Subject: B6 shift report Date: Wed, 28 Jul 1999 20:58:00 -0400 From: Tom Aldcroft Shift B6. Start at 209:13:20 GMT = 0920 am 28 July 99 End 9:20pm 28 July 99 SOT Lead TLA Spac/Aspect MF FOT/Sci liason MJ HRC JG,EJ ACIS YB Events: ** Day 209 - OBC telemetry grid for radiation was uploaded and correct performance verified 14:00 - 22:00 - Earth scan 10, completed normally ~16:00 - Some excitement from the ACA. Around this time we noticed that 3 of 4 fid lights had been dropped, the monitor windows were showing negative count rates, and the remaining fid light was sitting on a background of 2800 counts per second. Two slots which had been tracking a fid were now idle, while another was now indicating a "Lost image" status. The cause turned out to be stray light from the sun-shade door, which became very strong when we maneuvered for the Earth scan. This is a known feature of the sun-shade door, and is not expected to be an issue once it is opened. A flight note with full details will be issued. ** Day 210 00:35 - ACIS dark current readouts started 20:00 - Focus flexures on -z side of s/c is hot with the sun at 45 pitch,This due to sunlight entering the SIM/OBA closeout. This temperature is beyond setpoints, beyond hot-case about 13 degrees warmer, and would produce a gross alignment shift. TRW thermal is considering changing setpoints from +10 C to 24 C to give good alignment. This is new, and we have never driven them that high before. Thermal wants to spend many hours, along with tests at different attitudes. An action plan for this is being developed by a mini-tiger team.