Computer swap on Curiosity rover

Mar 01, 2013 by Guy Webster
This artist concept features NASA's Mars Science Laboratory Curiosity rover, a mobile robot for investigating Mars' past or present ability to sustain microbial life. Credit: NASA/JPL-Caltech

(Phys.org) —The ground team for NASA's Mars rover Curiosity has switched the rover to a redundant onboard computer in response to a memory issue on the computer that had been active.

The intentional swap at about 2:30 a.m. PST today (Thursday, Feb. 28) put the rover, as anticipated, into a minimal-activity precautionary status called "safe mode." The team is shifting the rover from to operational status over the next few days and is troubleshooting the condition that affected operations yesterday. The condition is related to a in linked to the other, now-inactive, computer.

"We switched computers to get to a standard state from which to begin restoring routine operations," said Richard Cook of NASA's Jet Propulsion Laboratory, project manager for the Mars Project, which built and operates .

Like many spacecraft, Curiosity carries a pair of redundant main computers in order to have a backup available if one fails. Each of the computers, A-side and B-side, also has other redundant subsystems linked to just that computer. Curiosity is now operating on its B-side, as it did during part of the flight from Earth to Mars. It operated on its A-side from before the August 2012 landing through Wednesday.

"While we are resuming operations on the B-side, we are also working to determine the best way to restore the A-side as a viable backup," said JPL engineer Magdy Bareh, leader of the mission's anomaly resolution team.

The spacecraft remained in communications at all scheduled communication windows on Wednesday, but it did not send recorded data, only current status information. The status information revealed that the computer had not switched to the usual daily "sleep" mode when planned. Diagnostic work in a testing simulation at JPL indicates the situation involved corrupted memory at an A-side memory location used for addressing memory files.

Scientific investigations by the rover were suspended Wednesday and today. Resumption of science investigations is anticipated within several days. This week, laboratory instruments inside the rover have been analyzing portions of the first sample of rock powder ever collected from the interior of a rock on Mars.

NASA's Laboratory Project is using Curiosity to assess whether areas inside Gale Crater ever offered a habitable environment for microbes. JPL, a division of the California Institute of Technology in Pasadena, manages the project for NASA's Science Mission Directorate in Washington.

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antialias_physorg
2.3 / 5 (3) Mar 01, 2013
Diagnostic work in a testing simulation at JPL indicates the situation involved corrupted memory at an A-side memory location used for addressing memory files.

Ouch. Corrupted memory in the FAT is the worst place for a memory error to occur.
Kedas
not rated yet Mar 01, 2013
Does anyone have an idea how long this flash memory was supposed to work MTBF?

Also no info about how much (%) of it can't be used anymore.
antialias_physorg
1 / 5 (1) Mar 01, 2013
Components are usually way overdesigned for the duration of the mission.

The problem is that if they are consigned to have their file allocation table in a certain memory block then the entire memory is now unusable.

(Unless they have a direct connection to the B-side. In which case they could store the FAT there and address the A-side memory with it - which at least would increase available memory. But it would still mean that if the A-side is no longer a back-up in case the B-side fails)
trekgeek1
4.4 / 5 (7) Mar 01, 2013
Diagnostic work in a testing simulation at JPL indicates the situation involved corrupted memory at an A-side memory location used for addressing memory files.

Ouch. Corrupted memory in the FAT is the worst place for a memory error to occur.


Not true, the worst place for a memory error to occur is on Mars. Sorry, I had to do it.
philw1776
5 / 5 (1) Mar 01, 2013
I know SpaceX uses LINUX but don't know what Curiosity uses. I'd be really disappointed if the design required a specific immovable location for the FAT as memory location failures are expected to occur. You'd think that once they're CERTAIN of the problem, they could run a routine in the alternate memory space to restructure the primary.
PPihkala
not rated yet Mar 02, 2013
I think they should (and are?) running flash file systems that allow marking portions of memory as bad, mapping them out of use. And they probably will do such a test and markup on A-side memory, now that they are aware of the problem and are running at B-side.
antialias_physorg
1 / 5 (1) Mar 02, 2013
I'd be really disappointed if the design required a specific immovable location for the FAT as memory location failures are expected to occur.

Some stuff is just hard coded in the BIOS. No matter how modular/flexible your architecture you always have at least one point that is fixed. And it's not uncommon on such low level/high reliability machines that the structure of the FAT and FAT location are one of the hard coded things.

You could always reflash the BIOS - but that is something you only do if there is no other option (because if that fails then your Mars rover is just a hunk of metal sitting there forever.)

philw1776
not rated yet Mar 02, 2013
If memory size is not a real premium as I think it is not with Curiosity, there are redundant architectures that can have a BIOS alternate elsewhere in memory with support silicon. All this is even easier to implement given a separate B side complete computer system. NASA SW types would also likely analyze the internal structure of the memory & chips to ensure that there was not a common failure point linking the back vs primary location. If a telecom startup with a few engineers can do this, then NASA's much larger and smart staff could and should have. On reflection, we really don't know enough about their internal architecture to comment intelligently, but that never has stopped me before.
Jo01
1 / 5 (1) Mar 02, 2013
Diagnostic work in a testing simulation at JPL indicates the situation involved corrupted memory at an A-side memory location used for addressing memory files.

Ouch. Corrupted memory in the FAT is the worst place for a memory error to occur.


I sure hope it isn't FAT.
Radiation hardening (anyone?).

J.

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