A NASA Scientist Answers Questions About the Juno Mission to Jupiter

By Jennifer Ouellette on at

NASA’s Juno spacecraft entered Jupiter’s orbit last night after a very long journey, kicking off the next phase of its mission. NASA JPL scientist Glenn Orton has been kind enough to answer some burning questions about Jupiter, the Juno mission, what the team hopes to learn about our solar system, and more.

What is the space time differential between us and the craft? How much will it change over time?

GO: It’s about 48 minutes. It won’t change much over time – just a few minutes; it depends solely on distance between the Earth and Jupiter, ranging from 4.2 to 6.2 Astronomical Units (AU) (One AU is the distance of the Earth from the sun)

Juno Cam almost seems like an afterthought on this spacecraft. I know that the primary focus of this mission is the other instruments, but it seems crazy to send something all the way to Jupiter and not put the most awesome camera you can on it. Can you explain the rationale behind the decision to use such an under powered imaging system here?

GO: The focus of the mission is on the interior, parts of the planet we’ve never seen before. We on the science team also thought it was a shame to sent a spacecraft to Jupiter without a camera. So we thought getting a less expensive camera on board, so we wouldn’t pass the cost cap for the New Horizons series of missions, but making it commandable by the public would be the best compromise. So you’ll soon get to vote on just what YOU want to see “close up and personal” on Jupiter.

What’s the most exciting discovery that Juno could make during its close orbit of Jupiter?

Go: The general question is what is the interior structure of Jupiter like, and that’s the main focus. We’ll be peeling back that outer layer of an orange and finally seeing the juicy stuff inside for the first time. But specifics like: how deep does the Great Red Spot and the general banded structure of the planet really go? A big general one driving the mission: what is the abundance of water in the deep atmosphere, something that the Galileo probe gave us strange results on.

Can you break it down in layman’s terms of all the goals for this mission?

GO: What is the interior of Jupiter like? What is the abundance of water (and thus the oxygen-to-hydrogen ratio); is it different from one determined by the Galileo probe, which was unexpectedly low? What’s the structure of the full magnetosphere and how does it vary with time? How does it interact with the solar wind (charged particles emerging from the sun) and create polar auroral glow?

Does the Juno spacecraft have thrusters that can adjust it’s position in Jupiter's orbit?

GO: Yes, we’ll be making tiny changes to the rotation axis of the spacecraft to optimise the MicroWave Radiometer (MWR) instrument sensing.

I’ve always thought of Jupiter as a very weird, magnificent, almost eerie, place thanks to Kubrick’s ‘2001: A Space Odyssey.’ Do any NASA scientists such as yourself share this view, and what is the weirdest thing we’ve learned about Jupiter so far? What other weird facts are you hoping to find out from Juno?

GO: Weird stuff about Jupiter indeed! Kubric’s masterpiece is my favourite movie of all time; is it yours? Weird stuff will be what we don’t know about yet. But really weird will be that the Great Red Spot is just a surface feature. Or really weird is that it lasts as a structure to hundreds of miles deep into the atmosphere. Time will tell!

What are the mission control computers running on? Mac? Pc? Linux?

GO: I honestly don’t know that answer to that question. Sorry.

Will Juno be solely focused on Jupiter or will any of the moons get some attention?

GO: Jupiter is by far 99.99% of the focus, but the JunoCam experiment may be able to get some images of the satellites. But nothing to rival Voyager, Galileo or New Horizons images. We’re just never close enough.

Is it totally impossible to live on Jupiter? Why does it take so long to travel to Jupiter? What kind of data can the Juno spacecraft collect for us?

GO: Yes, unless you like floating and breathing hydrogen. :-) Jupiter is 5.2 times the distance the Earth is from the sun, so it’s just more difficult to reach - requiring a bit of patience on the part of us scientists!

What are your thoughts about a sample return mission to Jupiter? Never going to happen?

GO: It’s hard to sample an atmosphere. The closest we came was the in-situ sampling from the Galileo probe in 1995. We might go deeper, but first we thought it would be easier to scan the planet using microwave remote sensing and gravity mapping first.

How has NASA been able to preconceive the exact path that Juno would be on, when there is no gravity and plenty of magnetic pulses throughout space, not to mention astroids. I mean, other than two thrusts from Juno, how could you mark it’s path so precisely?

GO: There is, in fact, gravity from the sun, and gravity from Jupiter – but both those masses are very well known. There really aren’t many magnetic pulses through space, and – anyway – they don’t affect the gravity that influences the spacecraft trajectory. So we can be so accurate precisely because there are no other major forces acting on the spacecraft and, by now, we have calibrated the engine system so well that the spacecraft response is extremely well known.

What data would indicate that the core is solid? Could you tell what it is made of?

GO: That’s going to be the result of modelling from the gravity mapping. I think we can only place boundaries on it from assumptions about the mean molecular weight of material.

How are you prepared Juno to deal with Jupiter’s harsh radiation. Do you already have a complete picture of the radiation it will face, or is the radiation strength throughout one of the data points you’re looking to collect?

Also, are there plans to use Juno’s data on space radiation to help shield future missions into the solar system — perhaps even one with a human crew?

GO: Terrific question. We’re using the best models we have from all the spacecraft that have visited Jupiter. But nobody’s gotten this close to Jupiter in this particularly harsh part of the magnetosphere, so we’re really going to be working the challenge of the unknown unknowns! Yes, this will be a very important data point that we’ll be collecting twice on each orbit (entry and exit from each perijove).

I hope this work helps future work in general, but all other planetary systems have much wimpier electromagnetic environments. So, if we can “make it there, we can make it anywhere”. :-)

One more question! Will anything learned from Juno feed forward into NASA’s planned mission to Europa?

GO: Certainly anything about the radiation environment and its variability. On a scientific note, the water abundance in Jupiter that can be compared with Europa (if we’re sampling it in some way with the Europa mission), in order to complete models for the formation of the entire system.