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."

Re:Solar problems

[r00zky]

For an easy solution see: helmets of Formula One drivers.

Re:Java problems?

[Anonymous Coward]

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.

Re:Fan

[RetroGeek]

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.

We can put 2 rovers on Mars...

[Anonymous Coward]

...and fix software problems they're having from a control room on Earth, but we can't figure out how to build the equivalent of a windshield wiper to gently clean the dust off the solar panels?

Re:Difficulties in planning space missions

[Gossy]

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.

Re:This just in from Saturn

[deglr6328]

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 [arizona.edu]". In a few months Cassini will enter orbit around Saturn after performing what should be a spectacular ring plane crossing [nasa.gov].

As nice as it would be...

[r.jimenezz]

...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.

Re:Java problems?

[mrtom852]

Some important (I presume) Sun person made the Java on Mars claim at a recent Sun Tech Day. She was quickly corrected by another (more important) Sun guy but it's easy to see how people are getting confused if some Sun sales people are spreading this rubbish.

Re:Solar problems

[Anonymous Coward]

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.

Re:Java problems?

[nehril]

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.

Re:Fan

[DynaSoar]

RetroGeek (206522) sez: "Is there some reason why these rovers do not have a fan to blow away the accumutating dust on the solar panels?"

Lack of air mass. A fan on Mars would be only 1% the efficiency of the same fan on Earth, because there's that much less air. Plus then you're using more power and using up the batteries, to not much effect.

I would have suggested an electrostatic charger, like the old Diskwasher Zerostat, for removing the charge from vinyl LPs, making them easier to clean.

Re:Planning Ahead

[Tablizer]

Maybe it would be better if we tested the software more on earth and had all the bugs worked out before we sent it up.

They had a small time-window to get a lot of stuff ready. Because of the politics of funding, often they only have about a 4-year lead to put it all together. Plus, Mars is only in the right position about once every 2 years.

Re:Planning Ahead

[dellis78741]

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.

Also from space: "Humble" telescope

[AndroidCat]

Might as well toss some more space news in. No pictures yet alas. Tiny telescope exceeds high hopes [thestar.com] May detect clouds on distant worlds.

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.

Astronomy Picture of the Day

[rodney dill]

The APOD [nasa.gov] site had this picture of a "named" rock a couple of days ago.

Re:This just in from Saturn

[Anonymous Coward]

Most of the gas giants in our solar system have some form of ring system, but none of them are remotely on the scale of Saturn.

Re:mainly because people are ignorant

[Anonymous Coward]

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.

Re:Concerning charged particles...

[IgnoramusMaximus]

but this reduces transparency quite a bit,

I am not sure you realize that all of the LCD displays feature transparent conductive surfaces for the electrodes. Hell, most of them have entire circuits that are transparent (TFT = Thin Film Transistor). There are chemicals that are for all practical purposes transparent and are conductive.

The RAT is not exactly a brush..

[SuperKendall]

RAT is short for "Rock Abrasion Tool", meant to remove the upper layer of a very hard rock.

In the same way you'd not be keen to use a RAT to brush your teeth, you probably would not wish to use the RAT to clean a transparent surface of a solar panel. In fact I think you may have just given some poor engineer at NASA a heart attack just by suggesting the RAT come near the solar panels!

That's why OUR sky is blue, silly!

[csoto]

Sunlight = full spectrum. The sky really isn't blue...

Re:Clean Solar cells, Do what porn stars do!

[jaxdahl]

The problem with that is that the dust on Mars is electrostatically charged -- ever open a box with cling wrap and have it stick to your hand? Tried shaking your hand to get it off? Didn't work? That's the problem. The dust won't simply come off if you vibrate the panels.

Re:Solar problems

[Anonymous Coward]

Not exactly. The batteries will fail once the rover cannot put out enough power to keep the warm electronics box that they are in warm. At some point the power put out by the solar panels will not put out enough power to charge the batteries so that they can keep a constant temperature in the WEB. Once that happens, it will cool down so that each successive day the WEB will get colder. This also means that the batteries will have a lower and lower capacity each day (temperature related). This amplifying effect will cause the rapid failure of the batteries a couple of days after the initial loss of temperature control degradation, which will kill the rover once the WEB cools down to normal Mars temperatures.

Re:mainly because people are ignorant

[imsabbel]

Plutonium ISNT the most toxic substance on earth. Its the most toxic base element, but e.g. butolinotoxin has more than 50000times stronger toxic effect.
In fact, the TD50 of Pu236 is compareable to nicotin.

Its not healthy, yes, but it isnt that bad.

Re:Compressed Gas to blow the dust off?

[evanbd]

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.

No_Nukes = Cost * PR^^2

[cmholm]

Some of you may recall that the Viking landers used radioisotope thermoelectric generators (RTG's), the "warm brick" another poster referred to. The landers remained active for up to six years, Viking 1 having been disabled by a boo-boo from mission control. They didn't have to worry much about dust accumulation, and Viking 2 landed at 48deg North, 'way north of the tropical band the MER planners were limited to by solar panels.

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.

Re:mainly because people are ignorant

[Anonymous Coward]

"butolinotoxin has more than 50000times stronger toxic effect [than Pu]."

You mean lethal at 1/50th of a nanogram? Meaning that one gram can kill 50 billion people? You got some proof handy? This I've got to see.

Re:Solar problems

[GileadGreene]

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.

What?

[Anonymous Coward]

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.

Re:Java problems?

[nehril]

There are many aspects of Java that mean you can't guarantee a response within a certain timeframe. Garbage collection, for example ... there isn't necessarily a 1:1 instruction translation of the JVM's bytecode, and therefor you can't know beyond a shadow of a doubt that a certain operation will get done in a certain amount of time.

you can get real-time behavior out of an interpreted system, if both the interpreter and underlying operating system are designed for it. For Java, GC and instruction translation just have to have that as a design goal. As a matter of fact: here's some information on real time Java [sun.com]:

"With the recently released Real-Time Specification for Java (RTSJ), developed through the Java Community Process by the Real-Time Expert Group, the real-time embedded software developer will be able to use the Java programming language in applications where predictable/hard real-time behavior is a must."

that being said, java probably would run too slowly for most applications on a 20 mhz cpu. But being interpreted or having GC are orthogonal issues to real-timeness.

Re:mainly because people are ignorant

[Anonymous Coward]

"Radioactivity and Health-A History" by J Newell Stannard, U.S. Department of Energy, Pacific Northwest Laboratories, Battelle Memorial Institute, 1988, pg 368.

Acute Toxicity of Plutonium Compared to Supertoxics (LD50)

Botulinus Toxin A 5X10E-6 ug/kg
Crystalline Botulinus 7X10E-9 ug/kg
Diptheria Toxin...... 1X10E-4 ug/kg
Bufotoxin............ 390 ug/kg
Curare............... 500 ug/kg
Strychnine........... 500 ug/kg
Potassium Cyanide.. 300 ug/l
Hydrogen Cyanide... 1000 ug/kg
Methyl Mercury..... 7000 ug/kg
Arsenic Trioxide..1000000 ug/kg

Plutonium....... 300-1400 ug/kg

And, just for the heck of it:
Nicotine........ 810 ug/kg

Re:mainly because people are ignorant

[Anonymous Coward]

Hey I can do a web search too. I can even provide attribution:

http://www.vanderbilt.edu/radsafe/9406/msg00038. ht ml

regarding Don Jordan's posting:

That LD-50 for botulinus toxin is wrong. It's usually considered to be
around 0.00001 mg/kg in rodents, i.e., 0.01 ug/kg , not e-9 ug/kg. That's
still super-toxic. By comparison, the LD-50 for dioxin, often called the
"most toxic small molecule," is 100-fold greater at around 0.001 mg/kg in
rodents. But as pointed out, we're comparing apples and oranges since acute
lethality isn't really the issue with plutonium (or dioxin).

Joshua Hamilton Ph.D.
Dept. Pharmacology & Toxicology
Dartmouth Medical School

Re:This just in from Saturn

[PurpleFloyd]

Any other planet with rings?

Sure, try Jupiter [nasa.gov], or mabye Uranus [nasa.gov]. 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.

I attended a talk on this today at Texas A&M

[billatq]

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.