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Juno how to adjust a broken Jupiter probe's orbit?

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I love how often redundant systems on spacecraft end up being used, and how often the whole thing seems to hang on a Heath Robinson bodge.

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But it is also because of all the redundant systems that when something does go wrong they are generally able to salvage the entire thing and still collect massive amounts of new data and extend the life of the mission by 20 or so years.

Top notch job just getting it into any orbit, well done NASA bods.

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Add "and one or two steely eyed missile men"*

*Reference the Apollo 13

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"...missile men"

Or women.

I just attended a fantastic presentation on Juno last night at Purdue University, by a young woman alumnus, now a JPL engineer on the flight dynamics team for Juno. I had many of the same questions you do, and learned some interesting things!

Regarding the burn to go from the 53 day capture orbit to a 14 day "science orbit," indeed it didn't happen yet, because of concerns with a check valve not operating as quickly as it should (minutes not seconds). They're still studying it. The current orbit is a good one, just a bit slow. They might do a lower power (lower ISP) burn at some point and put it into a 21 day science orbit using the engine in "blowdown" mode, where they don't pressurize the propellant tanks, and sidestep the check valve issue. But that's just one option they're apparently considering.

Jupiter, as you probably know, has a daily rotation of about 10 hours and has a pretty pronounced oblateness...so there is a substantial "J2" term in the gravity model of the planet; it can't be treated as a point mass at all times. So during the close-to-Jupiter, perijove part of the orbit, the J2 effect changes the orientation of the orbit. This is well known to those who follow this mission, and was planned for. What it means, is perijove, currently closer to the equator, will gradually move toward the north pole after several orbits, and the high point (apojove) will move further and further south. Why does this matter? The orbit was planned to avoid the intense radiation fields surrounding Jupiter like a doughnut. But due to this orbit shifting effect, eventually the probe will be flying (during part of its orbit) through some pretty intense radiation, off its original path that minimized radiation dose. So toward end of life, she said Juno will have had something like the equivalent of 100 million dental x-rays.

They always plan any orbit changes (burns) to occur when the icy moons (Europa etc.) are as far away from potential harm as possible. Apparently they're obeying the Monolith. They also plan to de-orbit, at end of life, into Jupiter itself, which is apparently relatively OK. (Although my wife points out, we're now contaminating Jupiter with Earth microbes, but maybe they're not expected to survive.) One option they've considered for EOL is to maximize science near the end: lower perijove to skim very close to the north pole, maybe a few hundred km. Then as the orbit naturally shifts perijove to be more and more south, eventually the probe, even if uncontrolled at this point due to electronics failure or lack of fuel, will eventually hit that equatorial bulge around Jupiter and deorbit. That's pretty good flying.

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> Juno how to adjust a broken Jupiter probe's orbit?

Maybe put it near Uranus?

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Fry: Oh, man, this is great! Hey, as long as you don't make me smell Uranus.

Leela: I don't get it.

Farnsworth: I'm sorry, Fry, but astronomers renamed Uranus in 2620 to end that stupid joke once and for all..

Fry: Oh. What's it called now?

Farnsworth: Urectum.

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Alien

Gravity well.

To get the most bang for your buck out of the rocket fuel, course corrections need to be carried out when the spacecraft is nearest the planet, perijove in this case, when it's going at its fastest. So, you only get one chance per orbit. As they missed the first go round, that's about 40 days behind schedule, and the delays now add up for each orbit compared to the original plan.

https://en.wikipedia.org/wiki/Oberth_effect

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Re: Gravity well.

In this case they need to lower the perijove, which can't (to my knowledge) actually be done AT perijove. The most efficient way to adjust the perijve would be a burn at apojove.

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Re: Gravity well.

They are currently in a highly elliptical orbit IIRC...

So they want to lower Apojove, which is best done from perijove (as any KSP player will tell you).

But the 53 day orbit does rather limit the number of attempts they get.

Anyone would think this was rocket science...

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Re: Gravity well.

cheapest course corrections are en-route. everything gets expensive when you are in the sibling gravity well. And KSP players would gravity assist off tylo or laythe (time warping inbetween).

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Re: Gravity well.

It's astounding, Time is fleeting, Madness takes its toll...

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As a newcomer to kerbal space program I feel their pain of not having enough burn for the dV required....

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This post has been deleted by its author

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Alien

Re: Minimising delta-V - The kids are using bi-elliptic transfers...

... and are now messing it up!

Has Jupiter's radiation fried Juno's chips or have the Dwellers deployed Probe Deflection System # 1 (deniable)?

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Re: Minimising delta-V - The kids are using bi-elliptic transfers...

What did you expect with all those spoiled brats used to MechJeb and manouvering nodes. Back in my day when we wanted to transfer to Laythe we had to guestimate a burn and go for it.

--> The one with the StrutCo. logo on the back please.

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Re: Minimising delta-V - The kids are using bi-elliptic transfers...

+1 for the IMB reference...

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Bit of a drag

Juptier next at perihelion in Jan 2023 - bit of a wait for some higher flying atmosphere. Can the current spacecraft change aspect/shape a bit and increase what little drag* it is currently experiencing? Every little helps as Tesco says.

*Okay, so say it is 10 times higher than we normally worry about drag - I am still willing to bet there is more than none. Anyone got a licensed copy of STK?

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Use the gravity of a moon to assist / resist?

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