Spirit is coming to the end of it's 90 Sol primary mission and Opportunity is not far behind. The bloke in the press conference with Bethany Ehlmann said that both Rovers were showing no signs of wear and tear and that all the drop off in performance was due to environmental factors such as dust, availabilty of sunlight, temperature etc. They're talking about a 90 sol trip by Spirit to Columbia hills, doubling the 90 sol design life, and I assume they're also going to want to have a look around when they get there. So, when will the missions end? Will they keep going until the rovers simply wont work any more? Or will there be a cut off point based on time and money to run the mission from Earth?

Also, what do you think will 'kill' the rovers? Mechancal failure or environmental factors? Which will stop first?

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Opportunity will not be "taxed" as to its abilities in the coming weeks (less power draws, more idle time [for what idle time it does have]), because of its flat, rockless location. Opp. will make it to the larger crater in record time.

Spirit must use more of its capabilities in navigation and locomotion which means more "wear and tear" on its drive-train, because it is surrounded by obstacles. I hope Spirit makes it to the top of the Columbia Hills, but I won't "hold my breath". It would be cool to see the panorama from up on top, though.

I thought these rovers were solar powered with rechargeable batteries? Or will those batteries loose charges over time until they're useless?
Anyway, I say Oppurtunity since it hasn't had a computer problem. Yet. But also, its in what appears to be a smoother terrian. Less obstructions and damaging rocks. So far.

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Remember, Opportunity has had that power drain from the malfunctioning heater element that is sure to take its toll on the longevity of the rover.

"I thought these rovers were solar powered with rechargeable batteries"

True, but there are two factors to bear in mind:

1) Increasing build-up of dust on the solar panels will progressively and eventually degrade the recharging process.

2) Both Rovers are in the southern hemisphere which is entering winter which means shorter days with decreased amounts of available sunlight as well as progressively colder temperatures which will begin to effect the overall performance of such things as the mechanical arms.

I saw one estimate about a month ago that both Rovers should begin to show serious degradation by Sol 200 for each.

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My impression was that both rovers are fairly near the equator of Mars, so therefore the day length shouldn't alter that much. In the tropics here on Earth, day length doesn't alter very much and neither does the temperature. I suppose Mars is moving further from the sun, but just how excentric is it's orbit?

Also, the atmosphere is becoming clearer of dust as witnessed by the distant views of Gusev's rim not seen earlier. That may lead to warmer days, but may also mean colder nights.

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They should navigate them toward each other and then have them fight. Advertisers would pay big money to advertise on that TV special. Probably enough for another mission. Of course, it would probably take awhile since they weren't built for speed.

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I never heard about that one.
Perhaps a future rover can be equipped with a brush to dust off its own solar panals to prevent degridation. Just a thought! :wink:

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I calculated the odds of this succeeding versus the odds I was doing something incredibly stupid...and I went ahead anyway. - Crow T. Robot

Godspeed, John Glenn. - Scott Carpenter

And these atomic bombs that science burst upon the world that night were strange even to the men that used them.
- H.G Wells, The World Set Free

To the conspiracy crowd, radiation is a big Boogey Man that inspires terror and death in all who encounter it. - JayUtah

The 2009 NASA Rover will be nuclear-powered and won't need solar panels.

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Ya would think with all this technology floating around, someone would have put a solar panel wiper on there... sheesh!

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It's a question of space, weight, and power; the Rovers have limited amounts of all those available. Including wipers would have meant leaving out at least one scientific-data-gathering instrument, perhaps more.

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True but for want of a couple of 98¢ brushes (and the million dollar gear to make them work) the whole rover was lost. One less instrument could mean the rest could be run much longer. In theory anyway.

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Solar cells also degrade after each charge. They have a very limited life; even with very expensive solar cells. They don't last forever.

I wouldn't even consider dust a problem compared to the short life of solar cells.

Solar cells also degrade after each charge. They have a very limited life; even with very expensive solar cells. They don't last forever.

I wouldn't even consider dust a problem compared to the short life of solar cells.

Since I am the eternal optimist, I am not voting. Think of how far bast its main mission Gallileo made it. Lets keep the faith that they wil surpass expectations.

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A couple of points:

It's generally thought that the dust is very fine - micron size - and sticks to the solar cells electrostatically and couldn't be effectively removed by brushing. But there was suppose to be a series of dust removal experiments on the lander that was cancelled in the wake of the Climate Orbiter failure.

As far as lifetime of the rovers, Steve Squyres said a couple of weeks ago that the projections of rover health out to 240 Sols show them "still going strong" (assuming no mechanical/electrical failures). The atmosphere has cleared significantly in the last 2 months which means more sunlight reaching the solar cells and less dust settling on them. Sol 240 would put them into September, which is near the start of solar conjunction where communications may be disrupted for about two (?) weeks. It's also about the start (note: edited from "end" in original post) of northern summer, so the sun will be as low in the sky as it will get. So if they survive through conjunction, the energy situation will get better as the sun starts heading south (of course, a counter trend is that solar insolation is decreasing as Mars moves towards aphelion). I don't know when they start running into battery recharge cycle limitations. Or maybe the cold will also help zap them by then. But, who knows, if these rovers are as robust as they seem to be, wouldn't it be a hoot to see them roll into 2005?

constible, I don't think the solar cells themselves will degrade with use, but the batteries certainly will. Dust accumulation is the big threat to the solar cells. Batteries are succeptible to charge cycle burn in, thermal variations, less charging time per sol and less solar energy to charge per sol because of the lower sun angle.

Maybe this is a naive question, but why didn't they put wipers on the solar panels? :P

Gee, I thought that I mentioned that above. :-?

There is no evidence that brushing would work sufficiently in the first place and there was no way to justify the expense and effort of designing and installing such a system. It was all they could do build and launch both rovers as is in 3 1/2 years.

The Spirit rover got an extension! How is its condition?
Think a RTG powered rover will someday visit Mars? Then such a probe could last for years! Of course, such a thing would have to be justified.

__________________
I calculated the odds of this succeeding versus the odds I was doing something incredibly stupid...and I went ahead anyway. - Crow T. Robot

Godspeed, John Glenn. - Scott Carpenter

And these atomic bombs that science burst upon the world that night were strange even to the men that used them.
- H.G Wells, The World Set Free

To the conspiracy crowd, radiation is a big Boogey Man that inspires terror and death in all who encounter it. - JayUtah

Spirit is doing well. It is currently in a four-sol stand-down while new flight software is uploaded to it. See here for status.

The planned Mars Science Laboratory (MSL) will be RTG powered. See here for details.

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