[X] My Assistant

[maycm]

From the following "Space" article LINK

Spirit’s solar arrays currently produce about 650 watt hours while Opportunity’s generate up to 700 watt hours, Laubach said. A minimum of 300 watt hours is required for Spirit to function, though Opportunity can operate on slightly less, she added.

What is the reason for the lower power requirements of Oppy?

I thought the two rovers were identical.

[Guest_PhilCo126_*]

Are all the drive motors on the wheels in operation?
( Spirit had a problem with a right front wheel drive motor ... )

[Marcel]

Are all the drive motors on the wheels in operation?
( Spirit had a problem with a right front wheel drive motor ... )

Yes they are. Spirit indeed HAD a problem with its right front wheel, drawing more current due to increased friction, which disappeared after the new driving strategy (driving forward and backwards alternately) was introduced. The wheel problem was probably caused by the way the lubrication was distributed due to turning in the same direction all the time. Now it's fine.

[ljk4-1]

TWIN MARS ROVERS STILL EXPLORING AFTER TWO YEARS
------------------------------------------------

With a longevity unthinkable even to the humans that built them, NASA's
remarkable Mars rovers remain hard at work after two years on the Red
Planet's surface. Both motorized robots are still going strong in their
continued scientific pursuits.

http://spaceflightnow.com/news/n0601/24marsrovers/

[sattrackpro]

TWIN MARS ROVERS STILL EXPLORING AFTER TWO YEARS

Thanks for the pointers to the articles !!

There is an interesting dichotomy emerging - highlighted by the differences between the first paragraphs of the articles from Cornell and Spaceflight Now.

“The Mars rovers Spirit and Opportunity have nearly tripled their expected lifetime on the Red Planet.” – Cornell Daily Sun

“Spirit and Opportunity reached the Red Planet on January 3 and 24, 2004, beginning planned 90-day missions...” – Spaceflight Now

We’ve been told that the life expectancy of the rovers was 90 days (that is all they were guaranteed for.)

Remember when Spirit got to 180 days it was said the mission had ‘doubled the expected life.’ *) hence, you would think that if they lasted 270 days, they would have ‘tripled’ their ‘expected lifetime’ – and that today we would be hearing that Spirit has been going over eight times it’s expected lifetime.

But, now we learn from Squires that, "All the components in the rover were designed to last the equivalent of 270 sols before we launched and we've now been on Mars more than 700 sols."

I’m beginning to wonder if NASA/Squires/et al, are now beginning to worry that they may be accused of initially misleading the world as to expectations, i.e., it is less extraordinary that missions last only three times the expected than it is that they would surpass the expected by a great deal more than eight times!

It's a funding thing, you know...

* Two links that speak of doubling at 180+ days...
NASA says 'doubled its primary mission.' - see caption under photo 'Mars Rover A Big Hit'
Discover.com says 'doubled its expected lifetime'

(I hope fortune remains with these missions, and we see survival well into the future !!)

[mcaplinger]

But, now we learn from Squires that, "All the components in the rover were designed to last the equivalent of 270 sols before we launched and we've now been on Mars more than 700 sols."

It's standard JPL practice to design and test things for 3x the expected mission life. So they planned for a 90-day mission but had test data that said they could last for 270 days if conditions were as expected.