[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'm not trying to belabor a point, here, but it's the "20x" statement that's specious. The MERs have *NOT* performed 20x longer than they were designed to perform. They have performed 20X longer than the primary mission, but they were designed to perform for far longer than their primary mission. Again according to Steve Squyres, when his team figured out how to get the extra solar cell strings onto the rovers, he knew he had a pair of vehicles designed to last not just for 90 sols, but until dust accumulation killed them -- which they thought would be at least 200 sols, and with some luck perhaps as much as 400 sols.

They were *designed* to last far longer than 90 sols. To say that they have outperformed their design lifetimes is valid -- to say that they have outperformed their design lifetimes by a factor of 20 is specious. The factor that they have outperformed the lifetimes *actually* envisioned by their creators is more like 4x to 8x. Still impressive -- but not 20x.

That's all I'm saying...

-the other Doug

EDIT: It also just occurred to me that you also have to ask at what point does reduced functionality cause you to say that a vehicle has stopped performing, at least in a given area? Neither MER is currently operating up to spec -- Spirit is so power-starved she's a barely-active rover, and has had no RATting capability for quite some time now. Neither mini-TES is working at the moment, though my understanding is that Oppy's may be revived at some point. The radioactive sources for the APXS and Mossbauer have faded so far back that integrations that used to take a few hours would now take many, many sols, and the quality of the results goes downhill as time goes on. Has a MER that is at, say, 50% of its design operational capability actually still outperforming its design lifetime? How about 20% Or less? Do we consider a MER that can take a single image a month and can no longer move a still-operational MER? Just wondering... dvd

[djellison]

The radioactive sources for the APXS and Mossbauer have faded so far

Mossbauer, yes. APXS, no. MUCH longer half life for its two sources - 18 years for one source, 6500 for the other.

Stating the APXS is faded significantly is entirely untrue - so I thought it worth correcting.