Juno perijoves 2 and 3, October 19 and December 11, 2016 |
Juno perijoves 2 and 3, October 19 and December 11, 2016 |
Oct 26 2016, 04:44 PM
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#1
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Junior Member Group: Members Posts: 23 Joined: 13-October 13 Member No.: 7013 |
A lot has happened and it seemed like a good time to start a new post. We will be staying in 53 day orbits until the project has a full understanding of the risks that may or may not be associated with reducing the orbit period to 14 days per our previous plan.
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Dec 18 2016, 06:32 PM
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#2
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
I was just looking for a simple solution to adjust for possible relativistic effects regarding spacecraft rotation. Since Juno's trajectory isn't an inertial system, but accelerated in a Newtonian understanding, we get into GR. I'd think, that this is implicite in SPICE by Ephemeris time (ET) - UT transformations.
I've been considering, that Juno's time-dilated rotation by GR might be equivalent to an offset by light travel time. But discussing this -- as M.Caplinger says -- would be an extra thread. Since I can't be sure yet, to which degree relativistic effects play a role, and how complicated those considerations might become, I decided to adjust rotational offsets manually in a first step. Edit: After these adjustments, the fitting looks better: Maybe worth to create an animation (video) with black background and interpolated frames. |
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Dec 18 2016, 07:14 PM
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#3
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Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
I'd think, that this is [implicit] in SPICE by Ephemeris time (ET) - UT transformations. I don't think so. If this was the case then all time conversions would require knowledge of position. I think the full extent of SPICE's treatment of GR is in the mapping from ET=TDB to TDT, which applies only to the Earth and is not something I've ever used. See https://naif.jpl.nasa.gov/pub/naif/toolkit_...ound%20Material I'd guess, without having worked it out, that in the total error budget of spacecraft pointing, GR effects are several orders of magnitude down in the list, at least for spacecraft and targets like the ones we deal with now. In the future, if mission planners are flying relativistic spacecraft to black holes, the SPICE toolkit will have to be enhanced. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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