Juno on its way to Jupiter!

By Phil Plait | August 5, 2011 11:19 am

Riding on a plume of fire from its Atlas V rocket, the NASA mission Juno launched at 16:25 UT (12:25 Eastern US time) on its way to Jupiter.

Juno will take 5 years to get to Jupiter, taking the 3 billion kilometer scenic route. In October 2013 it will actually pass the Earth once again, using the gravity of Earth and its motion around the Sun to steal a tiny bit of our energy and propel it to the outer solar system. From here, it will take a wide elliptical path to the giant planet, which orbits the Sun 5 times farther out than the Earth does. That’s why it takes so long.

Once there, it will orbit Jupiter for about an Earth year (how cool and science fictiony is it be able to say that?), taking its measure of Jupiter’s atmosphere, composition, surrounding environment, and magnetic field. It’s equipped with microwave, ultraviolet, infrared, and visible light detectors (which means very high-resolution pictures!) as well as other instruments to try to understand this enormous planet.

Interestingly, Juno is using solar panels for power; sunlight is only 4% as strong at Jupiter as it is here on Earth, so it’s only been through major advances in solar power generation technology that allows this (plus amazing work on getting the spacecraft instruments to use very little power). Cassini, for example, uses radioisotopes (plutonium) to generate electricity for its instruments to study Saturn.

At this point, we probably won’t hear much more about or from Juno until October 2013 when it swings by us once again. I expect we’ll get some fun new pictures of the Earth when it does. But after that it’ll be three more years of coasting the cold, dark lanes of space before it gets to Jupiter. And once there, I’m hoping it will do as much for our knowledge of our solar system’s largest planet as all the previous missions combined. That’s the way these things tend to go: the more we do, the more we learn, and the more we find we have to learn.

And on a personal note, it’s really nice to be able to say that humanity now has a new spacecraft on its way to Jupiter. It’s been a while.

Image credits: NASA; JPL/NASA

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Phobos passes Jupiter, as seen from Mars!

MORE ABOUT: Juno, Jupiter

Comments (56)

  1. Great news by Jove! :-)

    Well done & congratulations to all the Juno scientists, engineers and workers. :-)

    Thanks to NASA TV for their excellent online coverage too. :-)

  2. Mark

    Watched the launch on NASA TV… boy was that beautiful. And I actually understood much of what they were talking about! Reading the Apollo mission transcripts paid off!

    Galileo was a fine craft, and it had a great run, but all good things must come to an end, and new good things must take their place.

    Tip of the hat to you, Juno. Godspeed.

  3. mastmaker

    Count me among the ignorant, but if it is going past the Mars orbit by mid 2012, why does it need to come back and sling around Earth one more time? Is it the sun’s gravity that’s holding it back from reaching Jupiter during first pass?

    I have similar questions about the recent Mercury mission, which is making multiple passes in order to settle into orbit around Mercury. If it crosses Mercury, comes back near the earth, and returns to Mercury in order to slow down, why can’t it slow down during the first flight to Mercury? After all it just took off from Earth in the first place, isn’t it?

  4. Nentuaby

    Is it going to be doing any “target of opportunity” science on its way out, the way some past missions have done? Or is it too specialized a machine / lacking in TOOs in its path?

  5. Mejilan

    And away she goes! Best of luck to you on your grand journey, lady!

  6. Lorena

    I hope Juno will be as awesome as Cassini 😀 😀

  7. Mark

    Mastmaker, take a look at the link Phil provided where he said “to steal a tiny bit of our energy”.

    The short answer is, it’s a transfer of kinetic energy using a massive moving body (a planet). Because there’s so much energy that can be played with using the gravity assist, less fuel is needed to be on the rocket or the probe. This means a huge savings in weight and a huge savings in cost, but it takes a lot more time.

  8. andy

    About time we went to Jupiter again, the results from Cassini give some indication of what the loss of Galileo’s high-gain antenna cost us. Though from what I understand this mission isn’t going to do much in-depth study of the satellites.

    Would also be nice to see a dedicated Neptune/Triton mission, but in the current economic climate I doubt we’ll see that for a long time.

  9. Josie

    Will it get there in time to film the propagation of the Monoliths? 😀

  10. jiuguizi

    Nothing about the godly cargo on Juno? Quite possibly the most important thing it is carrying: http://dvice.com/archives/2011/08/these-lego-mini.php

  11. John

    2015 and 2016 are going to be banner years for deep space exploration, it seems. New Horizons will arrive at Pluto, Dawn will arrive at Ceres, and Juno will arrive at Jupiter.

    I’m sure there are others that slipped my mind, as well.

  12. Ted

    Apparently Jupiter kindly hoovers up some of the rocks and stuff that might otherwise have hit us so it is nice that we are visiting and I hope we are taking cake.
    Big leap now to a science question that I have been puzzling over and nobody I know knows the answer but maybe some of you guys do. If a big enough meteor got past Big J and wiped out all life one earth and then after a billion years life took root again and evolved to intelligent life… would the new earthlings know that we were here before them?

  13. Chief

    Isn’t this a great decade for the study of planets.

    Mercury, Venus, Earth, (Moon), Mars, Jupiter, Saturn and Pluto. As well as the pursuit of bodies around other stars. In the immortal words of Phil, WOOT.

  14. Eric RoM

    #13: yes, they would, _once_ they got to the moon. (Love that type of q!)

  15. jaranath

    Ted: I agree with Eric RoM about the moon. Barring that, I dunno. If the asteroid wasn’t so ginormous as to resurface the planet like Venus (or would that even be possible here), I would think they’d be able to detect fossil traces well enough. Not only might they spot our bones and (wrecked) constructs, they’d spot the influence we’d had on the planet, like the extinctions we caused, the shift in species populations and distributions, the rapid changes in chemistry. We would look like a cataclysm in the fossil record even without an asteroid wiping us out.

    Note I’m not even necessarily saying that as an environmentalist lecture (though I am one); it’s just not possible to have a species like us evolve, in the way that we did, that doesn’t have some massive impacts on the environment and ecosystem. That impact would be a beacon to future scientists.

  16. Aarrgh! Robots are winning the space race! Something must be done.

  17. Dr. Morbius

    This mission does not excite me. Spending $1 billion to explore Jupiter but not its moon’s sounds like a wasted opportunity. This mission should have included a lander to Europa or Io. The possibility of life on Europa sounds far more interesting than the structure or chemical composition of Jupiter.

  18. Mike H

    Question regarding the use of solar panels for energy… obviously they need to have a large surface area exposed to catch as much light as possible. But doesn’t that also increase the chance of damage (catastrophic or not) from micrometeroites and the like?

  19. Robin

    @ Dr. Morbius (#17):

    An additional component, like a lander, would have required a lot more fuel (i.e. a lot more money), and likely finer and more course corrections (i.e. more money). As history has shown, there isn’t an unlimited amount of money to be spent on these missions.

  20. Josie

    @10 Jiuguizi:

    THAT is the coolest thing ever in the history of my favorite childhood toys. You just made my Friday afternoon.

  21. Robin

    @ Mike H (#18),

    Technically you are correct; however, given the “emptiness” of space, the odds of such damage is exceedingly low.

  22. Pete Jackson

    @3 mastmaker: It’s a matter of energy. After leaving Earth, Juno will have enough energy to get past Mars’ orbit, but not enough to get to Jupiter. When it flies past the Earth in 2013, it will pick up enough additional energy to reach Jupiter. Note that the heliocentric orbit energy is constant until a near encounter with a planet occurs. Same with orbiting Mercury; in this case, heliocentric energy needed to be dumped on each pass by the Earth, Venus, or Mercury. Only so much energy can be dumped on a given pass. Finally, the heliocentric energy became low enough that the spacecraft could orbit Mercury using its own thrusters.

  23. @ Dr. Morbius (#17):

    A lander on Europa?! Don’t you remember that message we got last year:


  24. Pete Jackson

    I was having difficulty understanding from the popular press and the NASA website what the actual orbits around Jupiter are going to look like. But the following footage from Youtube is excellent, showing animation for the entire mission, both cruise and orbits:


    The perijove of the polar orbit is going to be around +15 degrees north latitude, so that the spacecraft passes over Jupiter’s north pole at a lower altitude than over the south pole. Presumably this choice minimizes the radiation exposure. Perhaps any Juno experts out there can explain.

    Some interesting polar views of the Galilean satellites should be available if the Juno-cam will be able to point at them.

  25. Don´t Panic

    “It’s equipped with microwave”

    Ah yes. The microwaveoven for three entrepid travellers on board!

    But, darn, a 5 year wait…

  26. Egad

    > Juno will take 5 years to get to Jupiter,

    I join with everyone else (+-) in applauding the Juno mission. NASA’s robotic spacecraft have advanced our knowledge of the universe immensely already and continue to do so.

    However, the fact that it takes 5 years to get to Jupiter, and that by sucking energy and momentum by planetary fly-byes, does remind us that our spaceflight technologies are really, really marginal. It would have been nice if NASA had been able to embark on some R&D programs to develop better in-space propulsion technologies rather than ordered to develop a Big Rocket, aka SLS.

  27. Grimbold

    When and if we start doing more outer solar system missions, Jupiter will get more than its fair share of flybys because it’ll be used for gravity assists.

  28. Nick

    It’s a good thing the protective cover on the front of the rocket opened up this time… Didn’t we loose a mission a couple months ago to that? The smog detector mission?

  29. Robin

    @Egad (#26):

    A lot of work has been going on researching propulsion in space. Just look up VASIMR to see what the state of the art is. It’s not that space flight technologies are marginal, but rather it’s that it takes a long time to develop new propulsion technologies. Even with those new technologies, Jupiter is still far away, and energy consumption vs. resources will always be the big constraint in space travel.

  30. lqd

    It’s terrific that we’ve got another probe off toward Jove, but I’m wondering why it will only orbit for a year. Galileo orbited for eight. And the solar panels will most likely impede some of the Juno’s operations, since it will always have to be in view of the sun. I would have loved to have seen some awesome photos of lightning flashing on Jupiter’s night side. Still, I’m excited for those hi-res images Galileo wasn’t able to send!

    @ Dr. Morbius
    NASA and the ESA were going to work together to send probes to Jupiter’s moons in the 2020s, but it doesn’t look like NASA will be involved thanks to the budget mess. According to wiki, the ESA is considering carrying on without the US, and Japan and Russia want to join in.


  31. Speaking of “Earth year”…

    I know a single rotational period of Mars (a Martian “day”) is called a sol.

    What’s a single rotational period of Jupiter called?

  32. Grand Lunar

    Watched online on NASA TV.
    Worried about the delay, so I was glad that it made it up.

    Once again, Atlas 5 proved itself! Go Atlas!

    Wow, 2016 until we get to see Jupiter up close and personel again.
    Still, good things are worth waiting for!

    @31. tracer,
    “What’s a single rotational period of Jupiter called?”

    A Jovian sol?

  33. Ted

    Thanks Eric RoM + jaranath.
    Reading your replies I see that we would leave enough traces from a K2 ish level impact but technically a much more extensive meteor might resurface us to such an extent that effectively nothing would remain. Which is where our friend the Moon chips in. I like the Moon point which I had not considered and agree it gives our detectability a good bit of insurance. They are in for a surprise eh. Watching their first earth rise only to find a golf buggy :)

  34. Gary Ansorge

    33. Ted

    Unfortunately, it took 3.7 billion years to evolve complex life on earth, so a total extinction event would likely NOT allow enough time for such “new” life to evolve, plus there is the problem of solar aging to take into account. Our sun is currently about 40 % hotter today than it was 4 billion years ago. In another one billion years, it will be too hot for life on earth to survive.

    I prefer the alien scientist scenario and yes, the moon might have enough “residue” to tell our story, unless said extinction event also plastered the lunar surface with impact craters from material blown off by the impact with earth.

    On the other hand, some of our outer planet probes might still exist,,,

    Gary 7

  35. Why only one year? They should leave it in orbit of Jupiter taking pictures for as long as it continues to work, instead destroying it after a year.

  36. Robin

    @ Skepgineer (#35),

    One year is the planned mission duration. It is the time over which they expect to have nominal operations. As has been evidenced by other orbiters and landers, missions are quite often extended. The Mars rovers (Opportunity and Spirit) had planned mission durations of 90 Martian days, and look how their missions were extended.

  37. Joseph G

    I really, really hope NASA made decision to use solar panels instead of RTGs purely on the basis of cost and functionality, and not because of the idiot “OMG NOOCLYEEARS ARE TEH EBILZ” crowd. I still remember the hysterical bitching when Cassini went up. I actually heard someone say, without a trace of irony, that the “Satanic” Freemasons in the government were going to crash Cassini into Jupiter, using the Plutonium on board to turn Jupiter into a new star, ala Clarke’s 2010.
    They’re out there, moving around all around us. There’s probably one standing in line with you at the grocery store.
    Morons, I mean – not Freemasons.

  38. Joseph G

    Sorry, this is really great news. I’m just a little cranky right now because a sizable minority in my town is going absolutely bat**** over the new smart meters that the power company is putting in. And not about privacy or accountability or anything reasonable like that, no, it’s an evil corporate plot to cook our brains with microwaves.
    It’s getting really serious – a bunch of them got together and tried to have the Sherrif thrown out of office, because apparently he’s wasting time having deputies deal with actual crime, rather then showing up at peoples’ houses who are upset about smart meters being installed.
    These are the same people who pride themselves on being so much more rational and sophisticated then those ignorant bible-thumping rednecks in flyover country (I live on the west coast). Sigh.
    I know, I know, I need to shut up and start my own blog.

  39. Andrew

    Why did they choose solar panels instead of plutonium to power the spacecraft? Was it to avoid anti-nuke protests?

  40. andy

    Regarding the choice of solar panels over plutonium, I seem to recall a few years back that there was a shortage of plutonium-238 because people have stopped producing it. Blame the “idiots” who ended the Cold War. Google “nasa plutonium shortage” there’s lots of articles on this.

  41. Joseph G

    @andy: Yeah, I answered my own question with the Google.
    Apparently NASA is saving the RTGs they have for missions that absolutely need them (a Europa probe, mayhaps? We can hope).
    I don’t think the cold war has anything to do with it – even during the most Strangelovian hours of the cold war, Plutonium wasn’t exactly something you could buy by the pallet at the hardware store 😛

  42. vince charles

    Please stop posting misinformation that you “seem to recall”, andy. The plutonium isotope used for RTGs is not the isotope that goes “boom.” It must be explicitly created for radioactive heat sources, and has little to do with the military- aside from the military owning the advanced reactors, of course.

    RTGs are a real hassle to deal with, and any mission that can avoid them will do so. For example, once integrated, a radioactive heat source cannot be turned off. The MSL rover needs multiple, redundant cooling systems to ensure it doesn’t cook itself in its shell.

    On a more basic level, RTGs actually hurt the data coming back from a mission. Only a fraction of the output is captured, and just a fraction of that turned to electricity. The stray particles not converted to heat may strike a detector, processor, or memory chip, literally altering their data. This is a real concern for New Horizons.

    Then there’s the paperwork. NASA actually “buys” RTGs from the Department of Energy, which might be a bit easier than setting up a redundant NASA Office of RTGs. “Buys” is in quotes, because it’s not like they’re dropped off, shrink-wrapped, on the front steps. DoE staff are following each RTG for years, through integration, test, and launch. Again, this is because RTGs are not black boxes that can sit quietly, un-maintained, when they are not actually needed for electricity. All this maintenance and inter-agency staffing really impacts our quest toward “plug and play” spacecraft.

    Juno is the latest mission proposal to attempt PV power at Jupiter, actually. Multiple teams had designed post-Galileo spacecraft without RTGs, because it’s just easier for everyone. In particular, the experience of NEAR’s solar panels at 2 AU gave people a lot more confidence- hence, Dawn and Rosetta. Given the impact of a mission failure on careers and budgets, everyone wants to be the second to try a new approach. I’m pretty sure the Juno team was quite relieved when Rosetta’s arrays worked just fine at <3 AU.

  43. andy

    Please stop accusing people of “misinformation” campaigns unless you have good evidence that they have malicious intent, vince charles. I note that while I at least couched my terms uncertainly and directed people to Google you haven’t even bothered to provide a single reference for ANY of your claims.

    And hey just in case you need a bit of help with reading comprehension which it would seem is not your strong point, where did I say this was the isotope that goes boom? According to the references on the Wikipedia article for plutonium-238, it is stated that this was a byproduct of Cold War activities. “Byproduct” being the operative word here.

  44. Daniel

    I’ve looked on the mission website but couldn’t find anything. Does anyone know how close the earth flyby in 2013 will be? And more interestingly will there be any chance we will be able to see it shooting across the sky?

  45. DennyMo

    The family got to see Juno on the pad during our tour of KSC last week, then we watched it lift off before we left the relative cool of Space Coast for the overbaked midwest. So happy we got to see another launch, mildly bummed it wasn’t the shuttle. Pad 39A has already been “wiped clean”, the superstructure for the shuttle launches is gone, making way for other launches. All the videos featuring happy shuttle program employees describing what they do the support the flights, “I’ve been doing this for 26 years” and now you’re unemployed. Yeah, change happens, and manned space launches will happen at KSC again, but my disappointment at the end of the shuttle program is still fresh.

    I was jazzed by all the questions my boys had about Juno, Jupiter, gravity slingshots, maneuvering thrusters, and solar panels. So excitement about space travel and science isn’t necessarily going to die without the shuttle. Old nostalgics like me will just have to get over it. Next!

  46. vince charles

    My references, andy? I bumped into a Juno mission manager in the building, and asked him directly. Did his team mess themselves, when told he would be taking solar panels to >5 AU? He said no, everyone was glad they didn’t have to deal with an RTG…

    Great guy, you could tell he was proud and full of anticipation. He can even demonstrate at least some experience in most of the bands covered by Juno, which I suppose is why he’s a mission manager. Yeah, I know anecdotal evidence is weak evidence. I suppose I should’ve posted a Wikipedia link instead?

    Oh, then there’s the spacecraft power sources I’ve had to deal with. Guess those are anecdotal too, better not say anything.

  47. andy

    vince charles: I have no idea why you so want to paint me as running a misinformation campaign. Guess you are just an ass.

  48. andy

    Furthermore where did I say solar panels would be a terrible choice? I was just suggesting that the plutonium shortage might have factored into the decision. Furthermore I never claimed anything about the relative merits of solar panels. Are you paranoid or something, or are you just unable to read words that are actually there and instead go off with the voices in your head?

  49. vince charles

    You never said solar panels would be a terrible choice- I had asked the Juno guy that last year, when I bumped into him. I never said you said that; what was that about an ability to read words?

    (The question was based on my experience with solar arrays, and the basics of the Jupiter environ… and, again, the preference of missions to be the _second_ to fly any new design or technique.)

  50. DennyMo

    APOD has a good video of the launch posted. One thing the video doesn’t capture is just how bright the flame tip was on the rocket. Almost painful to look at. I expect that has to do with the metallic composition of the SRBs?

  51. andy

    vince charles: then why did you go off on a rant about “Did his team mess themselves, when told he would be taking solar panels to >5 AU?” – as I said I never slagged off solar.

  52. Nigel Depledge

    @ Vince Charles –

    Maybe Andy objected to this line:

    Vince Charles (42) said:

    Please stop posting misinformation that you “seem to recall”, andy. The plutonium isotope used for RTGs is not the isotope that goes “boom.”

    Whaddya think? Any chance you could apologise to him so we can all move on, huh?

    BTW, until I read all this stuff about RTGs, I would simply have assumed that RTGs were better than solar at 5 AU, so thanks for clearing all that up.

    On vaguely the same topic, didn’t each Voyager probe have quite a long boom so the RTGs would neither overheat the spacecraft nor mess up its data? I vaguely recall being under the impression that this was standard practice for using RTGs, so maybe Cassini (which I don’t think has a long boom for its RTGs) is the exception.

  53. Björn

    Magnificent launch it was (albeit somewhat delayed)! This bird went up _fast_! The wonders of the internet can show you how fast exactly by comparing it to an earlier launch of an X-37B: http://youtubedoubler.com/?video1=EIyt5EBUlfM&start1=3&video2=AdCpuv9RCwE&start2=25&authorName=Atlas+V+launch+comparison

  54. Björn

    @Nick (#28): you mean Glory? That was a whole different type of launcher (Taurus, not Atlas 5): http://www.nasaspaceflight.com/2011/03/live-orbital-taurus-glory-with-nasa-satellite/

  55. Jupiter is about 5 AU:s from the sun. I have been publishing lately new astronomical maths fro NASA Sciences. You can find my articles on google by the search word: “antti johannes vaalama and gravity”, please read my articles. I was accepted in 2010 as a researcher at NASA Sponsored Resarch Office, SRO and I am a member of Astronaut Scholarship Foundation. I have new theories about the distances of stars, galaxies etc. and I claim that the nearest stars are in the distance of 80 to 100 AU:s from sun. I claim that gravity is a real time phenomena in cosmos and as we know light is history. So, we live in the universe, universes of Isaac Newton of absolute real time of gravity. Albert Einstein has only explained the theories about light and his theories about relativity is absolutely a right theory but he could not explain what gravity means and how it exists in cosmos.


    Antti Johannes Vaalama
    the city of Heinola, Finland

    Engineer, Violinist, Musician
    NASA Researcher at Sponsored Reseach Office
    A member of Astronaut Scholarship Foundation

  56. m

    I thought gravity exists because of the curvature of space-time from massive objects?

    I’m pretty sure Discover had an article about that.

    But that was before my vacation and my 3 week “brain dump”? :) I might have read it elsewhere.

    If only i could remember my password to my computer.


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