Caption: Graphic showing how FUSE would look on-orbit. The telescopes are looking toward the upper right in this picture, and only two of the four telescope doors are visible from this angle. The blue rectangles represent the solar panels, which connect to the spacecraft at the bottom. (Figure courtesy NASA and the FUSE project.)

A revised flight software load to FUSE began on April 16, 2003, as reported in last week's status report. As of this writing, all continues to go extremely well. As of the middle of last week, we already transitioned to a part-time science gathering mode, where testing is done during the day and low-impact science observations are scheduled during the overnight periods. Hence, even as we continue the testing of the new flight software, some science data are being obtained. Continued testing will be on-going for at least the next couple of weeks.

You may recall from previous reports that the project felt the need to protect ourselves from potential future failures of gyros onboard the satellite, which help FUSE maintain stable pointing and move from place to place on the sky. The new flight software is very clever, using whatever gyros are present and operating, but gracefully compensating for any missing gyros. Basically, as gyros fail, we will just keep operating.

To accomplish this feat, we have loaded new flight software to all three computers on board: the Attitude Control system computer in the spacecraft, the Instrument Data System computer in the science instrument, and the Fine Error Sensor (guide camera) processor. This is somewhat akin to performing a "brain transplant" on FUSE while it is in orbit! (I note this is "elective surgery," since we still have operating gyros at this point. But the gyros are a big enough concern that we needed to take this pre-emptive action.)

I will provide another update next week, or as conditions warrant.

Reported by: Bill Blair, Chief of Observatory Operations