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posted by janrinok on Tuesday June 12, @10:42PM   Printer-friendly
from the we're-rootin'-for-you dept.

The Mars Opportunity rover is caught in a dust storm, and the craft is hunkered down doing its best to survive the intensifying weather. The storm was first detected on Friday June 1st by the Mars Reconnaissance Orbiter, at which point the rover's team was notified because of the weather event's proximity to Opportunity. The rover uses solar panels, so a dust storm could have an extremely negative impact on Opportunity's power levels and its batteries.

By Wednesday June 6th, Opportunity was in minimal operations mode because of sharply decreasing power levels. The brave little rover is continuing to weather the storm; it sent a transmission back to Earth Sunday morning, which is a good sign. It means there's still enough charge left in the batteries to communicate with home, despite the fact that the storm is continuing to worsen.

[...] The main concern here isn't the dust storm itself. It's the need to keep the rover's heaters operational while maintaining a minimal power level in the batteries. This isn't the first storm that Opportunity has weathered, but it is the worst. According to NASA, the weather event the rover faced in 2007 had an opacity level around 5.5. The estimate for this current storm is somewhere around 10.8.

Opportunity is a hardy little rover, though, and it has continually defied our expectations over the last 15 years. The rover was only designed to last for a 90-day mission, and yet it's still going. Here's hoping that Oppy will continue its trek across the Martian surface for many, many days to come.

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  • (Score: 2) by bob_super on Wednesday June 13, @04:37PM (3 children)

    by bob_super (1357) on Wednesday June 13, @04:37PM (#692394)

    > Time on the ground trumps wads of money spent on untested (and thus, unreliable) reliability testing.
    > Let us note in the example above, that you could chain roughly 400 such parts, every one of them a single point of failure,
    > to yield the desired failure rate. I don't think you need that many components on a Mars rover,
    > much less have them to that reliability and redundancy.

    You're somewhere between Dunning-Kruger and amazingly wrong.
    "Time on the ground" is a nine-figures line item, so you build lots of redundancies, and do a lot of testing under all possible conditions, during the ten years it takes to build the rover. Reliability testing is pretty good these days, with is how a rover can last 15 years on Mars, or a few years going through Jupiter's and Saturn's radiation belts.

    With lowering launch costs, sending a bunch of microsats could start to make sense, but landing on Mars, and roaming around sandy terrain while sending data all the way back to Earth, is putting a minimum size requirement (even when the experiments don't), which drives the 9-figures trip, which drives the "make it last" redundancies and testing.

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  • (Score: 1) by khallow on Thursday June 14, @03:34AM (2 children)

    by khallow (3766) Subscriber Badge on Thursday June 14, @03:34AM (#692678) Journal

    "Time on the ground" is a nine-figures line item

    Getting NASA out drops it to an eight-figures. SpaceX and more mass available for a mission (which greatly reduces the need for extreme, and extremely costly, mass optimization) would drop it to seven. Mass production combined with ISRU probably could then drive it down to five-figures though it's a lot of overhead, if you're not settling the planet. Overpriced reliability testing to ridiculous degrees would be one of the early on casualties.

    You're somewhere between Dunning-Kruger and amazingly wrong.

    Do the math yourself. (0.9999^100) ~ 0.99, meaning that 100 such parts each with its own 0.9999 chance of stopping the mission could be introduced and still have a 99% chance of success over a year's time. Reducing that to 90 days means you can quadruple the number of parts and still maintain the 99% chance of success over the shorter period of time.

    What's really futile about this degree of reliability testing is that you aren't doing it often enough to know whether it works or not. Doing it successfully for twenty projects means that you don't know whether it's successful 99% of the time or 95% of the time (a big difference!).

    • (Score: 2) by bob_super on Thursday June 14, @05:20AM (1 child)

      by bob_super (1357) on Thursday June 14, @05:20AM (#692718)

      That's what Beam Time is for.
      You don't just build one each time. You build a bunch (because the cost is in the design much more than the BOM), and test the heck out of a big sample, before picking one.
      Don't underestimate failure analysis and fault tolerance designs. Some of this stuff is really amazing.

      • (Score: 1) by khallow on Friday June 15, @03:52AM

        by khallow (3766) Subscriber Badge on Friday June 15, @03:52AM (#693322) Journal

        You don't just build one each time. You build a bunch (because the cost is in the design much more than the BOM), and test the heck out of a big sample, before picking one.

        Actually, most of the time they do build just one. The MERs were a little exceptional in that they built two.