Mars 3 (Various Topics Merged) Options

[tedstryk]

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.

[Phil Stooke]

http://www.laspace.ru/rus/mars23.php

Lavochkin website on Mars 2 and mars 3. Hmmm. This is the source of the Wikipedia location for Mars 2 - 4° north, 47° west, near Nanedi Vallis in Xanthe Terra. (Thanks Maxim for the information).

But this is completely at odds with information published at the time (links I'll have to dig out, but I think Marov & coauthor, Icarus, 1973) (atmospheric entry at 45 south, 313 west, with crash near 45 south 302 west).

I'm not sure where this leaves the problem, but I don't think it is likely that these coordinates can be correct.

Phil

[Geert]

I'm not sure where this leaves the problem, but I don't think it is likely that these coordinates can be correct.

I fully agree with you that they are very (unlikely) far from the planned landing at Hellas.

Perminov ('The difficult road to mars' NP-1999-06-251-HQ) does not mention any crash-location for Mars-2, and in my opinion his booklet is a quite accurate source for Soviet planetary flights in that period. If he does not mention a crash-location it sounds like nobody at the time was quite sure as to where it ended. If there were indeed no communications with the Mars 2/3 landers after release of the orbiter until after landing then how can we be sure its retro rocket actually fired? The lander might have missed Mars completely and ended up in solar orbit...

I'm still trying to work it out, but the landers used a solid propellant retro rocket, causing a 120 m/sec velocity change. They were released at 46000 km from Mars in an orientation almost perpendicular to the fightpath (drawing at page 53 of the Perminov booklet). The lander was spin-stabilised after release and automatically fired its rocket 900 seconds after release, everything completely pre-programmed. As it was released perpendicular to the flightpath, the pulse of the lander engine did not so much 'brake' its speed as well change the vector and reduce the fly-by distance from 1500 km to zero. In this scenario there is actually not so much you can do to 'steepen' the descent, almost any error in orientation will cause the lander to 'miss' Mars altogether and disappear into solar orbit.

So, it sounds like the whole scenario depended on the trajectory of the mothership at the moment of release, and this is probably what went wrong with Mars 2. According to plan (Perminov, page 53 again) the mothership would be in a trajectory with a fly-by distance of 2350 km +- 1000 km prior to its third and final course correction. This course correction was automatically computed by the onboard computer, and should have resulted in a fly-by distance of 1500 km +- 200 km, where after the lander was released. On Mars 2 the mothership was actually in a fly-by trajectory with a fly by distance of aprox 1500 km prior to the third correction, but instead of skipping the third correction, the onboard computer ordered a third correction which actually 'overcompensated' and decreased the fly-by distance too far. (Perminov, page 57). Mars 2 there after ended up in an orbit with a perigee of 1350 km instead of 1500 km.

Thus it sounds like the whole error was in the final trajectory on release of the lander, which was too steep with a too close fly-by distance. Supposing the lander rocket fired correctly (which we can't be sure of!) this would indeed result in a descent which was too steep.

However, the trajectory can't have been too far off, otherwise the mothership would have burned up in the atmosphere, which it didn't. It's all 'back of the envelope' calculations, but let's say Mars 2 was 300 km 'off track' on release of the lander, then the final entry trajectory of the lander must have been 300 km off track as well (impuls of solid rocket was fixed, lander sequence pre-programmed). Given a Mars radius of 3396 km, this would result in an atmospheric entry angle of 90 - ASIN((3396 - 300) / 3396) = 25 degrees, which is obviously too steep.
Presuming the original entry angle was close to zero, error in landing location would in this case also be 25 degrees, or 1481 km. (see attached drawing).



The very, very, worst case scenario (given the mothership did not burn up in the atmosphere, so must have passed let's say minimum 200 km) would put the lander off track by 1300 km perpendicular to its trajectory, which will give an atmospheric entry angle of 52 degrees and an error in landing location of 3081 km. That's absolutely the very worst case scenario, I can't create a bigger error given the fact that the mothership obviously survived...

So 'most likely' error would be in the range of 1481 km maximum and absolutely worst case error would be 3081 km. It looks to me like the lander was targeted for the Hellas bassin (they seem to have targeted for locations imaged by Mariner 4/6/7 so targeted area must be within one of these pictures), so draw an E-W elips with a maximum radius of 1481 km centered on the Hellas location and start searching...

Note this is all 'back of the envelope' calculating, obviously a lot of factors aren't taken into account but it give's the basic idea of what error we are looking for.

Regarding Mars 3 and 6, the Perminov booklet states a maximum allowed error in atmospheric entry error of 5 degrees, if you ignore all other factors, this gives a landing elips with a maximum radius of almost 300 km (any bigger error and they wouldn't have survived entry). It remains a very big area to search...

Regards,

Geert.