Mars 3 (Various Topics Merged) |
Mars 3 (Various Topics Merged) |
Dec 29 2004, 10:36 PM
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
On my website sometime back, I added a page on the image fragment sent back by the Mars-3 Lander. I released serveral versions, including the best quality processing using othodox techniques I would use on other images plus colorization here:
http://pages.preferred.com/%7Etedstryk/fragmentc.jpg However, I released another image, which I called a "What if" image. This image can be seen here http://pages.preferred.com/%7Etedstryk/m3s5b.jpg It was produced via extreme processing of the original data to make a Mars-like scene, but I made it clear on my website it was only a speculative image. I strongly doubt if the raw data even shows Mars at all - it could be all noise. But since this mode of processing looked strangely Viking-like, I figured I would put it on the web. I was warned by several, who said that while fun, some kooks might take it seriously. My response was that I really don't care what kooks think. Then I noticed this web page: http://en.wikipedia.org/wiki/Mars_2 They used the overprocessed image. I feel like it is being presented as a true photograph. This is of concern. -------------------- |
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Guest_BruceMoomaw_* |
Apr 18 2006, 10:18 PM
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Guests |
The Soviets actually do firmly know why Mars 2 failed, as V.G. Perminov said in his interesting historical document "The Difficult Road to Mars". They didn't trust the accuracy of their radio tracking network, so they incorporated an optical guidance system into the Mars 2 and 3 orbiters to allow them to calculate the optimal course for their final pre-arrival midcourse correction. Unfortunately, the Soviets had slightly inaccurate data on Mars' ephermeris, and so -- while Mars 2's onboard system worked as planned -- it ended up putting its lander onto a course directed at too steep an entry angle, which would have led to the lander crashing in any case before its parachute could properly brake it.
The Bad Luck Fairy that has always haunted the Russian Mars program struck in a particularly brutal way that time. First, the next year the US (as part of a planetary science data exchange program) provided the Soviets with a corrected Martian ephemeris -- and, second, it turned out afterwards that if the onboard optical system HADN'T made that correction, Mars 2's preexisting approach trajectory would, by pure luck, have put the lander on a properly shallow entry! The failures of the Mars 3 and 6 landers remain more mysterious. Perminov expresses his suspicion that Mars 3 might perhaps have been knocked out by an electrostatic discharge from the giant dust storm it landed in. As for Mars 6, it failed at about the time its final solid-fueled braking rocket was supposed to fire -- meaning that the rocket could have fired at an inappropriate time due to Martian conditions, failed to fire at all, or exploded. |
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Apr 19 2006, 03:59 PM
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
The Soviets actually do firmly know why Mars 2 failed, as V.G. Perminov said in his interesting historical document "The Difficult Road to Mars". They didn't trust the accuracy of their radio tracking network, so they incorporated an optical guidance system into the Mars 2 and 3 orbiters to allow them to calculate the optimal course for their final pre-arrival midcourse correction. Unfortunately, the Soviets had slightly inaccurate data on Mars' ephermeris, and so -- while Mars 2's onboard system worked as planned -- it ended up putting its lander onto a course directed at too steep an entry angle, which would have led to the lander crashing in any case before its parachute could properly brake it. The Bad Luck Fairy that has always haunted the Russian Mars program struck in a particularly brutal way that time. First, the next year the US (as part of a planetary science data exchange program) provided the Soviets with a corrected Martian ephemeris -- and, second, it turned out afterwards that if the onboard optical system HADN'T made that correction, Mars 2's preexisting approach trajectory would, by pure luck, have put the lander on a properly shallow entry! The failures of the Mars 3 and 6 landers remain more mysterious. Perminov expresses his suspicion that Mars 3 might perhaps have been knocked out by an electrostatic discharge from the giant dust storm it landed in... This is a discussion we should have been having two years ago, right after the MER's descended more rapidly than expected...and it would be helpful if complete engineering Doppler and accelerometer data would be made public so that we can work the problem. Sheeesh. Perminov's speculation that Mars 3 suffered a static incident is just that: He pointed out probes entering the Venician atmosphere snap crackled and popped, but he has no data from Mars to support this guess. We have had two probes scurrying around Mars for two years now without a single mention of a static event, making Perminov’s theory even more suspect. (Spirit and Opportunity didn’t even experience plasma blackouts.) Likewise, blaming the Mars 2 failure on both a bad ephemeris and a bad self-correction is a little like insisting the failures of both Beagle and the Polar Lander were absolutely caused by bad engineering, now that another likely suspect has emerged. There have been a lot of hints something isn’t right in earlier missions: Both Viking craft experienced accelerations that indicate an ‘over performance’ of the parachutes, while the Pathfinder EDL indicated an ‘under performance’ of the same design. I think both characterizations are in error: The Pathfinder did not contain accelerometers, relying on Doppler, while Viking did not have Doppler, but did have accelerometers. If you run the numbers, it is easy to see how in both cases greater acceleration than expected would end up as puzzling drag coefficients. Too many degrees of freedom! More sensors needed! It is no secret my own bias towards an exceptional solution skews my interpretations of these events, but until we have all the facts on the table, it is difficult to judge which of the many possible scenerios have led to so many failures. PhilHorzempa’s correct; a reevaluation is in order, and for heaven’s sake let’s figure out how to properly characterize the atmosphere! |
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Apr 19 2006, 04:20 PM
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
and it would be helpful if complete engineering Doppler and accelerometer data would be made public so that we can work the problem. Sheeesh. Have you actually looked at the data that have been released to assess their adequacy? The pre-entry state of the MERs, which is what people have complained about, are on the NAIF FTP site, I believe. All of the raw data appears to be out there to do whatever EDL reconstruction you want; I don't think that the MR doppler tracking is actually useful for the reconstruction, but I believe it was archived with the MOC PDS releases quite a while back. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Apr 19 2006, 05:56 PM
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
Have you actually looked at the data that have been released to assess their adequacy? Yes and no. I have made inquires, and been told the engineering data is not going to be made publicly available. QUOTE The pre-entry state of the MERs, which is what people have complained about, are on the NAIF FTP site, I believe. All of the raw data appears to be out there to do whatever EDL reconstruction you want; I don't think that the MR doppler tracking is actually useful for the reconstruction, but I believe it was archived with the MOC PDS releases quite a while back. Paul Withers wrote in an MER EDL paper he has submitted to Icarus, that he had to make a lot of approximations concerning initial conditions - perhaps the needed information is available now at the NAIF FTP site...whatever and where ever that is. If it is where I have been looking before, there are a lot of 'expected' tables, but the "reconstructed" or actual descent data is just not there. Paul emailed to me that he thought some of the data is ITAR restricted, but I don't see why. He also said that a well-funded study of the MER EDLs - comparable to earlier missions, is not 'in the budget' - I assumed he meant NASA isn't really taking these things apart, but I have been wrong before. I've been raising my hand and holler'n that I think I can see a stunning trend for a year-and-a-half now. It is hard to get attention when so few people seem to know that the MERs almost splatted - Pathfinder too. As far as I know this is the first really public admission the missions were in jeopardy: QUOTE (ToSeek) At least now I can go to my congressman and tell him why we need to fund more Mars science before we can even dream of going there, because something is not well understood. |
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Apr 19 2006, 06:20 PM
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
Paul Withers wrote in an MER EDL paper he has submitted to Icarus, that he had to make a lot of approximations concerning initial conditions - perhaps the needed information is available now at the NAIF FTP site...whatever and where ever that is. If it is where I have been looking before, there are a lot of 'expected' tables, but the "reconstructed" or actual descent data is just not there. If you're going to make sweeping assertions, it might help to exhibit more cognizance of the process involved. The NAIF FTP site (naif.jpl.nasa.gov) is the standard place where JPL trajectory information is released. The file /pub/naif/MER/kernels/spk/spk_a_c_030610-040104_recon.bsp on that site is, according to its label, "a reconstructed cruise trajectory for MER-A, beginning at TECO and ending at atmospheric entry." There is a similar file for MER-B. If Withers is unaware of those files, you might want to make him aware. If there's something inadequate about the information, I'd be curious as to what. As previously noted, that state information and the EDL engineering telemetry archive, which has been released and is available on the PDS atmospheric node, are all the information I can think of that would be useful for reconstructing the entries of the MERs. I'm no apologist for JPL, but carping on this topic would appear to be unjustified. Now, it may be that what Withers is lacking is a detailed description of the MER aeroshell composition, shape, etc. The design details of reentry vehicles are covered under ITAR for what would seem to be legitimate reasons. I haven't tried to find those details, nor do I know what data precision might be required. There's a fair bit of info in http://library-dspace.larc.nasa.gov/dspace...ndle/2002/11213 -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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