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Mars Rovers Update
BoldAC writes "CNN is reporting that engineers will upload a software hack to decrease the recent power drain plaguing the rover Opportunity. The hack works by reducing the power supply to a poorly functioning switch." p3tersen writes "Opportunity has photographed a blue martian sunset (it's blue because of the optical scattering properties of dust in the martian atmosphere). In other news, the rovers are beginning to experience power supply problems due to the accumulation of dust on their solar panels."
For an easy solution see: helmets of Formula One drivers.
I'm a chainsmokin' alcoholic sociopath, so-ci-o-path
The problem was probably caused by some incompatibility in the Java system
Repeat after me.
There is NO Java on the rovers. Java is used on the ground to process the results.
Idiot. Enough has been posted on this site about where Java is being used.
Doesn't one of their robot arms have a brush device for brushing off rocks?
The ONE robot arm cannot articulate to a position to reach the panels (it is mounted underneath). Also, the brush is made of wire. Not something you would want rubbing against a solar panel.
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I am a programmer. I am paid to produce syntax not grammar. Deal with it.
Um, I seem to recall they knew about dust problems well before they launched. This isn't something that has surprised the engineers. I remember that was the main reason they said they were planning for a 90 day mission, since beyond that point the cells wouldn't charge enough due to the dust.
I've also seen on SpaceFlight Now reports that projections show they will be probably be able to run both rovers well beyond the initially planned 90 days, so they're looking into plans for extended missions now.
However, like others on the thread have wondered, why not devise something to remove the dust? I'm sure there must be a good reason why they didn't do something - I can't imagine the NASA engineers simply didn't think about this.
Don't mod the above off-topic, it's still about space! I submitted this story yesterday and it was rejected :( so here is probably the only place you're going to see it and it's really interesting imho! Cassini is entering the final phase of its 7 year journey to saturn and starting now will be sending back images and other measurements at a "rapid and steady pace". In a few months Cassini will enter orbit around Saturn after performing what should be a spectacular ring plane crossing.
- "Hear that?! The percolations are imminent! Cease your ingress!"
...to have the dust wiped off the rover's solar panels, it has many disadvantages. It has been discussed widely here, even by rocket scientists. In short, it is extremely difficult to come up with a "cost-effective" (from several viewpoints) mechanism. An interesting fact is that the cost of operating the entire mission is around US$ 3m a day, and that must also be considered when determining how long these wonderful bots rover through Mars unveiling its mysteries.
The revolution will not be televised.
How is the motor supposed to pull the correct wire (you wouldn't use thread)? Ten different motors?
A simple set of 10 mechanical gears made of plastic and stacked in a row would do this. The driving gear jumps from first to last as needed. My printer does something similar to this everyday to a precission of 720 dpi so...
What do you do with the tear-off once you pull it?
Cut the wire between the plastic sheet and the gears that rolled the wire. No need to have 10 cutting devices, since only one wire will get rolled at a time.
Don't forget that you have to pack all of this onto the rover and fold up the panels.
Implement one of these in each fixed panel, not in the panels as a whole.
All of this stuff takes up weight and adds complexity
Sending 2 probes to Mars and getting scientific data back is waaaaay more complex than this. And the weight... it adds a little more $$ for fuel, but the result is a _much_ longer lifetime.
this is slightly OT, but "real-time" in engineering circles does not mean "really fast." it means that there is a guaranteed response from the system within an specified actual time frame.
i.e. I need a real-time OS & software stack if my rocket control algorithm needs the data from, say, a serial port altimiter within the next 20 milliseconds or else. if you cant get the data within the specified timeframe then the results are useless. the system will not accept requests that it cannot "guarantee" to fulfil from a system resource standpoint. (you have to watch your multitasking, swapping and other kernel-level tasks to achieve this)
so you could have a 20 mhz "real-time" system, as long as it's response was guaranteed by the OS within parameters for what you are doing (and you would program with those guaranteed response times in mind.) Conversely, a 20 Ghz system may not qualify for real time, if the OS pre-empts your rocket control task and decides to swap for a few milliseconds too long, or context switches to another thread just when you needed to adjust a control surface...
when you hear about people hacking linux for real-time work, they are not making it go faster (though that's always nice), they're making it work predictable.
The updates include improved driving software, something that only evolves after some hands-on time on Mars itself. The patch to strangle the errant heater is pretty drastic - it shuts down some primary circuits including the internal clock, which has the -side- effect of cutting off power to the heater overnight. The rover will wake up the next day only when it starts to get some sunlight on its' solar cells - not by an alarm clock as it does now. The heater will still run once the rover wakes up the next day.
======= ~\_/~\_O Burmese
It's a neat little $10 million 50 kilo unit. The best part is that a software upgrade improved the stability 10x. Hopefully there'll be some pictures soon.
One line blog. I hear that they're called Twitters now.
RTGs are designed to survive rocket explosions, and even re-entry. They're basically armored warm bricks; the plutonium is present in the form of dioxide ceramic.
In 1968, a SNAP 19-B2 RTG landed in the Pacific after its launch vehicle failed to reach orbit and was destroyed. They fished it out and re-used it on a later mission. Apollo 13's lunar module also had an RTG which re-entered and landed, intact, in the Pacific. No nuclear material was released.
The Challenger explosion generated pressures well under 2000 psi. The theoretical worst case for a hydrogen-oxygen explosion is 2075 psi, with a reflected peak pressure of 5300 psi. RTGs are designed and tested at 19,600 psi.
Shuttle explosions won't cause a release of nuclear material from an RTG. They're not only designed for such failures, they've been tested to survive them, both in the lab and in real life failures.
My understanding is that a variety of dust removal techniques were considered. The final decision was that an effective dust removal aparatus could be added, at the cost of any one of the instruments. The scientists decided limited life with more instruments was more useful, and so the dust removal system was left off.
So why nukes for Viking, and none for MER A & B?
1) Viking had money. Sure, NASA was getting into a budget hurt locker by the time the missions made it to Mars in '76, but the money was there when it was needed during the planning and construction. The landers got the kitchen sink, and the biggest Titan II launchers then avaiable to get 'em going. By contrast, the MER team had to make sure their package was not much heavier and absolutely no bigger than Pathfinder. The planetary missions are bastard stepchildren to a NASA which is mandated to keep the Space Shuttle and ISS going on an inadequate budget, even if it all went to the manned space program.
2) Three Mile Island, Chernobyl. Hadn't happened yet, so the no nukes crowd was still the wacko fringe during Viking. Compare to the fuss made over Cassini before launch and while making a gravity-assist Earth flyby. "200,000 deaths!" "Dump it in the Sun!" In general, people have mellowed out a bit, but the PR angle makes a good excuse when one doesn't have the money to gold-plate a mission, anyway.
Luke, help me take this mask off
It's not a case of a few more $$ for fuel. It's a case of being able to launch at all. The rovers BARELY made it under the max launch mass. They were even over the max at some points in the program, and were stripping off mass whereever they could. Besides, in the space business additional mechanisms are frowned upon due to both the difficulty of designing a mechanism to work in the space (or martian) environment, and the inherent decrease in relaibility of the overall system. MER already has far more than mechanisms than is usual for a space mission.
I attended a seminar last week with David Des Marais of NASA Ames reserch center. He noted that, while the panels were covered with dust, the rovers were still maintaining greater than peak power. He specifically stated that the rovers were shunting power because they couldn't store anymore. They suspect that the rovers will far outlive their contracted period.
Sure, try Jupiter, or mabye Uranus. Of course, they aren't nearly as prominent; Saturn's rings are the only ones that can be easily seen by an amateur observer. However, I'd think that any solar system with gas giants has a decent chance of having ringed planets, as it's really just dust and rocks that have fallen into a stable orbit and haven't globbed together into a moon. We couldn't really directly detect ringed planets around other stars from Earth; the distances are just too great. It would be great, though, to send some sort of interstellar probe to a distant solar system and have our heirs recieve images of a Saturn-like ringed planet.
That's it. I'm no longer part of Team Sanity.
So I just happened to be lucky enough to get front row seats (I work as a sysadmin in the physics department here) to a talk by one of the people on the JPL team that works on the lander, and he mentioned this earlier. It's a bit more than a little hack to the software because it involves changing out the operating system and turning the rover completely off during the night to avoid power drain. What the fellow talking about it mentioned was that there is the possibility that the rover wont actually turn back on after the update, leaving a $400 million piece of junk on the surface of mars.
The reason for the update is needed because there is a heater on the rover that defrosts the probe that allows them to take samples from the rocks and such--which wont turn off anymore. This might not be a problem except that it puts an excess power strain on the rover, meaning that its useful life is greatly diminished. So essentially this hack means turning everything off at night because they can't switch off just the heater.