MER Status Report Week Ending January 25, 2003

Time is getting short, and we’re killing off problems as fast as we
can. We just got another one.

This was a strange one. During a test we did back in December,
something odd happened to our APXS instrument. During a two-hour
test, the instrument somehow got reset — that is, it got turned off
and back on again — seventeen times. That kind of thing isn’t good,
and if it happened on Mars we’d lose data, just like you can lose
data on your computer if it gets turned off before you’ve saved
something. We couldn’t figure out what was wrong, and it looked like
it could be a real problem.

After a lot of sleuthing, the answer became clear. During the same
two hours that we were testing the APXS, the rover engineers were
testing the rover’s power system. That means they were working with
things like the batteries, the electronics that run them, and so
forth. And during that time, what we learned was that they had sent
seventeen different commands to the power system. That was the clue
we needed to solve the mystery.

When we dug in deeply, we discovered
that there is a nasty bug in the rover design: every time somebody
sends a command to the power system, it inadvertently turns the APXS
and the Mössbauer Spectrometer off and back on again! It’s such a
goofy bug we didn’t believe it at first, but that turned out to be
the problem. We’re fixing it with a change to the software, and next
month when we do the same test with APXS on the other rover, we’re
expecting it to behave itself.