[X] My Assistant

[djellison]

http://www.oobject.com/category/cars-in-space/

I think you know what to do Yeah - the LRV's were cool - but they did the job they were designed to do. MER has done that, and then some.

MERFTW (and Stooke - none of that Lunar nonsense )

Doug

[dvandorn]

I will disagree slightly with Doug here on his elevation of the MERs because they've outperformed their design criteria.

For one thing, the MERs were *not* designed to complete the 90-day primary mission. They were designed to last far longer, per Steve Squyres in his memoirs. According to the best thinking and best knowledge of Martian conditions (based on some hard data from other landers), the MERs were designed to operate until the dust accumulation on the solar panels drove power levels below a sustainable level, and that period of time was reliably determined to be somewhere between 200 and 400 sols. According to everything we knew about Mars, there should have been no way for the MERs to last longer than that -- surviving a Martian winter, for example, was considered an impossible task, preflight.

We found out about cleaning events when the girls were getting into some pretty power-strapped states, though to their credit they had lasted longer at that point than was predicted. The periodic cleaning of the solar panels was an unforeseen boon. The MERs would never have lasted as long as they have had not Mars provided them with an unpredicted gift of cleaning winds.

So, the extreme longevity of the MERs is more due to serendipity than to their admittedly excellent designs.

And, to be fair, because they have lived far longer than their creators ever intended, they're both showing signs of old age. Instead of dying gracefully under predicted dust accumulation conditions, they are developing bum wheels, arthritic joints, blurred vision and low-energy listlessness. They are more like denizens of a senior citizen's home than noble explorers by now... which makes every byte of data we get back from them that much more sweet.

I'm impressed and pleased by how much information our intrepid rovers have amassed. But I don't credit the engineers who built them, or even the rovers themselves, for their great longevity. I view *that* as a series of gifts from the gods.

-the other Doug

[djellison]

The MERs would never have lasted as long as they have had not Mars provided them with an unpredicted gift of cleaning winds.

The wind has made it POSSIBLE for them to live this long. However - that's only an enabling factor. The rovers have still been using that power for barely short of 20x what they were asked to. 20x more wheel revolutions. 20x more camera mast movements. 20x radio transmissions. 20x charge cycles. 20x thermal cycles on all the electronics. 20x more arm movements.

Yeah - they're getting arthritis - but to say it's all down to luck that they're still around is grossly unfair and inaccurate. It's down to damn good engineering and a lot of hard work - designing them, building them, and keeping them alive on Mars.