NASA rover reboots twice over Easter weekend Options

[Deimos]

NASA rover resurrected twice over Easter weekend

Moderator adding: the JPL press release is here.

[monty python]

One hopes that Spirit isn't seeing some wear and tear from the computer doing very many reboots at the start of its mission. Didn't Spirit just have some computer issues before the latest software upload?

And how does this effect Oppy. Does it stand down to see if a common software bug could effect it?

Brian

[RoverDriver]

One hopes that Spirit isn't seeing some wear and tear from the computer doing very many reboots at the start of its mission. Didn't Spirit just have some computer issues before the latest software upload?

And how does this effect Oppy. Does it stand down to see if a common software bug could effect it?

Brian

I am on vacation this week (Spring Break with my kids in the PNW) so I do not know what's going on on at Gusev. I know Opportunity is driving (forwards!!).

Related to computer booting: I don't think that adds wear and tear. I know of a company that built an empire around computer rebooting.

Paolo

[helvick]

I don't think reboots should affect much but Flash memory does degrade with use. It takes a while but we are running into fairly large data volumes for the lifetime of the rovers. I'm pretty sure that the type of Flash memory used in the MER's is good for around 100k write cycles per cell but five years with a few tens of GB of data throughput in the relatively harsh environment of the Martian surface might be enough to start seeing more frequent transient errors if there was any significant "hotspot" on the Flash drive that was getting a lot more write activity than the average. However I suspect that if this was the root cause Opportunity would be more likely to exhibit the problem as I'm pretty sure she has delivered more data - and given the use of deep sleep mode any wear that was related to the boot process should also hit Opportunity sooner than Spirit since the former has made much more use of that than Spirit IIRC.

Here's hoping it was just some freak occurrence of cosmic ray hits.

[stevesliva]

I don't think reboots should affect much but Flash memory does degrade with use. It takes a while but we are running into fairly large data volumes for the lifetime of the rovers. I'm pretty sure that the type of Flash memory used in the MER's is good for around 100k write cycles per cell but five years with a few tens of GB of data throughput in the relatively harsh environment of the Martian surface might be enough to start seeing more frequent transient errors if there was any significant "hotspot" on the Flash drive that was getting a lot more write activity than the average.

Even if the memory doesn't use the algorithms that balance write cycling (and flash architecture usually needs only balance by sectors or pages or whatever the minimum memory chunk is that can be erased before reprogramming, not by individual bit), it's worth bearing in mind that, like a rover with a 90-day guarantee, each individual flash cell has a 100k (or more) guarantee, but the average flash cell will achieve far more than that. And if there is overhead in the ECC, a single bad bit isn't going to kill the word.

[tanjent]

...it's worth bearing in mind that, like a rover with a 90-day guarantee, each individual flash cell has a 100k (or more) guarantee, but the average flash cell will achieve far more than that. And if there is overhead in the ECC, a single bad bit isn't going to kill the word.

I don't know whether to interpret the 100K cycles "guarantee" as a minimum, mean, median, or even a modal value. But surely the second moment must be important in this sort of problem. If the sigma for expected failure is wide enough around say, 100K, and if a particular programming operation "samples" from say 20KB (WAG) worth of cells, the chance of the program crashing must become significant long before the average cell accumulates 100K read/writes. (I take it ECC refers to some kind of error correction, which probably can catch and correct the early failures if they are rare enough.)