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Pictures from Mars 
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Google Mars: detailed interactive surface maps


Wed Mar 31, 2010 7:05 am
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A nice Viking orbiter photo from 1976, with the atmosphere visible; small dust particles in Mars' atmosphere filter out energetic blue light like an Earth sunset, increasing the reddish appearance of the planet:

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image by NASA (source)


Wed Mar 31, 2010 7:24 am
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Martian sunset from the Spirit rover:

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image by NASA (source)


Wed Mar 31, 2010 7:41 am
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Apparently there's a "Mars Curse," namely just that a high percentage of missions to Mars have failed: 19 of 39 Earth-to-Mars missions have failed. NASA's gone 13 for 18, so the percentage for everyone else is actually much more dismal: out of 21 missions by others, only 7 have succeeded.

Wikipedia's Exploration of Mars page has a list of mankind's missions to Mars, and I found three failures in particular that were interesting--two of them by NASA, even!

- Viking 1 Lander (1975)

The Viking 1 lander lasted longer than the other three components of the Viking project (the other lander and their two orbiters), and was still going pretty strong on the Martian surface until software uploaded to it in 1982 overwrote the program in charge of aiming its antenna, causing permanent loss of contact with the lander. Who knows what it's up to now? (Well okay its radioisotope power probably ran out.)

- Phobos 2 (1988)
Quote:
The Phobos probes had three identical computers which controlled them. For every operation, the craft would do what at least two of the three computers would tell it to do. Not long into the mission, the first computer failed. As Phobos 2 approached Mars, a second computer began to falter. Three months after arrival, it failed as well. The one remaining computer could not beat the two votes of the failed computers, and thus could not control the spacecraft, which lost contact with Earth on March 27, 1989.

So funky that they gave it that triumvirate control scheme (and there's the notorious Soviet penchant for redundancy again ;)! I'd like to know more about it, because if the computers were identical, you'd think they would have always given the same responses.

- Mars Climate Orbiter (1998)

This probe burned up in the Martian atmosphere after going too low; the error was due to the thruster control software making calculations that assumed the numbers it was given representing the Imperial system (pounds force), while as far as the hardware configuration went, they were supposed to be metric (newtons)--so the control program overcalculated how much thrust to apply by a factor of 4.45:1, the conversion ratio between newtons and pounds force. Oops!


Sat Apr 03, 2010 10:49 pm
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BC wrote:
- Phobos 2 (1988)
Quote:
The Phobos probes had three identical computers which controlled them. For every operation, the craft would do what at least two of the three computers would tell it to do. Not long into the mission, the first computer failed. As Phobos 2 approached Mars, a second computer began to falter. Three months after arrival, it failed as well. The one remaining computer could not beat the two votes of the failed computers, and thus could not control the spacecraft, which lost contact with Earth on March 27, 1989.

So funky that they gave it that triumvirate control scheme (and there's the notorious Soviet penchant for redundancy again ;)! I'd like to know more about it, because if the computers were identical, you'd think they would have always given the same responses.



Hmmm so after thinking about this a while this is what I think: They were not looking to see if one computers calculations were "correct but different". Im guessing that they were looking for an answer that was bad, or non-exsistant, therefore indicating a complete malfunction of one of the systems.

Whats even more curious is that they wouldnt work out the control scheme that says:
- If 2 of 3 are good - go with the 2, then forever disregard the 3rd's answer.
Then:
- If any 1 is good, go with that. At least this way you continue to have some control.
This assumes that they could logically detect a malfunctioning computer, which would be quite simple I would think.


Sun Apr 04, 2010 7:50 am
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Man I bet if I had a couple clones of myself we could figure this out!


Mon Apr 05, 2010 5:43 pm
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Spirit never did get out of that sand trap, and had to shut down with the onset of the Martian winter and consequent loss of power to its solar panels, which it can't align with the sun, being stuck--and now that it's summer on Mars, it still hasn't woken up, which may mean it's curtains for the rover. More on that and more of Spirit's photos and animations over here.


Tue Mar 29, 2011 10:16 pm
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Posted a bunch of MRO photos of Martian sand dunes over here.


Wed Sep 03, 2014 12:44 am
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