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Juno at Jupiter, mission events as they unfold
Tom Tamlyn
post Mar 3 2017, 03:47 AM
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There are a dozen or more Juno abstracts attached to the program for the Juno sessions at the April EGU ("European Geosciences Union General Assembly") that Gerald linked to just upthread. However, none that I saw is longer than a page, some are only a few sentences, and some really don't contain any substance at all with respect to results.

None of this is surprising. As JRehling (and others) have noted, "Juno will not lend itself well to frequent science updates." There are plenty of good reasons not to release very preliminary figures on paper.

However, I noticed that the abstract for the JunoCam discussion had more meat to it than many of the others. I was also pleased to discover that the "professional" scientists have included Gerald as one of the JunoCam abstract's authors as an "independent scholar." It's fitting recognition for the amount of work and skill he has invested in working with JunoCam images.
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Gerald
post Mar 3 2017, 02:08 PM
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Thanks! I appreciate very much the allowance to collaborate with the Juno team, and the honor to be mentioned as a co-author. smile.gif
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tanjent
post Mar 30 2017, 03:57 AM
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At some point in the mission, after n successful orbital passes, and with enough science data already in the bag, Juno's management team will become less risk-averse and begin to consider taking a chance on re-lighting the main engine. The most obvious choice would simply be to make a delayed shift to 14-day orbits, as originally planned. But those unexpended resources might conceivably be used in other ways too. If the orbital science program were to be completed in the 54-day orbit configuration, what other innovative mission extensions could be considered? For instance, I'm wondering if it would be possible to approach Io or one of the small inner moons without being overcome by radiation. Or, since the probe is designed mainly for deep examination of the planet itself, could the orbit be adjusted to perform one or more close approaches over a pole or over the red spot, again without frying all the instruments?
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mcaplinger
post Mar 30 2017, 04:15 AM
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QUOTE (tanjent @ Mar 29 2017, 07:57 PM) *
At some point in the mission... Juno's management team will become less risk-averse and begin to consider taking a chance on re-lighting the main engine.

Not in the plan. https://www.nasa.gov/press-release/nasa-s-j...rbit-at-jupiter -- "NASA’s Juno mission to Jupiter, which has been in orbit around the gas giant since July 4, 2016, will remain in its current 53-day orbit for the remainder of the mission." (italics mine.)

Reducing the period simply shortens mission duration, it doesn't really change what science can be done.

The instrument suite is simply not capable of doing any substantive science of the moons, and the orbit is just fine as is for doing everything it can do. And I don't think the amount of remaining delta-v (about 350 m/s) is all that enabling of major orbit changes other than period reduction anyway. But feel free to peruse "Minimum impulse transfers to rotate the line of apsides" and report back -- https://trs.jpl.nasa.gov/handle/2014/37665 -- IIRC the rule of thumb is that the delta V of a apsides rotation is 1/4 of the velocity difference at the point where the old and new orbits cross.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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propguy
post Sep 30 2019, 03:05 PM
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Just a short mission update. Today Juno does it longest burn to date in orbit (the so called Apojove 22 maneuver). We do an Apojove maneuver most orbits to tweak the Perijove timing and aim point, but this one is quite large to avoid an eclipse of Jupiter. When we entered Jupiter orbit we essentially were at a right angle to the orbit (i.e if Jupiter were at midnight relative to the sun in the orbit Juno is orbiting around Jupiter in a circle around the axis from the sun to Jupiter, passing over the poles to stay in the sun at all times). This is critical in that we never want to go behind Jupiter (very important for a solar powered vehicle). Now that we are 3 plus years from JOI Jupiter has moved 90 degrees in its orbit and will eclipse Juno if no burn is done (~18 hr eclipse, no way to survive that). Thus we are doing a 11 hr burn today on the monoprop thrusters (would have been minutes on the main engine, but that is not an option for use now). No real risk of issues juts a very long day (and night) of operations. It is not a critical single chance burn like JOI was (since we have a secondary and even a tertiary burn planned if needed) but the maneuver itself is critical to proceeding to Perijove 23. For those that really study Juno's orbit yes, we are not at Apojove yet. Doing the burn a little early leaves us less propellant penalty for the later options v.s doing the primary burn right at Apojove. Should be a interesting (but long and boring)evening and night as we watch this occur. Sorry there is not NASA TV feed of this like there was for JOI (would be quite boring actually watching the Doppler plot slowly grow to show progress). I will not be allowed to keep a running status since we in ops are not allowed to provide public status but look for a press release soon on the results.

Very interesting that this eclipse avoidance comes just after the Io eclipse of Jupiter, but it makes sense in that we are in a point of the orbit to view that angle of Io on Jupiter relative to the sun. Go Juno!
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nprev
post Sep 30 2019, 08:27 PM
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Thanks for another fascinating and informative insider's look, Propguy! smile.gif Best of luck with the burn, and looking forward to a happy press release.


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A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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propguy
post Oct 1 2019, 02:09 PM
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Can't provide specifics but it was a good and uneventful night. Go Juno, ready for Perijove 23.
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Kevin Gill
post Oct 1 2019, 08:16 PM
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Thank you propguy. Is there an updated schedule of upcoming perijoves?
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propguy
post Oct 2 2019, 03:33 AM
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QUOTE (Kevin Gill @ Oct 1 2019, 01:16 PM) *
Thank you propguy. Is there an updated schedule of upcoming perijoves?

The best website I have seen has some charts provided by JPL that are the same (but slightly dated versions) of what we are working to. The eclipse avoidance maneuver did not change our orbital period, it is still the roughly 53 day period, thus the dates do not change off these charts. Of course the exact timing can vary if they chose a different longitude of passing (if we slow down or speed up in the orbit we can target a wide range of different longitude at Perijove since Jupiter has such a high spin rate).

https://www.britastro.org/node/16177
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