MGS in Trouble, Formerly: MGS in safe mode |
MGS in Trouble, Formerly: MGS in safe mode |
Guest_Analyst_* |
Nov 8 2006, 11:50 AM
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#1
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Guests |
Did nobody notice this:
Ground Team Stays Busy on 10th Anniversary of NASA Mars Launch Ten year after launch, there is some trouble with a solar array motor and a comm problem probably resulting from this and entering safe mode. Nothing dramatic yet, but something to follow closely. There are other things than MRO and MER Analyst |
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Nov 15 2006, 10:25 AM
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#2
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
When I started this place a couple of years back - I never thought I'd see a debate between MOC/CTX and HiRISE people over the relative difficulty of photographing spacecraft - what a very very sureal thing to read over ones cornflakes
Doug |
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Nov 15 2006, 10:44 AM
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#3
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
A very back-of-the envelope calculation, could be very wrong, but still I think it's illustrative:
Assuming a 118 minute orbit, 3800 km orbital radius, 3.37 km/s orbital velocity here. That amounts to 122 orbits in 10 days. Let's suppose we change the orbital radius by just 100 meters, from 3800 km to 3800.1. Given the ratio of orbital periods T1/T2=SQRT(R1^3/R2^3), that gives me around 0.9999605 T ratio. Multiply (1- 0.9999605) by 118 minutes, that amounts to a difference of about 0.28 seconds per orbit. Now, 122 * 0.28 s * 3.37 km/s = 115 kilometers in along-track drift. Not exactly peanuts. It's not getting any smaller as time passes, either. Note how even a small, 100 meter radial change in orbit radius results in an 3 orders of magnitude larger change in along-track position. -------------------- |
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Nov 15 2006, 07:45 PM
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#4
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Member Group: Members Posts: 688 Joined: 20-April 05 From: Sweden Member No.: 273 |
Now, 122 * 0.28 s * 3.37 km/s = 115 kilometers in along-track drift. Not exactly peanuts. It's not getting any smaller as time passes, either. Note how even a small, 100 meter radial change in orbit radius results in an 3 orders of magnitude larger change in along-track position. 122*0,28 = 34 seconds. So what you do is start taking pictures say 30 seconds before the nominal expected arrival time at the aimpoint and keep it up for one minute. The interval depends on the cycle time of the camera and the FOV since the interval must be shorter than the time MGS will need to cross the FOV. MGS should show up in at least one image and once you have pinned down the current orbit it should be possible to find it again at higher magnification. tty |
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