Mars Exploration Rovers Update
26 Oct 2002
(Source: Cornell University)
Week Ending October 26, 2002
Good news: We seem to have solved the "step-and-settle" problem that's been giving us fits for several weeks. The trouble here was that the mirror at the top of our mast didn't seem to be moving quickly enough. Our Mini-TES instrument is supposed to tell the mirror what to do. When Mini-TES is ready for the mirror to move, it sends out a signal that means "okay, I'm done taking data for a little while... go ahead and move the mirror." The mirror has two tenths of a second to get to its new position. Mini-TES then sends out a second, different message that says "okay, you'd better be done moving the mirror, because I'm going to start taking data again." And it starts to collect data, assuming that the mirror has stopped moving.
What we thought was going on was that the mirror was moving too slowly, making the data blurry because it was still moving when Mini-TES started to collect data. But what was really going on was that the mirror was ignoring the first message completely, and starting to move when it got the second message! That'll pretty much guarantee that you're going to get blurry data, no matter how fast you move the mirror.
We were afraid for a little while that this would be a nasty problem to fix, but Jason Gates found a very elegant solution that involved just putting a couple of tiny "haywires" onto one of the rover's electronics boards. We still have a little more testing to do, but it looks like one of our unpleasant problems has now been found and fixed.