Rover Orientation Data, Where can one find detailed rover orientation data? |
Rover Orientation Data, Where can one find detailed rover orientation data? |
May 28 2011, 04:20 AM
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Senior Member Group: Members Posts: 2228 Joined: 1-December 04 From: Marble Falls, Texas, USA Member No.: 116 |
I am trying to quantify Spirit's final resting orientation, but I would generally like to learn how to determine the orientation of either rover for any particular sol. I'm sure this data is in the MMB files somewhere, but I haven't been able to identify it. Likewise, I am sure it is somewhere in the Analyst's Notebook database and/or the Pancam data tracking database, but again, I can't find it.
Spirit's final orientation is the main thing I am looking for, but any orientation assistance would be greatly appreciated. Thanks. -------------------- ...Tom
I'm not a Space Fan, I'm a Space Exploration Enthusiast. |
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May 30 2011, 01:06 PM
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Tom, my experience with inertial nav systems is almost entirely aircraft-related, so within that context the difference between local vertical & the geoid is significant enough to be considered, esp. during initial system alignment on Earth. (Choice of the reference geoid is also important; there are several in current use.) I don't know how refined such data is for Mars yet.
As you pointed out, though that might not matter for the MER INS. All that stuff matters for initial platform alignment on a planetary surface, which works basically like this for aircraft inertial systems: 1. Platform levels out orthogonal to local vertical. 2. Amount & direction of correction required to keep platform level over time (normally, a few minutes) is measured. 3. Correction rate is matched to expected drift rate to find latitude; correction direction used to find north. (Finding exact longitude is usually done by entering an appoximate longitude during the alignment process, which is subsequently refined by the system; there's no real easy way for the system to sense that independently.) I suspect that the MERs haven't been going through full daily alignments for all this time; after morning wake-up, they might well just spin up to the last stored coordinates. Over time, this will drift (normally at a fixed rate) due to inherent & unavoidable minor mechanical imperfections in the system. Therefore, I wonder if this raw data you're working with might have substantial cumulative errors included that are subtracted during groundside processing @ JPL. Anyhow. Sorry for the long stream-of-consciousness post; was trying to think this through. Good luck! -------------------- 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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