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The Rovers That Just Won't Quit
smooth wombat writes "Like the Energizer bunny, the two martian rovers just won't quit. Spirit, after climbing to the top of Husband Hill during the past year, spent two months examining rocks at the top of the hill and scientists confirmed that those rocks were similar to rocks found along the side of the hill indicating that Husband Hill is probably the result of an impact crater.
It will take about two months for Spirit to make its way down the hill after which the next target will be a feature called Home Plate located about a half mile away.
Opportunity is exploring the northern rim of Erebus Crater, the largest crater between already-explored Endurance Crater and its next destination, Victoria Crater.
The rovers were only supposed to last three months but have been operating for almost two years. NASA has also released a 360 degree panorama of images taken by Spirit as it explored Gustav Crater."
I read Roving Mars a few months ago. It was written by Steven Squyres, the principal investigator for the Mars missions. A very good book with some behind the scenes scoop on the politics and squabbling involved in getting these things build and sent. Highly recommended.
Trolling is a art,
Not to be cruel and kick up their bandwidth, but is a larger version
Well, look at it this way: the rovers were designed with redundancy and robustness so that if things go somewhat wrong they can still provide their target lifespan. A side effect of this is that when things don't go wrong, they exceed their target lifespan.
No kidding!!! What do you say at this point?
It's called Gusev crater.
One of the designers gave a presentation to our conference the day after they landed. It's easy to say they sandbagged their estimate, but they have had a host of challenges such as
So yeah, say they sandbagged it, but in reality, it was entirely possible that they could have worked only for a day (or not at all) and they would have been ostracized for being incompetent when they actually did a fine job. Congratulations to them.
"Who are you?" "No one of consequence." "I must know." "Get used to disappointment."
These babies are solar powered and NASA figured that dust from the atmosphere would render the solar panels useless after two months. The wind kept pushing the dust off the panels so.. there they go again.
believing the big bang requires a certain amount of supernatural faith
They both had a flaw that when their flash memory got too full a buffer overflow in the memory management software would reboot the machine. Spirit had been operating and collecting data first and thus encountered the problem before Opportunity ran into it too. The fix was to disable the flash memory from a safe mode so they could point the high gain antenna and send a fixed software version (once they figured out what was causing the problem). It really was a close call.
There was no landing foam. There were inflated bags that cushioned the impact as the lander bounced. The bags had cords attached to them that were retracted after landing to pull the deflated bags under the lander out of the way. The retraction didn't work 100%, and there was concern that the rover's wheels would get tangled up in the bags or the cords (which turned out not to happen).
The rover actually got stuck on mostly flat terrain. It was crossing some low wind swept dunes which the wheels eventually just dug into (think a car on the beach). By wiggling back and forth they were able to back out, and they added some movement rules for the auto drive that if a lot of slippage occurs the move stops so as not to dig so deep into loose sand.
Coding with assembly is like playing with Legos. Coding an application in assembly is like building a car with Legos.
They aren't over engineered for the environment they were expected to operate in. Our understanding of the martian environment led the engineers to believe that the solar panels would become dirty quickly. I'm sure cleaning systems were considered but a desision was made to have rovers that lasted 3 months without a cleaning machanism. Turns out we didn't understand the martian environment all that well and wind is keeping the panels clean enough to power the rovers. That's just shear luck.
As for the other parts of the rovers out lasting their usefulness - well that just goes to show how good some areas of engineering have become. Yes they could probably have fitted wheel bearings that would seize after 3 months but as they would weigh the same as (or damn near) the ones that have lasted 2 years a desision was made to fit the better bearings. There will always be one weakest component in this case our best guess at what is was was wrong. I'd be interested to know what part eventually fails and kills the rovers. If nothing else this is an interesting experiment into long term rover deployment. I am sure the engineers are getting plenty of interesting telemetry back on what is failing on the rovers.
I used to have a better sig but it broke.
Actually, they are MASSIVE 1 megapixel cameras. The reason I said MASSIVE (in CAPS!) is that the CCD on them is .5 inches square, which is HUGE for a 1 megapixel camera. That means it captures a lot of light and there is very little 'bleed' from one pixel to the next, and it cuts down on the noise in the image. Not only that, each pixel is single color and there are ELEVEN (!!) color filters that can be put in front of the CCD to capture different wavelengths and generate amazing true color images. Their cameras are very very cool.
"False hope is why we'll never run out of natural resources!" - Lewis Black
Very true. The entire MER program was mass-constrained from the get-go. They barely fit on the launch vehicle. At some points during the design cycle the mass margin was negative, and the systems engineers had to hunt around for things to take off. There was no room to spare for over-engineering, because there just wasn't any spare mass for anything other than the bare minimum to achieve the mission. I speak from direct knowledge here, because I sat through the debates about whether or not to have two transponders (final decision: one - the SDST was considered reasonably reliable), and similar debates about the solid-state power amplifiers (the final word I heard was two SSPAs, due to their potential for failure, but that may have changed after I left the program). We used to joke that the only redundant things in the entire systems were the heaters and the SSPAs.