MER 2003/Athena Update Week Ending February 8, 2003

We passed another big milestone this week — our very last vibe
tests. Vibration tests are some of the scariest things you do to
space flight hardware. It’s a torture test: You bolt your instrument
to a machine that shakes it as hard as the rocket will shake it when
you launch it, or even harder. Sometimes the instrument survives the
test, and sometimes it doesn’t.

These were the final vibe tests for our flight APXS instruments. We
should have done these tests many months ago, of course, but
sometimes things don’t work out the way you’d like them to. Several
months ago we discovered a very bad mistake that we had made in part
of the APXS that detects alpha particles. This “alpha mode”, as we
call it, is essential for detecting important elements like carbon,
and it simply wouldn’t have worked on Mars the way we originally
built it. At least we found the problem in time! But it meant that we
had to go out and get new and improved alpha detectors, put them in
the instrument, and then do all the testing months later than we
originally wanted to.

If we hadn’t passed the tests this week, we would have been stuck
flying our spare APXS instruments. The spares are okay in most
respects, but their alpha detectors won’t work right because of the
design mistake we made. So it was with enormous apprehension that we
shipped the APXS flight instruments, with the fixed alpha mode
included, to Berlin for their final vibe tests. They both passed
beautifully, and soon they’ll be ready to go on the rovers. It’s an
enormous relief.

MER 2003/Athena Update Week Ending February 8, 2003