ExoMars - Schiaparelli landing |
ExoMars - Schiaparelli landing |
Aug 12 2016, 07:07 PM
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Solar System Cartographer Group: Members Posts: 10170 Joined: 5-April 05 From: Canada Member No.: 227 |
Starting a new topic here - hopefully that's OK! Clearly there will be a lot of action around this in the next weeks and months with descent images and HiRISE views of the hardware.
I thought I had posted this map earlier but apparently not. This shows the various landing ellipses in this area. The original plan was for an ellipse oriented NW-SE, but it changed with the different launch date and is now nearly E-W. Note that the ellipse shown in the recent ESA release is the envelope of all ellipses over a given launch period, but the actual landing ellipse for the given launch date is smaller. Opportunity's final landing ellipse is shown for comparison. http://exploration.esa.int/mars/57445-exom...6-landing-site/ http://exploration.esa.int/mars/57446-exom...6-landing-site/ Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Oct 26 2016, 08:10 AM
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
Those event-triggered multi-threading systems are very hard to test and debug.
There may have been set a timer, which triggers the thruster shut-down if some event hasn't occurred within this time. If, for example the velocitiy variable is initialized with zero, and adjusted by the radar after an assumed time, a delayed setting of the variable may return standstill, although the variable simply hasn't been set. This could be resolved to some degree by adding an invalid flag. But how should the system behave in case of an invalid variable? Default would still be thrusters off, since waiting too long near ground with thrusters on would prevent a landing, and thrusters on during flight would be wrong, too. There are certainly thousands of possible errors of this kind you don't see in a fixed set of simulations. With the actual data, they can now set-up a new series of unit tests to get closer to real conditions near Mars. And once the error is nailed down, some will certainly say, that this could have been known before. But before the real-world test, finding a needle in a haystack is much easier. I'm wondering now, whether another test with a low-cost lander should be performed, or if the expensive payload should be risked without a prior fully accomplished landing test. |
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