ExoMars Options

[Guest_Sunspot_*]

http://news.bbc.co.uk/1/hi/sci/tech/4180840.stm

Europe has fixed on a concept for its next mission to land on the Red Planet.

It aims to send a single robot rover to the Martian surface along with another, stationary, science package.

[djellison]

Of course, with custom realtime OS's - the processing overheads for your average spacecraft are only a fraction of those for the OS's used by those 'mainstream' processors. I've not actually heard of computing performance being a limiting factor for spacecraft - but I may have missed such reports.

Doug

[mcaplinger]

I've not actually heard of computing performance being a limiting factor for spacecraft - but I may have missed such reports.

Generally, Doug is right. There's a lot of semi-informed speculation on this thread, less real info. The RAD750's performance is comparatively poor from two factors: first, the process changes that make its internal registers immune from radiation-induced bit flips slow down the clock speed considerably, but more importantly, external components, also rad-hard, are running more slowly, as are the busses. The RAD750 on MRO doesn't even have an L2 cache and it's using a 33-MHz PCI bus.

If you wanted a non-mission-critical computing resource that didn't have to be totally bulletproof against radiation, there are many options, including commercial processors that happen to be latchup-immune and various gate arrays. For our MSL instruments we are using Xilinx FPGAs; clocked at 40 MHz they are many times faster at doing JPEG compression than code running on a fast desktop system would be.

Rover speed is typically limited more by the capabilities of the drivetrain and the overall power budget. It's not like MER would be going 50 KPH with a faster processor. Despite what AI people will try to tell you, we don't know how to write autonomous nav software regardless of how fast our processors are.

And finally, MIPS (aka "Meaningless Indicator of Processor Speed") is a bad metric for judging computer performance in this or any other problem domain.

[helvick]

Generally, Doug is right. There's a lot of semi-informed speculation on this thread, less real info.
...
And finally, MIPS (aka "Meaningless Indicator of Processor Speed") is a bad metric for judging computer performance in this or any other problem domain.

Thanks for jumping in Mike - you are dead right on both of the above. I used Mips quite arbitrarily and without enough qualification but the intention was to find some metric that emphasized how extremely different the stuff that has to fly is from what we can put in general purpose PC's.

On the issue of rover speed I was trying to show that there are situations where the current rovers' progress is, to some degree, limited by the electrical power that the onboard computing systems consume during the compute intensive semi autonomous driving modes. I agree that any "improvement" in that would not necessarily lead to a faster rover but it would free up some power for other things.