fly by uranus to this end voyager 2 would actually launch first at the end of august if lucky enough to obtain the maximum possible performance of the titan centaur it would just barely catch the old grand tour window discovered by gary flandro assuming it remained healthy an encounter with uranus after the saturn flyby would be a possibility voyager 1 would launch two weeks later on a much more fuel efficient and shorter route to jupiter it would actually arrive at jupiter four months ahead of voyager 2 despite launching later i think i was the last person to physically touch the spacecraft um right during the last step of encapsulation of the spacecraft we were worried about uh our fragile windows on our instrument so i was allowed to crawl up in there climb up in there and inspect them and part of the inspection process was to make sure that the little windows were tight on the on the telescopes so i gave each one a little twist the two voyagers would arrive at saturn nine months apart if voyager 1 failed to achieve its saturn objectives for any reason voyager 2 could be retargeted to achieve them at the expense of any subsequent uranus encounter it was a compromise voyager 2 would serve as a backup to cover voyager 1's jupiter and saturn objectives should however voyager 1 be successful in all aspects voyager 2 would have the option of a less valuable saturn flyby enabling it to visit uranus uranus is mentioned 19 times in the voyager press kit neptune is not mentioned once but for those in the know neptune is right where it would need to be should the decision come years down the line to continue voyager 2's planetary journey officially however there is no acknowledgment of anything that smacks of the original grand tour idea [Music] in all there were actually three voyager spacecraft built and given serial numbers but only two were ever planned to be launched the third was a quarter of a spacecraft at best to be used as a backup for parts in the event of any unsolvable pre-launch systems failures and less than a month before launch failures in two of the three on-board computers of the voyager 2 spacecraft result in an ad hoc switch the spacecraft that would have launched as voyager 1 is instead bumped up to the earlier slot and will instead fly as voyager 2. this will give nasa and jpl approximately two weeks to fix the broken computers if the reversed launch order wasn't already confusing enough let history record that the physical spacecraft themselves were switched at the last minute to facilitate repairs nasa has to swap the rtgs as well whichever probe launches as voyager 2 must reserve the option to continue its mission after saturn therefore one of the two sets of rtgs are for lack of a better term overclocked this will enable a longer guaranteed electrical output life cups and balls routine complete the mission is finally given the go for an on-time launch two years to the day after the launch of the viking mission to mars at 10 29 and 45 seconds am eastern daylight time the titan centaur's two massive solid rocket boosters are lit and there's no stopping them [Music] the program is in on time vehicle response was normally producing 1.2 very very small attitude disturbances the entire rocket spacecraft and fuel weigh a combined 1.4 million pounds just over 635 000 kilograms the two solid rocket boosters which burn alone for the first phase of powered flight comprising what is known as stage zero output nearly double this in thrust the guidance data coming back shows that we're right on the money for 117 seconds they spit fire the combustion products of a nasty mix of powdered aluminum fuel an ammonium perchlorate oxidizer bound together in a polymer known as p-band ten seconds prior to solid motor jettison the two lr-87 liquid engines of the core stage known as stage one are jump started in mid-air thanks to their use of a small solid rocket motor start cartridge shut down of the solid rocket motors the boosters from the titans four minutes and 20 seconds after launch staging occurs the lr91 single engine ignites and continues carrying the spacecraft higher faster and farther towards orbit eight minutes after launch just prior to entering orbit the lr91 runs out of fuel this is planned because the third stage is the real pusher the centaur high energy upper stage not visible during launch as it is enclosed within the fairing along with the payload is different from the two hypergolic liquid rocket stages that proceeded in that it feeds two rl10 cryogenic hydrolox engines like the old atlas rockets of the mercury program the centaur is a balloon tank its structural integrity is derived from the internal pressure of its fuels its walls are extremely thin and this combined with its incredibly efficient hydrogen fuel gives it an excellent energy to weight ratio like the s4b stage of the saturn v the centaur upper stage burns twice first to place itself and the voyager spacecraft into earth orbit and then 42 minutes later just half of one orbit of the earth it fires again this time it fires much longer imparting such incredible speed that not even earth's gravity can hold it back voyager 2 is on its way but the job isn't done just yet one hour after launch approximately 12 minutes after the conclusion of the second centaur burn the voyager spacecraft separates from the upper stage it's still got more speed to attain attached to the bottom of voyager is what is known as a kick motor officially called the propulsion unit this represents the last hard punch a voyager's outbound trajectory because it's a solid stage it can't be shut down or throttled it imparts a guaranteed velocity increase of 2000 meters per second or 4 500 miles per hour to ensure that voyager isn't going to overspeed the centaur is cut off deliberately early by the time the propulsion unit delivers its final boost it's throwing voyager right down the pipe a perfect insertion four externally mounted reaction control system pods provide attitude control during the chaotic 43 second final kick these siphon fuel from the main hydrazine tank located within the voyager bus when the star 37e solid motor finally separates having delivered on its mission it takes these rcs pods with it voyager itself has an array of 16 smaller hydrazine maneuvering thrusters these are primarily meant for attitude control and tiny mid-course corrections voyager's ability to change its own trajectory once released from its propulsion unit is now severely limited for all intents and purposes isaac newton is now in the driver's seat each voyager probe carries 105 kilograms or 231 pounds of hydrazine fuel for its reaction control system thrusters pressurized with inert helium gas at 420 psi [Music] two weeks elapse as voyager 2 begins its long coast towards jupiter voyager 1's flight data computer is successfully repaired and reinstalled its guidance computer however cannot be repaired it is instead replaced by the one from the third backup voyager spacecraft which was simply a proof test model and not originally meant to fly on september 5th 1977 voyager 1 joins its sibling beginning its journey towards jupiter voyager 1's boost phase was a close one the lr91 stage of the titan iii burned for a shorter period than it was supposed to meaning the liquid hydrogen centaur stage had to shoulder a bigger share of the burden 1200 more pounds of precious hydrolox fuel was consumed than planned it was a nail biter at the moment of the second centaur cutoff it was estimated that the stage was perhaps as close as 3.4 seconds away from total propellant exhaustion had the same failure occurred on voyager 2 because of its more fuel demanding flight profile the centaur would have run out of propellant before the probe had reached the proper trajectory and the solid rocket motor would have been unable to make up the difference somehow by the skin of their teeth jpl and nasa had squeaked by disaster voyager 1 had made it unmanned voyager spacecraft are on route to jupiter now the first voyager will reach the planet in march 1979 followed by the second spacecraft four months later then on to saturn at the time of closest encounter on november 12 1980 voyager 1 will have traveled 1.4 billion miles through space [Music] the voyager spacecraft each carry an optical guidance system that allows them to automatically determine their attitude in space it's important to know where you're pointed a sun sensor mounted in the high gain antenna allows the probe to point itself towards the sun thus aligning the dish with the inner solar system and therefore earth the body of the spacecraft then rolls until two star trackers working in a tandem binocular fashion are able to lock on to a known star based on its unique luminosity the star intended and most often used for this purpose is canopus one of the brightest stars in the celestial sphere the celestial navigation instruments feed data into the guidance computer aboard voyager there are in all three computer systems aboard this spacecraft the guidance computer is called high pace or hybrid programmable attitude control electronics it contains two redundant plated wire memory banks half of each contain fixed memory and the other half reprogrammable from the ground high pace monitors and controls the sun sensors star trackers the movable scanned platform on the science boom as well as a small inertial guidance unit for short periods of time should voyager need to break its optical sun celestial attitude lock a three-axis gyro can measure the drift away from the optic lock point allowing it to effectively memorize where it's looking this can be used during periods of scientific observation or instrument calibration the data those science instruments obtain will be routed through the second on-board computer known as the fds or flight data system this computer controls the science instruments themselves and formats all data for transmission to earth since voyager will be so far away from earth during its planetary encounters the bulk of its motion where to point its cameras and instruments when to take readings and when to transmit will be loaded onto its computers via ground transmission beforehand then like a player piano it will dutifully carry out these instructions without hesitation or greater awareness it is incumbent therefore on the voyager ground team to ensure that the dance they force voyager to do is proper one small error in the sequence and they may forever miss their chance to capture a yet to be discovered moon or snap an image of a fleeting cloud formation because these probes will be flying by the planets they are intended to study at breakneck speeds the time they have to collect meaningful data is measured not in days but in mere hours there and gone in the blink of an eye there is so much at stake the flight data system and the guidance computer are both controlled by a set of master computers called the computer command subsystem or ccs these computers essentially the same build as the high pace guidance computer nonetheless perform a completely separate function they store and issue the master command of spacecraft sequences whether that be an attitude maneuver or a series of timed commands to the science instruments if the guidance and data computers are the instruments in this orchestra then the ccs is the conductor command signals sent from the ground are transmitted through the deep space network system of massive radio telescopes at a rate of 16 bits per second to the spacecraft there is some minor concern that the science boom aboard voyager 2 is not latched as the proper confirmation signal was never sent however there is no indication at this point that the boom is loose or in motion just 22 days after launch voyager 1 is 21 million kilometers from the earth on september 16 1977 it calibrates its camera system by taking an image of the earth and moon both in a single frame it will be the last time voyager 1 images the earth as anything more than a pale blue dot [Music] through the end of 1977 both voyagers perform several small mid-course pulses with their hydrazine thrusters called tcm's or trajectory correction maneuvers these are to null out small errors and ensure optimal placement before reaching the critical jupiter encounter minor issues that are common to all space flights develop and are solved during the outbound coast a slight propellant deficit a bit failure in one of the ccs computers sticky motors and the decision to roll voyager 2 180 degrees to lock onto the star deneb instead of canopus to minimize solar radiation pressure things seem to be proceeding normally it had been planned to observe a near-earth comet kohler but this was cancelled there was disagreement amongst the image science subsystem team on whether or not it was prudent to work the imaging system so hard during this early cruise phase of the flight and also whether or not the brightness of the comet might damage the optics the spacecraft passes the orbit of mars in mid-november 1978. and voyager 1 finally overtakes voyager 2 on december 15th now finally worthy of its number both spacecraft continue to make leisurely observations of the celestial sphere and our sun primarily for instrument calibration purposes though some scientific data is being obtained during this portion of the mission small systems failures continue to pop up and continue to be resolved a frozen scan platform a stuck filter wheel on the photo polarimeter a decrease in sensitivity in the plasma experiment the vicious environment of space takes a constantly growing toll but then a major issue develops in voyager 2. the primary radio receiver experiences an unknown failure which causes excessive current blowing its fuses for an entire week all contact with voyager 2 is lost a timer in the command computer automatically switches to the redundant backup receiver after not receiving any commands for seven days thankfully communication with voyager 2 is reestablished it looks like the primary receiver is busted for good it will never work again the secondary receiver thanks to a faulty capacitor in its system is incapable of correcting for doppler shifts on the communications frequency not only is correcting for these shifts necessary for communication but measuring the shifts themselves was a way of determining velocity data from voyager 2 meaning alternate methods of positional navigation would have to be used for each subsequent transmission to voyager 2 engineers would have to calculate specific frequencies for outbound communication signals to correct for the earth's rotation yet another headache yet another burden if systems continued to fail at this rate the outlook for an extended mission was grim jpl's own mission bulletins from 1978 refer to the space probe as beleaguered scariest time was on voyager 2 when we lost one receiver and found that the backup receiver no longer could tune to the frequency we were sending so we had to learn how to send the right frequency so the spacecraft could fortunately we learned how to do that but that was a very scary period of several months while we sorted out what happened and what the workaround was but we've flown the entire mission now with uh this kind of tone def uh receiver and so that's fine there are many such things that happen on real missions uh and normally you don't hear about them because once they get fixed it's sort of old news so we're very lucky that there's been no catastrophic failure in either spacecraft yet but you know that's just the risk of space i mean things do happen that you can't fix just in case voyager 2's computer is loaded to the brim with commands that would provide for a bare minimum science encounter at both jupiter and saturn should radio uplink be lost for good only a year into their mission both voyagers have already consumed some 10 percent of their hydrazine maneuvering propellant and that was just during the cruise phase as the scan platform on the end of the science boom slews it imparts some rotational velocity to the bus the hydrazine thrusters can then be pulsed to counter this attempting to keep the spacecraft in as stable an orientation as possible nonetheless some amount of drifting chaos is unavoidable the narrow angle television camera one of two on voyager is magnified some 65 times relative to normal human eyesight its field of view spans just half of a single degree of the celestial sphere the scan platform itself has a margin of error of just one-fifth of this combine that with the chaotic motion and intermittent drifting of the bus significant pointing errors resulted in fact it was determined that a pointing error of up to one-third of the camera's field of view could be expected this would mean that the position of jupiter or any object for that matter in voyager's cameras would jump around significantly from frame to frame meaning significant post processing and stabilization would be necessary on the ground to create moving sequences the wide angle was only slightly better with an 8.7 times relative magnification its field of view spanning 3 degrees january 4th 1979 voyager 1 enters the observatory phase as it draws ever nearer to jupiter the probe begins firing on all cylinders doing daily system scans across its entire suite of scientific instruments on january 30th it begins a four day period of intensive jupiter imaging returning pictures in real time shuttering every 96 seconds for 100 hours capturing 10 jovian rotations [Music] [Music] this is what the unfiltered unprocessed raw images look like when played back at high speed all images returned from voyager are black and white at first how then are images like this possible how is color captured with a black and white camera the answer lies in the filter wheels like the photopolarimeter the television cameras have their own rotating wheel of translucent filters green blue orange ultraviolet and clear some of these filters have a scientific purpose designed to only let specific wavelengths of visible light through giving an indication of such things as the presence of sodium or methane in the atmospheres of planets but they can be used for a different purpose as well if you take three black and white images through green orange and violet filters and then dye these images their respective colors in a dark room on earth compositing them will produce synthesized color an approximation of the general true color distribution of the planet every color image from voyager is in fact a combination of at least three separate monochrome exposures and in some cases more than that this is essentially a much slower version of the apollo color television camera which automated this process in real time at a high rate of speed in a way post-processing has always been a part of voyager's story the immense distances it had to transmit data the relative imprecision of its pointing and even the errors in its own systems meant that voyager itself could only show us part of the picture we humans would have to do the work to piece together the entire puzzle and that work hasn't stopped since 1979 many many years later with the advent of personal computing people would come back to voyageur's data unlocking the secrets embedded in decades-old raster scans they would apply the powerful new tools of digital processing and photo enhancement to breathe new life into voyager's images what voyager really saw take for instance the story of dr mark showalter who in 1990 using 10-year-old voyager data discovered pan the 18th and innermost moon of saturn a shepherd moon orbiting within the rings themselves people like brian burns ian regan emily lochtawala bjorn johnson ted strick and dozens of others who have tirelessly stitched together massive panoramas and have created stabilized moving sequences incorporating color information from both voyager's own cameras and later missions their work makes voyager's data more accessible and enjoyable to us all and while the vast majority of them have nothing to do with nasa jpl or the official voyager mission their contributions are nonetheless an extremely visible part of the historical account of voyager occupying a beautiful halfway zone between art and science the contributions of these individuals and the digitization of these images showcased here and elsewhere has led to their rebirth [Music] by late february of 1979 voyager 1 was in jupiter's midst the largest single feature of jupiter is its magnetic field the strongest of any planet in the solar system extending nearly 7 million kilometers in the sun's direction and reaching the orbit of saturn in the other direction it is 20 000 times stronger than that of earth's generated by electrical currents in its outer core composed primarily of liquid metallic hydrogen hydrogen the lightest element in the universe is normally gaseous but when placed under conditions of extreme pressure it liquefies and can act as an electrical conductor this means that jupiter's magnetic field is the product of an entirely different mechanism than earth's which is produced primarily by a mixture of molten iron and nickel jupiter's magnetic field is blunted and shaped by the solar wind the supersonic stream of particles and radiation pressure given off from the sun this effect is common across all the magnetically active planets however as voyager 1 streams through the jovian system it encounters something wholly unexpected a massive ring of plasma around the planet composed of sulfur and oxygen ions the plasma torus in jupiter's equatorial plane co-rotates with the planet causing a deformation of the magnetic field into a flattened pancake-like disc electrons within the plasma generate a strong radio signature with short superimposed bursts making jupiter appear like a radio pulsar not counting its core jupiter is somewhere between 87 and 92 percent hydrogen another 8 to 12 percent helium and the rest is methane and ammonia with trace elements it is 11 times larger than the earth by diameter 1 321 times larger by volume and has 318 times more mass a gas giant it lacks a solid surface though it is believed to have a solid rocky core its appearance is a swirled mix of tans browns and oranges the outer atmosphere is subdivided into latitude oriented jet streams with altering regions of lighter colored zones and darker colored bands the orange and brown colors are caused by upward moving material from below that react and change color when exposed to sunlight the light colored zones are richer in crystallized ammonia clouds that hide the deeper darker material below the planet spins once on its axis every 9 hours and 55 minutes the counter rotating jet streams and its atmosphere create vertical storms along their borders there are dozens of these storms at any one time spread out across the entire planet but none are as big or as famous or as old as the great red spot a cyclone is defined as a large scale circulation of winds around a central region of low atmospheric pressure by contrast an anticyclone is a similar circulation of atmosphere around a region of high pressure knowing this matters because anticyclones which the great red spot is have a clearing effect of clouds and high level moisture this means that the great red spot is not an object but a hole it allows us to peer deeper inward [Music] wind speeds of 432 kilometers per hour are produced along its edge and the diameter of this one jovian storm is greater than that of our entire planet [Music] the first official sighting of the great red spot from earth-based telescopes was in 1831 by german astronomer heinrich schwab it was observed periodically throughout the 19th century it may have been spotted as early as 1665 by englishman robert hooke volume one of the philosophical transactions of the royal society page three refers to a quote spot in one of the belts of jupiter though he could have been referencing one of jupiter's four large innermost moons discovered in 1610 by galileo galilei while the precise date of this ancient storm's discovery is controversial what is beyond dispute is the fact that it is shrinking it's only half as large today as it was in the 19th century its future uncertain perhaps it will disappear in our lifetimes perhaps it will experience a resurgence and grow again jupiter's mass is two and a half times that of all other planets in our solar system combined so massive that it causes our sun to appreciably wobble the center of gravity between jupiter and our star lies outside of our star's surface meaning in effect the two orbit each other though just barely as jupiter radiates heat and energy it cools and shrinks it is believed to be the oldest planet in the solar system and when it formed it was much hotter and nearly twice the size it is today jupiter would need to be approximately 75 times more massive for conditions within its core to achieve the proper temperatures and pressures to fuse hydrogen and become a star most stars in our galaxy are in fact binary systems with up to 85 percent of the star systems in the night sky composed of two or more individual stars single stars like our own sun are the exception not the rule jupiter would have been a companion star but it failed to attain enough mass as voyager 1 speeds past it turns its attention to jupiter's moons in 1979 jupiter had 14 known satellites thanks to the voyager spacecraft and others that would come in the future such as the galileo mission jupiter now has over 80 known satellites and that number continues to climb most of these satellites are simply small asteroids but four stand apart these moons discovered in 1610 by galileo bear his name as the galilean moons each one of them a massive incredibly unique world do you remember the taurus of plasma mentioned earlier that significantly deforms jupiter's magnetic field this cold dense plasma slowly moves outward sapped and transported by jupiter's magnetic field and then ultimately carried away by the solar wind something is replenishing it from within the answer to that mystery was discovered by voyager 1 and has to do with jupiter's innermost galilean moon io when galileo first observed io on january 7 1610 it was not identified as its own body until the following night january 8th for the next two and a half centuries it was little more than an unresolved fifth magnitude point of light in astronomers telescopes it wasn't until the mid-20th century that telescopic observations began to hint at io's unusual nature analysis of the wavelength of light reflected from io hinted at a surface dominated by evaporates of sodium salts and sulfur dioxide io orbits jupiter at a similar distance that the moon orbits the earth some 350 000 kilometers from its cloud tops but what makes io truly special is its geologic activity io experiences such tremendous tidal forces from jupiter's gravity that its insides are literally churned it has some 400 active volcanoes and through these it explosively spews out its insides at a rate of at least a thousand kilograms a metric ton every second these volcanic ejections are dissociated into atomic ions and are swept up by jupiter trailing behind io like a massive tail the plasma taurus is composed of matter ejected from io and for outer space it's surprisingly dense at some 500 atoms per cubic centimeter it is in fact small eccentricities in io's orbit that causes such an extreme flux of felt forces and this non-stop expulsion of matter and energy would under normal circumstances eventually allow io's orbit to circularize however io is unable to circularize because of two other galilean moons europa and ganymede these moons are in resonance with io meaning they experience periods of proximity at regular intervals at the same point in space time and time again these encounters with the other moons on one side and jupiter on the other are tearing io apart it is a tortured existence but one which has a profound effect on the jovian system io is tidally locked to jupiter meaning one side always faces its parent scientists suspected io's surface would be pock-marked with craters but instead they find it's almost completely lacking covered in smooth plains dotted with tall mountains pits and volcanic lava flows a variety of colorful features thanks to various sulfuric compounds voyager 1 observes at least nine active volcanoes and photographs several mid eruption before voyager the only known active volcanoes in the solar system uh were here on earth and then voyager flew by io a moon of jupiter about the size of our moon but 10 times the volcanic activity of the earth quite a striking change to realize the earth was no longer the most volcanically active body as io cuts across jupiter's inner magnetic field lines it develops some 400 000 volts across itself and creates an electric current of some 3 million amps this current creates what is called a flux tube traveling along the magnetic field to the upper atmosphere of jupiter where it accelerates charged particles into the atmosphere creating a visible concentrated bright spot within jupiter's permanent polar auroras an electron rain contributing to powerful polar lightning within jupiter's clouds you heard me right io is at least partially responsible for lightning on jupiter voyager 1 experiences a thousand times the lethal dose of radiation for humans as it passes between jupiter and io constant volcanism intense radiation and powerful electric fields make io an unlikely destination for life but this is where voyager turns its attention instead to the second galilean moon europa voyager 1 does not get the opportunity for a close-up at europa but four months later voyager 2 will with a diameter of 3 100 kilometers europa is slightly smaller than our moon its surface is a chaotic crisscross of icy lineae its composition mostly water ice frozen at negative 138 degrees celsius negative 216 degrees fahrenheit at such low temperatures the water ice here is as hard as granite the brownish reddish regions are also water ice though they are dirtied with clay-like materials and salts despite its striking terrain features europa lacks mountains and craters making it the smoothest object in the solar system though it is possible that regions of its surface are covered in icy spikes that resemble stalagmites on a large scale it appears that europa's crust is moving the cracks that permeate its surface are evidence of shearing caused in part by tidal flexing exerted by jupiter and the other galilean moons unfortunately there's a problem because europa like io is tidally locked to jupiter the cracks on its surface caused by tidal flexing should form a distinctive and predictable pattern yet this is not the case somehow the crust is rotating just as tidal forces melt rock within io could those same tidal forces be melting ice within europa there are very few impact craters suggesting that some type of resurfacing mechanic is at work it is believed that the cracks behave much like tectonic plate boundaries on earth with crust material subducted below and new material diverging upward the scientific consensus is that a layer of liquid water or soft ice exists beneath europa's surface and that this drives the mechanical separation and motion of the outer crust the size of this subsurface ocean is unknown as is conclusive evidence of its existence unfortunately even the smallest estimates put europa's solid ice crust at several kilometers thick well beyond the deepest we have ever drilled on earth still there are those who dream of the day we might land on europa and bore down into a warm saltwater ocean full of hypothesized alien life indirect observations of europa hinted at plumes of water vapor though these are likely caused by the bursting of pressurized briny water pockets near its surface there is some level of matter being emitted from europa and cryovolcanism is the likely cause but it is not yet clear if this is correlated to its hypothesized subsurface oceans when the voyager probes and the later galileo mission encountered europa the possibility of life within caused an explosion of excitement since then discoveries around other moons elsewhere in the solar system have surpassed even europa in potential habitability but it nonetheless remains one of the highest priority targets for the seeking out of life elsewhere in our solar system when we think of places you might find life we typically think of the goldilocks zone around a star where water would be liquid in its natural state and if you get a little too close to the star heat would evaporate the water too far away would freeze and neither of those states of h2o are useful to life as we know it we need liquid water so you can establish this green zone this habitable zone this goldilocks zone where if you find a planet orbiting there hey a good chance it could have liquid water let's look there first for life as we know it now it turns out that this source of heat of course is traceable to the sun and if you go farther out everything would or should be frozen all other things being equal but europa a moon of jupiter sitting well outside of the goldilocks zone is kept warm not from energy sources traceable to the sun but from what we call the tidal forces of jupiter itself so jupiter and surrounding moons are actually pumping energy into europa and when you do that to a solid object the solid object is is stressing so you have this frozen world europa completely frozen on its surface but you look at you look at the surface and there cracks in the ice and it shifted and then refroze so this ridge has a discontinuity in the crack and then continues in another place so what this tells you is that europa cannot be completely frozen because if it were nothing would be moving you look at the surface of europa the frozen surface they're like ice chunks that are like shifted and re-frozen and shifted again it looks just like if you fly over the arctic ocean fly over the arctic ocean in the winter these are ice sheets that are breaking and re-freezing all the time it's the same signature as that so all of us are convinced that beneath this icy surface is an ocean of liquid water and there's no reason to think it wouldn't have been liquid for billions of years on earth where we find liquid water we find life [Music] ganymede the third galilean satellite orbits at a distance of just over a million kilometers like io and europa it's tidally locked because ganymede's eccentricity is low tidal heating is negligible however in the past ganymede may have experienced isolated episodes of tidal heating as a result of its orbital resonance with io and europa ganymede is the largest and most massive moon in the solar system larger even than the planet mercury though far less dense clocking in at under half of mercury's mass this suggests a composition of equal parts rocky material and ice the galileo mission would in the 1990s conduct magnetic measurements of ganymede that recorded a significant persistent magnetic field around this moon this suggests that ganymede's core is not frozen yet for an object of ganymede's low density there should not be enough iron to generate such an active magnetic presence furthermore ganymede's magnetic field is constantly shifting somehow it's being amplified the leading model suggests that like europa ganymede may have a massive subsurface ocean the fluid motion of saline water acting as a conductor below the surface that is of course just one theory like with europa there is no direct evidence of a subsurface ocean on ganymede but if the salt water model happens to be true then ganymede's ocean would have to be incredibly large a global layer somewhere between 100 and 800 kilometers thick it would be the largest ocean in the solar system bar none loads more than all the water on earth there are lots of possible models for ganymede's interior don't get too excited though if it does exist it's trapped 95 kilometers below a crust of rock and ice scientists are unsure how ganymede got its grooved terrain which appears similar to europa's this suggests tidal heating but that would be improbable given ganymede's distance from jupiter perhaps it formed much closer and migrated outwards ganymede's surface is considerably older than europa's and is covered in impact craters the surface radiation experienced on ganymede from jupiter is enough to cause severe illness and death after just two months before the voyager missions it was believed that ganymede and the fourth galilean moon callisto were incredibly similar both are larger than the planet mercury both are relatively dark and both are very lightweight there however the similarities begin to end voyager 1 reveals that callisto has perhaps the most ancient surface of any moon or planet in our solar system countless impact craters the result of meteorite bombardment over 4 billion years kept in a state of complete preservation ganymede's surface may only be a quarter as ancient as callisto's there is no evidence of any endogenic processes occurring on callisto now or in the ancient past such as volcanism or tectonic activity as mentioned its low density suggests lots of ice whether or not this ice is partially molten at some deep subsurface layer is hard to say once again certain models support the possible existence of a salty underground ocean based entirely on magnetic data that suggests jupiter's own magnetic field creates electrical currents within callisto this may imply a layer of highly conductive fluid within there is simply not enough good corroborating data to qualify this interpretation which is one of many a significant problem with this theory is that callisto experiences no tidal heating of any kind meaning if there is a thick layer of ice it is likely completely frozen solid perhaps the radioactive decay of heavy elements deep within callisto's mantle provides the heat the question is whether or not the moon as a whole is insulative enough to keep that heat from simply escaping through its crust and radiating outward into space once again we lack enough information one thing that makes callisto an interesting exploration target is the fact that it experiences very low levels of jovian radiation on its surface for those with minds inclined toward science fiction or perhaps just boundless ambition callisto is an ideal base for a human outpost the richness of water ice on its surface holds the promise of drinking water breathing oxygen and the production of rocket fuel as voyager 1 transits jupiter's equator a thoughtfully programmed maneuver points its television cameras out into space across the equatorial plane and exposes it for an incredible 11 minutes and 12 seconds the sheer length of this exposure is almost unheard of nasa is searching for something incredibly dim the squiggly lines you can see are in fact stars they look the way they do because their light on the camera's sensor has been recorded for over 11 minutes the spacecraft's natural oscillation as well as its rapid speed as it flies by jupiter has dragged these points of light across the image frame but that isn't what this photo is showing us look instead at the large band diagonally dissecting the center of the image that is the first ever visible proof of rings around jupiter jupiter's rings are incredibly faint and composed of thin dark dust only one called the main ring is even remotely well defined it is believed that these rings are formed from meteoroid impacts with jupiter's moons careening off streams of fine particles into its orbit its overall age is unknown but it is believed that the average dust particle spends no more than a thousand years in the ring before being sapped away by a number of external forces that act as a drain on the ring itself therefore it must be constantly replenished by new impact events jupiter's rings may be faint and tenuous but they are there the two voyager spacecraft greatly expanded our body of knowledge of the jovian system setting the stage for future missions to build upon their success three new satellites were discovered and a massive host of data was obtained that allows us to characterize this planet and the moons we knew existed but knew nothing about in great detail [Music] despite the earlier problems experienced during the coast phase the voyager mission at jupiter was a tremendous success so successful in fact that it would have an impact on another mission still ongoing it was time for jpl to exact their revenge the half-ton pioneer 11 probe which had encountered jupiter in 1974 was still traveling outwards towards saturn and would reach its closest approach in september of 1979 just a couple months after the voyager probes had rounded the fifth planet and were well on their way to the sixth the two pioneer probes 11 and its sister 10 were a small part of the reason that grand tour was originally cancelled now jpl was in a position to exert its will on nasa's ames team responsible for pioneer since voyager 2 was still on a grand tour trajectory jpl argued that pioneer 11 should be retargeted to fly through saturn's outer a-ring something that voyager 2 would have to do in order to be successfully retargeted towards uranus jpl wants pioneer 11 to be a test dummy sacrificing some of its own scientific objectives to act as a mere forerunner for voyager scientists are unsure of the makeup of the rings at this point and are worried that the spacecraft might be impacted and destroyed by the material within jpl and the voyager team who were unaffiliated with pioneer were adamant that the smaller less sophisticated probe test the route that voyager 2 would have to take the pioneer team for their part argued that the outer path would be too far away from saturn for their spacecraft to take the measurements that scientists were interested in for the first time in this story nasa management sides with jpl they concur that pioneer at this point is a mere prelude to voyager and to the sound of much booing from the pioneer team director of planetary programs tom young announces to the public that pioneer 11 would travel through the outer rings less as a trailblazer more as a guinea pig the voyager team would know soon enough whether passage through the outer ring was feasible they continued to hold onto hope for their extended mission pioneer 11 passes saturn on september 1st 1979 it nearly collides with a previously undetected moon missing by just 2 100 nautical miles some 4 thousand kilometers it discovers another previously unknown moon and charts saturn's magnetic field nasa had given it a 50 50 chance for survival and yet pioneer 11 passes through the ring plane unfazed saturn's rings are nearly 300 000 kilometers across and impossibly thin high estimates placing them no more than 100 meters or 330 feet in width low estimates as thin as just 20 meters or 66 feet it takes pioneer 11 just four fifths of one second to traverse through the rings pioneer 11 may have been primitive compared to voyager but its importance as the first man-made object to reach and study saturn cannot be overstated saturn's equator and rings are tilted 27 degrees to the plane of the ecliptic giving rise to seasons the sun illuminates the northern face of its rings for one half of the year and the southern face for the other half given saturn's incredible distance from the sun it takes 29 earth years for it to complete one full orbit and thus its two seasons last 14 and a half years each its rings acting like a massive sundial casting varying degrees of shadows on its atmosphere 1979 happens to be a year when saturn's rings are in near alignment with the sun meaning the shadow they cast is minimal missions sent decades later such as cassini would capture a wholly different view the two voyager probes are traveling much faster than pioneer 11 and unlike it they would not take five years to reach the planet in fact voyager 1 would encounter saturn just 21 months after it had left jupiter both voyager probes experienced glitches and hiccups as a result of the intense radiation around the fifth planet including but not limited to clock errors photographic artifacting and communications troubles however as they speed away from jupiter they appear more or less unharmed during an attempt to put voyager 1 into a sun canopus alignment its star trackers accidentally lock onto alpha centauri resulting in a temporary loss of downlink voyager 2's polarimeter experiment may have suffered irreparable damage at jupiter with a definite issue in its filter wheel voyager 1's polarimeter had died completely after tests indicated that it had lost all sensitivity to light it is the first scientific instrument between the two probes to be shut down permanently it will not be the last voyager 2's backup mission load which had been programmed into its computer ever since it lost its primary radio receiver is amended now that it has passed jupiter its secondary receiver continues to work well but jpl remains vigilant the outlook for the uranus encounter looks better and better voyager 1 begins its concentrated observations of saturn in late august of 1980 and will pass by the planet in november voyager 2 now 9 months behind will follow in 1981. one major discovery is made right off the bat voyager 1's planetary radio astronomy experiment conclusively measures that saturn spins once on its axis every 10 hours and 39 and a half minutes give or take a few seconds the equatorial regions of its atmosphere can rotate as fast as 10 hours and 14 minutes indicating the presence of high velocity jet streams [Music] don't let saturn's pale hues deceive you wind speeds can reach 500 meters a second that's over a thousand miles an hour saturn is a blender aggressive mixing has eliminated most of its definition but faint bands are still visible of course the most prominent and obvious feature of saturn are its rings saturn is the jewel of the solar system once again galileo can be credited with having first sighted them but others were the first to correctly deduce what they were galileo described the planet as having arms decades later dutch astronomer christian higgins identified them as rings in the 1650s and in the 1670s italian-born french naturalized jean-dominique cassini first described the structure of the rings citing the largest gap which now bears his name the cassini division saturn's rings boast incredible structure and complexity they are mainly water ice carbon and organic compounds there is more to saturn's rings than meets the eye visible only in up sun photographs saturn's g and e rings appear as faint glows encircling the planet but it doesn't stop there at a distance of some 12 million kilometers is arguably saturn's strangest ring the phoebe ring named after the small moon that matches its orbit and from whom it likely originates the phoebe ring is not only massive and nearly invisible it's tilted significantly and what's more like phoebe itself it orbits retrograde opposite to the spin of both saturn and all its other moons the original theory behind saturn's rings is that they are left over material from the original planetary nebula from which saturn was formed surely what is happening now has always happened and will always continue to happen could this be a cosmic hot hand fallacy data from more recent missions such as the massive cassini orbiter suggest that they are instead no more than a hundred million years old meaning that they could have formed a round saturn as a result of impacts between two or more of its moons at the same time that dinosaurs roamed the earth furthermore material from the rings are being drained by its magnetosphere at an alarming rate they may have less than 100 million years to live nevertheless for the short term anyways the rings are highly differentiated highly structured and highly stable they are kept in place by the influence of small so-called shepherd moons that orbit amongst them keeping them in gravitational balance and preventing their spread and dilution the voyagers spot another curiosity in the ring some kind of deformation in the pattern these artifacts nicknamed spokes are likely caused by saturn's magnetosphere electrostatically interacting with very fine magnetic dust particles within the rings causing them to clump together and behave abnormally under the influence of saturn's powerful interior forces saturn unlike jupiter is not reddish in the slightest though as far as composition is concerned the two are very similar both are predominantly hydrogen saturn is around 96 compared to jupiter's 89 saturn has less helium three and a half percent but both have trace amounts of methane and ammonia it is still uncertain to what extent jupiter's red colors are a function of chemical reactions localized entirely within its atmosphere possibly involving sulfur compounds or whether they are reactions with solar radiation either way this process does not appear to take place on saturn it is largely monochromatic with various hues of pale yellow like in jupiter's yellowish zones the color is thought to originate from clouds of crystallized ammonia it has been theorized that below the upper atmosphere exists a series of relatively long lasting dark belts and light zones on saturn one does not have to penetrate very deep into saturn before its hydrogen is compressed into a liquid liquid hydrogen is believed to be its thickest layer making up for well over half of the planet by volume deeper in this hydrogen begins to take on metallic properties and may even be compressed into a solid saturn has a hot rocky core the planet radiates two and a half times more energy out into space than it receives from the sun because of the unique combination of its massive size and rapid spin saturn is the most squished planet in the solar system its polar radius and its equatorial radius differ by nearly 10 percent saturn and jupiter together hold 92 percent of all of the planetary mass in our solar system storms do occur on saturn though they are short-lived and difficult to catch when they do happen they appear as milky white fluid turbulence permeating across the otherwise featureless banded face of the pale planet [Music] saturn's incredible winds are responsible for two of the solar system's greatest oddities at its south pole a fantastic hurricane-like vortex nearly the size of the earth that may have existed for billions of years at its north pole is something far far stranger perhaps the weirdest demonstration of fluid dynamics anywhere in the solar system a permanent hexagonal cap its alien appearance seemingly defies logic it is unlike anything we have ever seen on earth the change in relative wind speeds across saturn's latitudes are the cause adjacent parts of saturn's atmosphere moving at different speeds induce unstable behavior in this case a wave like disturbance this shape and others have been recreated in labs on earth using nothing more than water flow gradients and fluorescent dye not so alien after all another oddity with saturn is its magnetic field which seemingly defies classification on jupiter and earth the magnetic fields are offset from the rotation axis by around 10 degrees the traditional logic holds that this tilt is a natural byproduct of how the magnetic field is generated from currents deep within the planet's interiors without some level of interior turbulence the magnetic fields wouldn't exist it's the fact that the core is not perfectly aligned with the exterior in both spin and spin rate that generates this flux saturn however defies this its magnetic field is almost perfectly aligned with its rotational axis perhaps down to just half a degree likely for this reason saturn's magnetosphere is fairly weak for a planet of its size while its magnetic field is 600 times the size of the earth's overall it is slightly weaker saturn is surrounded by a myriad of unique and interesting moons and thanks to later missions like the cassini orbiter we are aware of more moons around saturn some 83 and counting than we are around jupiter that isn't to say of course there are more but the quality of our data around saturn thanks to cassini has surpassed that of our data around jupiter the voyagers observe several of saturn's incredible moons as they speed through its system there are of course the asteroid like shepherds of the rings pan pandora and prometheus janus and epimetheus these moons are interesting in their own right but perhaps more so because of the utility they play in maintaining saturn's stunning cosmic appearance further out of course you can't miss mimas believed to be responsible for the cassini division it has a massive impact crater on its leading edge giving it a death star-like appearance further out you reach the e-ring that mystical outer glow only visible when looking towards the sun within the e-ring orbits a small icy moon called enceladus in 2005 decades after the voyager flybys the cassini probe would discover the connection long suspected and finally confirmed enceladus has multiple jets of material emanating from its south pole geyser-like plumes of warm salty water enceladus is ejecting massive amounts of salt water laced with grains of silica rich sand nitrogen and organic molecules including trace amounts of simple hydrocarbons to the tune of some 200 kilograms or more every second the two voyager probes imaged the northern face of the small moon and missed the geysers which are almost entirely concentrated near its south pole however the fact that enceladus was embedded in the densest part of the e-ring led many to conclude that the ring was a product of material vented from the moon few could have imagined however that this material would be ideal for life as we know it the water coming out of enceladus geysers isn't just full of organic compounds and silica sand and simple hydrocarbons perhaps most importantly it's warm full of thermal energy the source of this energy is not fully known since tidal heating can only account for some 10 percent of it if that enceladus is very very small with a diameter of just 313 miles or just over 500 kilometers its tiny size and gravity rules out the possibility of a molten core or the presence of heavy radioactive elements deep within these may have been a factor during its initial formation but the mystery remains how has it maintained its heat energy for so long direct evidence of warm water geysers originating from a subsurface ocean places enceladus at the top of the pile in terms of places where life is likely to exist outside of earth surpassing mars and even europa [Music] further from enceladus is icy tethys itself covered with impact craters ranging from the small to the colossal then of course there's rugged diony covered in scars and canyons a world riven by enormous fractures on its trailing hemisphere as you continue moving outward the moons seem to get larger further still from dione is its bigger twin raya each of these moons an icy desolate world their surfaces logging an ancient history of impacts and interactions with rings and debris but from here things take a dramatic turn three quarters of a million miles away some 1.2 million kilometers out from saturn exists its largest and most complex moon a moon that stands apart not just in the saturn system but in the solar system [Music] for hundreds of years it was known as a fuzzy orange ball featureless mysterious unknown titan is the only moon in our solar system with a real atmosphere an atmosphere so thick that despite having a surface gravity only slightly less than that of our moon the atmospheric pressure at titan's surface is one and a half times greater than that of sea level on earth in short titan has a lot of sky and because of its low gravity that atmosphere does not cling to its surface as tightly as earth's does instead it hangs loosely around the moon like a thick outer shell because atmospheres get progressively thinner it's nearly impossible to define a strict upper bound what you i and human law commonly thinks of as space low earth orbit is actually well within its scientifically defined atmosphere and this is why the iss which orbits within the thermosphere layer requires periodic boosting but to give you an idea of how much higher titan sky rises above its surface understand that the opaque orange haze that obscures its surface exists at or slightly above an altitude of 200 kilometers that's over twice as high as the internationally recognized boundary of space the carmen line on earth and that layer of haze is considered one of the lower layers of titan's atmosphere the two voyager probes make valuable observation of titan in their time but the details of its surface will remain locked away until of course cassini and a small stowaway on its side huygens in the mid-2000s the huygens probe separated from the cassini orbiter and became the first spacecraft to enter titan's atmosphere successfully landing on its surface on january 14 2005. in an ironic twist of fate a design flaw with cassini's radio relay firmware led to an issue with doppler shifted data transmitted from huygens not wholly dissimilar from the issue that plagues voyager 2 as huygens descended it transmitted data over two radio channels due to a ground sequencing error cassini was not listening on one of the two frequencies meaning half the data transmitted from huygens was lost despite being plagued with problems compounded by human error on the ground the small probe returned the first images of titan's surface and made invaluable measurements of conditions on the ground titan is an incredibly cold world the temperature at the landing site 180 degrees below zero celsius nearly 300 below fahrenheit amazingly it's a humid world and has stable bodies of liquid on its surface there's lakes clouds and even rain titan has weather it has a climate it's liquid methane titan's atmosphere is over 95 percent nitrogen gas but the haze and humidity is from methane gas 1.5 percent at high altitude and nearly 5 percent near the surface titan's methane cycle is amazingly similar to earth's water cycle it evaporates rises condenses and rains methane lakes on titan are similar in size to the american great lakes they are the only stable bodies of liquid on the surface of a celestial object outside of earth below its opaque haze titan has wispy methane clouds most of its lakes are concentrated near its poles these lakes are dark highly reflective and very very cold there's no risk of fire here because there's no concentration of oxygen here titan has hundreds of times more liquid hydrocarbons than all known oil and gas reserves on earth but unlike on the earth these formed abiotically likely a result of ultraviolet radiation from the sun which knocks hydrogen atoms off of stable methane molecules in the atmosphere to form highly reactive methyl radicals that then react with each other to form more complex compounds like ethane and propane endless combinations of carbon and hydrogen that together make up a vast complex climate on titan conditions on titan's surface are very close to the triple point of methane meaning it can coexist as a solid gas or liquid and tiny variations of energy and pressure across small distances can result in phase changes the exact composition of titan's lakes are unknown but it is believed they are a mix storing the concentrations of the heavier hydrocarbons like propane and ethane along with a bulk volume of liquid methane it's even possible that solid methane ice full of nitrogen gas bubbles could be floating on the surface of these lakes but this has not yet been confirmed the rate of evaporation on titan is incredibly low but its thick atmosphere can hold a lot more liquid before rain forms aided by low gravity as a result it is believed that titan experiences long periods of relative drought lasting decades or perhaps centuries followed by torrential hydrocarbon rains and flash floods that impact the surface on a global scale and then we flew by titan which is the fuzzy ball you see here which has 50 higher pressure nitrogen atmosphere than here on earth but has methane natural gas in the atmosphere not oxygen so the action of sunlight is to create complex organic molecules which create this haze that cannot be seen through in the visible fortunately the cassini mission appeared several decades later with a radar system that could look through the clouds through the haze and saw that deed there are lakes of liquid methane liquid natural gas on this moon perhaps resembling what the early earth may have looked like before life evolved observation of titan was considered a key objective for voyager 1. so much so that its trajectory around saturn optimized specifically for proximity to titan prevented it from continuing on to uranus or neptune this is where the journeys of voyager 1 and voyager 2 diverge throughout the mission it remained a possibility to retarget voyager 1 away from titan and instead use saturn's gravity to throw it towards pluto and it would have arrived in 1986 instead titan was deemed a much more valuable exploration target and pluto would remain unvisited until the new horizons probe flew past it in 2015 this was the ultimate moment of decision had voyager 1 failed to image or make measurements of titan voyager 2's extended mission would be cancelled and it would be retargeted towards the small moon but luck was on jpl's side voyager 1's titan observations were deemed satisfactory and voyager 2 remained on its grand tour path voyager 1 is flung above the plane of the ecliptic by saturn on a journey that would not take it near any planets ever again as it leaves the saturnian system it photographs the outer satellites multicolored iapetus stained from ring material and the elusive retrograde phoebe orbiting within its own faint ring that would remain undiscovered for decades it's always gratifying to have the results be something more than what was expected and saturn and what we have found was not expected i suspect even for the next few years we will find new discoveries in the data which we've acquired in the last few days and as we see more and more examples of the way the universe can put planets together we find that our terrestrial perspective in explaining our own planet has been rather limited we get new ideas from this what we learned about saturn during that encounter and during the months that preceded it have really rewritten the textbooks on saturn the voyager probes encounter with saturn were far from definitive but they provided a first glance at the environments that missions like cassini would later study in detail by january of 1981 the planetary exploration phase of the voyager 1 spacecraft had ended no more worlds lie before it however it was not shut down or turned off now testing the interplanetary waters it continued on studying the sun as it began a long open-ended mission out of the solar system because of the encounter with jupiter and saturn it was now too far and traveling too fast for the sun's gravity to hold it in scientists were pretty confident that our sun's magnetic field though much much stronger was fundamentally similar to the magnetic fields of the planets they knew at some point the particles streaming outward would bend and arc backward blunted by the interstellar wind the combined radiation pressure of all the other stars in our galaxy in 1981 jpl hypothesized that voyager 1 might cross this boundary in 1990 at a distance of 40 au 40 times the distance between earth and the sun they had no idea how large our meager star's influence really is voyager 1 would not cross this boundary until it had reached a distance of 122 au or 18 billion kilometers away in 2012. by then an entirely new generation of scientists had matured and were working with voyager many of them too young to remember a world before its discoveries mapping and measuring the outer layers of our star's magnetic field and how the solar wind interacts with the galaxy is the underlying principle of the voyager interstellar mission which continues to this day the magnetic field lines are showing us how the magnetic field is wrapping around this helipod surface and we believe that what voyager is telling us is as it propagates farther away from the sun it's going to tell us more about how far this interaction goes but then the magnetometer people came along and said but you know the magnetic field direction didn't change at all so that would mean that the sun's magnetic field and the galaxy's magnetic field were lined up and that didn't seem likely then the plasma wave team came to the rescue the sun sent out some big blast waves had sent out some big blast waves and they reached the vicinity of voyager 1 and it caused the plasma to oscillate and the plasma wave experiment measures the frequency of those oscillations and it turns out if you know the frequency of those oscillations then you know the density of the plasma and turns out the density that is inferred is the density expected in interstellar space and not inside the heliopause so that's when we knew that voyager 1 had gone interstellar and by the way modelers and theorists are coming to grips with the magnetometer data and figuring out that why that happened and it's just the interaction between the heliosphere and their cellular medium was a little more complicated than we first thought [Music] [Music] on august 25th 1981 as voyager 2 was an extremely close proximity to saturn in its shadow and out of communications with the earth its scan platform became horizontally stuck the problem wasn't discovered until communications were re-established and after realizing that it was serious the ground team immediately issued commands for it to elevate its instruments away from the sun to prevent damage to the sensitive optics of the various instruments on the platform this error caused the loss of several planned observations as most of the outbound trip was spent troubleshooting this new issue by august 28th the platform's azimuth actuators started moving again though its response time was hesitant and slow for several weeks science activity aboard voyager 2 is curtailed as the ground team conducts hesitant tests concluding that it is likely the symptom of a mechanical problem within the spacecraft and not the result of any external factors the voyager team does not let go of their grand tour dream and on september 23rd 1981 they finally acknowledge publicly and in writing that they plan to conduct a small mid-course correction burn such that the uranus flyby places the spacecraft on a course towards neptune the long chain of decision is now complete the spacecraft simply has to survive long enough to make it there significant changes would have to be made in order to support voyager 2's extended mission the signal strength alone would be a quarter at uranus of what it was at saturn and even that wasn't much at all the solution was to array antennas together utilizing multiple large radio dishes in simultaneous operation several antennas were physically enlargened voyager 2 had a profound effect on the current state of the deep space network inadvertently creating a state-of-the-art facility for planetary radar astronomy voyager related upgrades resulted in the creation of a powerful scientific instrument on the ground in its own right scientists have used the radio telescopes in their current configuration to remotely study the planets without the help of probes like voyager leading to discoveries such as the existence of polar ice on mercury voyager 2 scan platform issue is narrowed down to a problem of lubrication and worn gear mechanisms its movement is conserved and the prospects for a uranus encounter are good an outer space spectacular that was the stuff of dreams only a generation ago began snapping under the sharp focus of reality today after its billion-mile journey from earth the voyager spacecraft sent back pictures of man's closest look yet at the ringed planet saturn the spacecraft trajectory is controlled by radio tracking the spacecraft coming up with position information from the radio data and from the use of photographs that we take of the satellites against the star background we convert that data into position information then that's combined with the radio data that position information allows us then to compute the maneuver that we put into the spacecraft in terms of the angles that we turned through using uh small hydrazine rocket engines two tenth pound thrust engines all of those maneuvers have been very precise the initial trajectory is very precise so the some 230 pounds of fuel that we had at launch is more than adequate and there would be ample fuel left over after saturn to continue flying the spacecraft out of the solar system uranus was not discovered until 1781 when british astronomer sir william herschel recognized it as a solar system object up to that point uranus may have been misidentified as a star by various individuals cultures and civilizations across history and likely shows up in several ancient star catalogs herschel at first believed it was a comet what to call this new planet was something of a controversy throughout the first half of the 19th century herschel wanted to name it after king george iii and many english institutions royal societies and universities referred to it from there on as georgian cities latin for george's star unsurprisingly this name was decidedly unpopular elsewhere throughout the western world german astronomer johann beaud proposed uranus and by 1850 the last major english institution that had held onto the original name finally gave in uranus is the only planet other than saturn whose rings are observable from the earth though not without advanced technology uranus's rings were discovered the same year voyager 2 was launched in 1977 aboard a flying observatory operated by nasa that witnessed uranus passing between earth and a distant star causing unexpected infrared fluctuations uranus's rings reveal another oddity about this world the first of the two ice giants it's on its side all planets in the solar system rotate essentially on the same axis conserved momentum from the original protoplanetary disk in which they formed venus either as a result of tidal forces or a massive impact spins backwards relative to the other planets but nonetheless along the same axis of rotation uranus however is arguably stranger the planet is tipped onto its side its spin rings and moons are tilted 98 degrees from the plane on which it orbits the sun the ecliptic the current consensus is that uranus's tilt is a result of a massive traumatic impact early on in its formation when our solar system formed it is likely that hundreds of planetesimals condensed from the protoplanetary disk what followed was a game of celestial bumper cars as bodies competed for space throwing crashing into and absorbing each other uranus may have suffered a glancing blow that rocked the planet over onto its side and the fact that its moons orbit along its displaced equator tells us that they likely formed as a result of or after this collision scientists now believe that all of the outer planets after their initial formation began moving much closer to the sun than they are now and it was a dramatic fight a showdown of gravity between jupiter and saturn that eventually threw them back outwards uranus is thought to have been at the beginning of our solar system the outermost planet it was passed by neptune at some point during this era of wild orbital migration evidence for this is corroborated both in computer models and recorded on the surface of our moon as a temporally localized period of intense bombardment by meteoroids that were likely flung inward as these ice giants moved outward it is possible there may even have been more planets than there are today and these planets might still exist ejected from the solar system outright rather than destroyed or absorbed like outcasts they could wander the milky way far beyond the solar system in which they formed could our celestial neighborhood be populated by dim dark wanderers that once called our sun their home wherever and however it formed uranus exists now at an average distance of 19 astronomical units fluctuating down to 18 and up to 20 due to its eccentric orbit at a distance of 2.6 billion kilometers uranus takes just over 84 years to make a complete circle around the sun it spins once on its bizarre axis every 17 hours and 14 minutes each pole experiences 42 earth years of uninterrupted sunlight followed by an equally long period of desolate darkness as voyager 2 encounters uranus in january 1986 it observes a featureless pale blue sphere artificial over saturation of images reveals that uranus does in fact have subtle differences in brightness across its latitudes but to voyager uranus by all accounts looks like a dynamically dead planet modern imaging techniques have revealed more to uranus than originally met the eye its appearance seems to be changing as its position around the sun changes several clouds have been spotted some may have existed for decades the planet takes on much more detail when studied in different wavelengths of light beyond simply the visible spectrum the key to understanding uranus is incredibly slow seemingly dead appearance is the lack of thermal energy within its internal heat is notably lower than that of the other gas planets it hardly radiates any heat energy into space whatsoever and temperatures within its atmosphere are as low as 49 kelvin or in fahrenheit 371 and a half degrees below zero 49 kelvin that's 49 degrees of celsius above absolute zero this may be further evidence of a massive impact in uranus's past which might have caused it to expel most of its primordial heat as it broke apart and reformed alternatively some sort of barrier may exist that prevents heat from the core from reaching the outer layers of the planet like jupiter and saturn the bulk of uranus volume is believed to be a thick layer of compressed gaseous and liquid hydrogen deeper down however it likely diverges from this model with solid water methane and ammonia ice forming a type of mantle over a small rocky core a tiny concentration of methane in its upper atmosphere less than three percent is responsible for the planet's bluish color oddly enough the space immediately around uranus is hot gas particles in its thermosphere reaching nearly 850 kelvin how this heat is sustained at all is not understood all measured variables including solar radiation and magnetic field activity do not even come close to accounting for this phenomenon speaking of magnetic fields uranus unsurprisingly has one of the strangest not only is it tilted nearly 60 degrees away from its axis of rotation that does not seem to originate from the center of the planet it is nearly 10 times stronger in the northern hemisphere than it is in the southern hemisphere this suggests that mechanics totally unknown in the history of human experience are at work perhaps these magnetic fields are generated by the convection of conductive material much closer to the surface than in the case of earth or jupiter alternatively it may be a normal magnetic field that is somehow redirected an effect called magnetic shielding by some substance concentrated in its southern hemisphere one possible material that might offer this property is diamond highly compressed carbon existing at extreme depths within uranus a compressed carbon ocean at certain depths this carbon may crystallize into solid gigantic iceberg sized diamonds and float upwards these proposed diamond bergs are just one speculative way we have tried to answer the nagging question of uranus mystifying magnetic field the thing is we just don't know voyager 2 the only spacecraft to have ever visited uranus is not equipped with the kind of sensitive sophisticated remote sensing instrumentation we would need to unlock the secrets of the ice giant's interior it's important to keep in mind that many of these exotic claims while scientifically valid solutions are not observations in and of themselves they are but one possibility among many that may explain why we've measured what we have measured often the most exotic and exciting possibilities are held above the seemingly mundane human expectations are often difficult to temper because voyager 2 is passing uranus nearly dead on from its rotational axis it will be piercing through the plane on which its moon's orbit as opposed to traveling along it as was the case with jupiter and saturn the time that voyager 2 has to make observations is exceedingly limited it will have only five and a half hours to make observations that for previous planets it may have had 30 or more voyager 2 will reach its closest approach to all of uranus's moons essentially simultaneously it won't be able to leisurely switch from one moon to another as it travels outward it has to get all the data it can as fast as it can the voyager 2 near encounter with uranus occurs at 10 am on january 24th 1986. four days later on january 28th an unrelated incident will distract the world from this amazing unprecedented exploration but the signal to launch was given and everything was apparently on course up to a minute from liftoff when the challenger was turning on the full power of her main engines explosion appeared to come from one of the solid rocket boosters which supply most of the power for the liftoff and were then to separate instead the entire space vehicle disappeared in a fireball the challenger disintegrated and plunged downwards in spiraling debris the shuttle challenger on its tenth mission sts-51l breaks apart during ascent killing its entire crew of seven this happens the same week as voyager 2's uranus flyby but what interest did exist comes screeching to a halt as the nation mourns the loss of seven astronauts the shuttle program only in its fifth year of space flight is put on a nearly three-year hiatus uranus is so far from the sun that light levels here are 400 times dimmer than they are around earth in order to get useful images voyager's cameras have to keep their shutters open for a longer period of time the scan platform slews not in one progressive fluid motion but rather in dimensional steps elevation azimuth elevation azimuth therefore it unfortunately cannot be used to maintain a precise pointing lock on a celestial object for a prolonged period of time the result would be little more than a smeared image especially knowing the precision errors already inherent in the scan platform itself several operational changes are made for the uranus encounter and one of them includes purposefully using the gyroscopes within voyager's guidance system the voyager team will use the hydrazine rcs jets to aid the scan platform and target tracking by moving the bus of the spacecraft itself this strategy would be much more costly in terms of fuel consumption but to the voyager team it was worth the risk this would be humanity's only chance to get a good look at the seventh planet and its moons radio signals from this distance traveling near the speed of light take two and a half hours to reach the earth commands sent from the ground take the same amount of time to reach the spacecraft voyager takes a series of long exposure images of uranus as it approaches and captures views of its epsilon ring note that the spacecraft is imaging the rings head-on due to the tilt of the planet [Music] the spacecraft also images and studies as much as it can what were at the time the five known uranian moons miranda ariel umbriel titania and oberon uranus's moons fall under a separate set of naming conventions than do any of the other major celestial bodies they are not from the ancient greek or roman pantheon but rather are the names of characters from playwright william shakespeare or poet alexander pope a holdover from its decidedly english origin of discovery uranus's moons are small and very dark the largest titania is less than half the size of our moon with a diameter of under 800 kilometers we know now of at least 27 natural satellites of uranus but these five remain the most important it is likely that they all formed as a result of the massive impact that toppled uranus over which may explain the remarkable similarity with each other the innermost and smallest of these moons miranda is unique both for its tiny size and chaotic topography when you look closer you see that significant morphing of its surface has occurred if one measures the distance between the highest highs and the lowest lows on the surface of miranda this tiny moon with a surface area slightly less than that of saudi arabia has the largest cliffs and deepest canyons in the solar system its surface is clearly ancient with impact craters almost everywhere and yet clearly another mechanic is or was at play could miranda have experienced tidal heating in its past when its orbit was more eccentric than it is today could it be a site of active cryovolcanism these are unresolved questions that voyager 2 created when it observed the tiny moon in detail for the first time and only a revisit by a dedicated exploration mission can hope to answer that's right the people here in the space flight operations facility are only one small part of the effort to keep voyager 2 doing the job it was sent to do we shouldn't all forget those people who are not on camera every day voyager like any space project is a team effort and when this encounter is over late next month voyage will be on its way to an encounter with neptune of course the eighth planet from the sun and these people you're seeing here will still be here keeping an eye on their spacecraft voyager's neptune encounter will bring the planetary exploration program to the end of its first major phase that being the initial reconnaissance of the solar system while we've learned so much from the mariners and the vikings and the voyagers we still have a lot to learn and the people who fly these spacecraft as well as the scientists who reap so much from the data we get are our teachers [Music] very recently the planetary science and astrobiology decadal survey published as you might expect every 10 years recommended to nasa and the congress that the next large-scale flagship robotic mission to be developed sometime before 2032 should in fact be an orbiter designed to explore uranus and its satellites not a flyby like voyager 2 but a probe like cassini large sophisticated and able to make detailed and sensitive measurements in orbit over an extended period of time uranus occupies a unique position right now in the realm of planetary science it is a high priority exploration target and it is likely that we will see a dedicated mission to this planet in our lifetimes though that process has only just begun and any results are likely decades away these surveys of which there are many separated by subject and discipline represent the general views of research institutions and academia and they form an important mechanism of advisement for policy makers than those with the power of the purse their views and recommendations are exactly that only time will tell whether this survey's main wish is approved and funded uranus's orbit was calculated in 1783 by pierre simone marquis de la place certain irregularities in uranus's orbit observed over the next several decades could not be accounted for unless it was affected by a body of similar gravity outside its own orbit in 1841 english astronomer and mathematician john couch adams set out to calculate the position of said planet if it indeed existed at the same time but unknown to atoms a french astronomer and mathematician urban le verrier was independently coming to exactly the same conclusion by 1846 le verrier believed he had calculated the position of this unknown mystery body adams's work had sent the british observatories into a frenzy and they searched all over the night sky for this purported eighth planet atoms had sent them six possible solutions where this body might be found levelier however narrowed it down to just one he published his own predictions in august 1846. lavellier was greatly disliked at the paris observatory where his ambition and drive for efficiency had made him very unpopular frustrated and desperate he wrote to johann gale director of the berlin observatory on september 18th on receiving the letter just five days later gale searched for the new planet that very evening he found it that night within one degree of the predicted position like uranus it had been previously cited by telescopes and classified as a star observations made over a four-day period absolutely established a proper motion and thus neptune was discovered a german discovery from a french calculation despite the fact that it had been observed by telescopes previously no one had thought to identify neptune as a planet it is so faint and so far away that it cannot be seen under any other circumstances and its existence was entirely unknown to ancient cultures and civilizations the successful prediction and discovery of neptune showed that isaac newton's gravitational laws were relevant across tremendous distances [Music] as voyager 2 travels further and further away from the sun it slowly loses its ability to navigate and align itself into attitude lock to voyager our star simply gets dimmer all the time voyager 2 increasingly begins using its cameras to send back attitude information specifically long exposures designed to reveal stars nearly 100 photos are taken of space between saturn and uranus for the purpose of optical navigation and more than that are taken between uranus and neptune as voyager 2 approaches it takes several long shots in neptune's direction blemishes and rousseau marks are removed the natural rotation of the probe is accounted for and the points of light are catalogued points that have moved between image frames more than what can be accounted for by the rotation of the probe are classified as newly discovered moons there is so little light out here that the camera's shutters remain open for much much longer than they otherwise would need to be around earth the voyager ground team is forced to get very clever in how they manage the rotation of the probe it was never part of voyager's design to be able to stop all angular momentum there are simply too many moving parts for this to be a feasible expectation not just the articulation of the scan platform but even things as small as the starting and stopping of the tape recorder inside the probe can impart tiny impulses that have a collective effect over long periods of time software changes are made to reduce scan platform motion enhance the gyroscope turn rate and several others in the service of reducing spacecraft motion to accommodate increased image exposure times without incurring excessive smear compensating for the rotation of the probe to facilitate accurate imaging is a central focus of the voyager ground team in the late 1980s the light levels at neptune are only 40 percent of those at uranus the planet as a whole 900 times dimmer than earth image smearing as a result of these incredibly long exposure times represents a serious hazard to voyager's optical data gathering ability they have to be able to get good photographs it's practically the entire point of the mission for that they need voyager to be as solid as a rock not an easy task when it's hurtling through untraveled space voyager 2 encounters neptune in august of 1989 what would be its final planetary encounter since the probe's trajectory after neptune would not really matter the ground team makes a mid-course burn in 1987 to position the probe over neptune's north pole allowing it to fly past its largest moon triton unlike jupiter saturn or uranus neptune has only one major moon triton contains 99.5 percent of all measured mass in orbit around neptune the 13 other recognized satellites are universally tiny asteroid-like objects it's smaller than our moon it's much colder 390 degrees below f fahrenheit and so cold that the nitrogen is frozen into an icy polar cap that you see the white polar cap in the south is nitrogen ice but the dark streets are geysers erupting and depositing on and found two active geysers at the time we flew by on a world that is so cold that even the nitrogen is frozen so voyager time and time again caused us to greatly expand what we knew about plot we knew about planets what we thought we knew about rings what we thought we do about magnetic fields what we thought we knew about moons it's just changed and created a legacy of discovery now for many future missions to the outer planets neptune unlike uranus has a fairly standard axial tilt it experiences the same seasonal variations as a result of this tilt though because of its incredible distance the numbers are staggering it takes neptune 164.8 earth years to circle the sun no human that has ever lived survived through a single neptunian year in fact only just recently in 2011 has neptune completed one full orbit since its discovery neptune like uranus is considered an ice giant it does not have a solid surface but like all the gaseous planets instead has several layers with a large gradient of pressure and phases of matter as you travel inward there are multiple ways you can measure the rotation of a planet like this for instance you can map the shape of its magnetic field and determine how rapidly it's spinning however this spin is often different from that of its atmosphere and since there is no visible surface the rate at which that atmosphere rotates is different depending on the latitude the equatorial regions of neptune's atmosphere seem to make one full rotation every 18 hours but its magnetic field rotates every 16 hours unlike uranus neptune is radiating a significant amount of heat and energy into space and this energy powers a vibrant and active weather system in its atmosphere slightly more massive than uranus neptune is decidedly less hazy with cloud formations and storms visible within like uranus neptune's outer layers are predominantly hydrogen and helium somewhere near an 80 to 20 percent ratio also like uranus a very small concentration of methane gas in the upper atmosphere gives it a bluish color neptune's upper atmosphere is slightly more transparent than that of uranus we now know from further study that uranus boasts cloud features and banding almost identical to what we can see with visible light on neptune a higher concentration of upper atmosphere methane combined with a thinner icy haze layer both a likely result from higher ambient energy on neptune contribute to a deeper darker blue and more visible detail the white clouds are likely concentrations of methane ice particles voyager 2 observes a couple circular storms the largest of which comes to be known as the great dark spot like the great red spot on jupiter this is an anti-cyclone a region of high pressure a hole in the haze revealing darker layers underneath unlike the great red spot which while shrinking has existed for hundreds of years by the time neptune was imaged again by hubble in 1994 the great dark spot had completely disappeared others have emerged in separate locations suggesting that these circular storms have much shorter lifespans but routinely appear the mechanism by which they form and dissipate is not yet fully understood neptune boasts the fastest winds of any planet in the solar system even faster than the transonic belts of saturn near the equator prevailing westward jet streams moving against neptune's eastward rotation were clocked at nearly 600 meters per second or 1300 miles an hour neptune may be 50 percent farther from the sun than uranus and may receive only 40 percent of the relative solar energy but its internal energy radiating upward through its atmosphere drives the fastest and most dynamic planetary winds in the solar system neptune has a strong effect on the shape and size of what lies beyond the kuiper belt an outer asteroid belt that lies just outside of its orbit neptune's gravity maintains the kuiper belt which without it would likely have coalesced to form a remote icy planet there are several dwarf planets that call the kuiper belt their home objects like orcas haumea and pluto their development early on was very likely by the unexpected arrival of the mighty neptune into their backyard neptune did not form all the way out here it migrated fairly late into the formation of the solar system the kuiper belt as it exists today is nearly 20 times larger than the inner asteroid belt and is home to some of the weirdest and most ancient celestial bodies in the solar system in a totally unexpected find neptune's magnetic field like that of uranus is oriented at an extreme tilt relative to its axis of rotation and like uranus does not appear to be uniformly strong around its center of mass it is offset from the center by nearly half of neptune's radius even more extreme than that of uranus scientists had believed that uranus's tilted magnetosphere was a result of its sideways orientation but now it seems that's not the case as neptune also shares this phenomenon it must therefore be some internal mechanism present on both planets driving this bizarre anomalous magnetic behavior voyager 2 studies neptune's large retrograde moon triton not only does triton orbit counter to neptune's rotation but its orbit is also inclined away from this axis of rotation significantly because of both of these factors it is believed that triton did not form near neptune but was rather captured by it this is supported by mathematical models that suggest that triton is slowly spiraling inwards and will eventually pass neptune's roche limit far into the future breaking up into a brilliant ring system before ultimately impacting neptune's atmosphere triton's surface appears to be marked by extraordinarily varied terrain some of which has not been seen on any other body a peculiar landscape of circular depressions rugged ridges impact basins craters smooth plains frosty deposits and cantaloupe terrain how did a moon develop such interesting and dynamic topography the answer may be cryovolcanism the eruption and overall modification of landscapes driven by volatiles such as water methane or ammonia some 55 of triton's surface what voyager 2 was able to directly image at least was covered in frozen nitrogen in this regard triton is very similar to pluto however triton seems to lack the dark reddish hydrocarbon sludge that we see on pluto it should be noted however that one whole side of this intriguing moon remains unobserved equally important telescope observations of triton in the 1960s seemed to indicate it was reflecting a much larger amount of red light than it was when voyager 2 ultimately flew past it in 1989 the appearance of the moon may have altered considerably in the intervening time due to cryovolcanism it may even look very different today than it does in these 30 year old photographs as voyager 2 images neptune with the sun behind it like on each of its planetary encounters before it discovers new and unseen rings these images are the result of 591 seconds of exposure a nearly unheard of amount by earthly standards nearly 10 straight minutes of uninterrupted light gathering as voyager 2 pulls away from neptune in 1989 its planetary phase comes to a close like its sister voyager 1 it begins what is called the interstellar phase of its mission for the remainder of its life it will make observations of our star as it travels ever further mapping and measuring the sun's magnetic field much as it did those of the planets each voyager spacecraft carries on its side a gold-plated 12-inch two-sided stereo phonograph record enclosed within a record case alongside a small stylus designed to read and play back the audio information embedded in each record these records known as the golden records can trace their routes back to pioneer 10 and 11. an english journalist named eric burgess believed that the two pioneer probes which themselves were bound to interstellar travel should carry a message for extraterrestrial intelligences he took this idea to a well-known and very vocal nasa advisor a professor at cornell university and director of its laboratory for planetary studies dr carl sagan in the 1970s carl sagan would rise to national prominence as a science communicator and advocate for the search for extraterrestrial life working in his advisory role for nasa he garnered significant influence over american robotic space exploration sagan was so taken with the idea that the pioneer probes should carry a message from humanity that he was able to convince nasa to incorporate a small lightweight plaque onto the two vehicles sagan would expand on this idea considerably for voyager borrowing several symbols from the pioneer plaques the voyager record covers are essentially a blueprint a list of instructions that if followed would allow an alien intelligence to unlock the contents of the records themselves carl sagan was never considered a member of the voyager team and the golden records did not contribute to their mission his influence over nasa's operational affairs is to some controversial few if any actually expect voyager's golden records to ever be found and read the probes are celestially speaking tiny and dark they emit no major radiation and are many degrees of magnitude smaller than even a small asteroid what these records instead represent is a level-headed attempt to develop a system of communication that is free of any cultural or circumstantial influences the challenge facing sagan and the golden record team was how do you communicate complex ideas without any cultural or biological frame of reference whatsoever what concept would an alien intelligence have of time they wouldn't know what a second was a minute an hour instead the golden record team would have to rely on universal constants numbers and figures derived solely from the cosmos the most important symbol on the golden records cover can be found on the bottom right two hydrogen atoms each just one proton and one electron the hydrogen atom on the right has its electron facing outwards and the other depiction shows its facing inwards in a neutral hydrogen atom at its lowest and most basic energy state the proton in its nucleus and the lone electron in its valence shell spin in opposite directions that is to say their spin is anti-parallel however if a small amount of energy is introduced into this system say from a collision with another atom or from radiation the electron can become excited and enter a slightly higher energy state whereby its spin aligns with that of the proton at the nucleus in this higher parallel energy state the electron and the proton are now spinning in the same direction eventually that energy has to be dissipated when that happens is seemingly random subject to the forces of quantum mechanics of which we understand very little but sometime in the next 10 million years that electron will suddenly and spontaneously drop back down to the ground state and a small amount of energy will leave the atom in the form of radiation a radio wave randomly emitted from excited hydrogen atoms pervades the universe it is found practically everywhere it is incumbent on no one planet or star or phenomenon it is truly omnipresent the line you see that divides these two hydrogen atoms measures 23 centimeters across on the record cover and this wavelength in hertz represents the fundamental unit of time in which all the other symbols here are represented in binary code others on youtube have explained the records far better than i can and i encourage you to watch those videos links below the information embedded within the cover communicates a step-by-step process towards playing and understanding the golden record the first side of the stereo record is fairly straightforward it contains music greetings and the sounds of animals and nature the second side however is much more interesting it is a series of varying tones each separated by an audible beep [Music] these tones are images encoded in audio signals the pitch in tones corresponds to brightness values and the timing corresponds to location these images are meant to be displayed on a classic standard definition crt television 512 lines of resolution each line 8.3 milliseconds each image 4.2 seconds worth of audio because the record is in stereo the images are played back two at a time with two streams of audio relaying separate information people like ron berry using modern digital technology have followed the record covers instructions and have unlocked the content hidden within side b showing that the method of encoding remains relevant even today even if an alien intelligence found voyager which nearly every measurable reason suggests is impossible one can't know whether sagan and his team would ultimately have been successful in their attempt at communication what it does represent however is a template for future generations of humans to build on it was the approach developed not the record flown that ultimately served the experiment's purpose the first successful interplanetary mission of the human species was the marina 2 nasa spacecraft which flew by venus in 1962. the voyager 2 flyby of neptune occurred last year that is 1989 in those 27 years the human species has flown close by or orbited or landed on every one of the planets we have completed the preliminary reconnaissance of the solar system there's only one time in history when this happens when for the first time humans send their artifacts and themselves off the earth and explore their local neighborhood in space it's our great privilege to be alive at that first moment think of the number of objects that we now know are in the solar system that we didn't even know existed then then think of how many were mere points of light where we had no idea what the surface uh features or any details were and then think of how wrong we were in uh in our guesses about uh so many of the objects that we we did know thought we knew something about voyager and viking have wholly changed uh our knowledge of the solar system not of course the celestial mechanics of the of the planets there are a few verities but everything else is kind of prehistoric the the history of real knowledge of the solar system begins in that uh 1975-1989 period now of all those worlds including the 56 moons that the two voyagers explored that dr stone mentioned uh we have no indication of life there are the stirrings and intimations if you like where it's very clear that complex organic molecules are being formed but there is no evidence not a smidgen of evidence suggesting life anywhere else and for me that underscores the rarity and preciousness of the earth and the life upon it also thanks to carl sagan in february of 1990 voyager 1 at a distance of 40 a.u turned its cameras inward and photographed a pale blue dot of light its last look at the earth before its imaging system was powered down to me the mission has personal relevance not because i was ever involved with it but because as a child the encounters with the various planets actually the two final planets uranus and neptune helped to define my childhood and also helped to define my own understanding of our place in the solar system i was too young to enjoy the flybys of of jupiter and of saturn but uranus and neptune i remember quite clearly as a kid seeing the images on the news at in the evening news and just really being impressed by what we were doing out there in the solar system that i could feel that i was one of the first to see these planets in such great resolution and i'm sure that several others of you who like myself perhaps were born in the 70s might feel the same way voyager 1 was actually launched second but it is traveling the fastest it's the furthest spacecraft from us it travels at 38 000 miles per hour approximately nothing's going to catch up to it and voyager 2 is traveling a little bit slower 34 000 miles per hour approximately but that's still 40 times the speed of sound here on earth the voyagers are healthy and as healthy as senior citizens can be that's the way i like to think of them their twin spacecraft identical and think of them as twin sisters senior citizen sisters so each has had different elements over the years the two voyager spacecraft are still alive right now though over the years as their nuclear fuel source has decayed and their power output has diminished the instruments and heaters on board have been shut down one by one they are operating now as a fraction of their former selves but continue to make observations of charged particles in the space around them both probes finally traversed the boundary between the solar wind and the interstellar wind decades after it was predicted they would in space for 44 years and counting voyager 1 the furthest man-made object from earth is 156.5 astronomical units from the sun at the time of this video's production [Music] 156 and a half times the distance between earth and the sun 21 and a half light hours it is expected that the probes will continue to operate until 200 au in the early 2030s both voyager probes have surpassed all expectations their contributions have single-handedly shaped our knowledge of the solar system and the universe their data both old and new lives on in the contributions and interpretations of new generations of scientists and artists these two robots represent the best of us our highest ideals our highest ambitions their story ongoing the history preserved [Music] you

Channel: Homemade Documentaries

Views: 1,196,747

Keywords: voyager space probes, NASA, voyager, jupiter, saturn, uranus, neptune, planetary, space, exploration, history, voyager 1, voyager 2

Id: M62kajY-ln0

Length: 164min 53sec (9893 seconds)

Published: Sun Jun 12 2022