Aug_14_1999_L23.txt Shift L23 Start at 1999:226:10:00 GMT = 1999 Aug 14 6:00am EDT End 1999 Aug 14 2:00pm EDT See http://asc.harvard.edu/acis/SOT_reports/sot-shift.html, or /proj/ascwww/AXAF/extra/science/htdocs/acis/SOT_reports/Aug_14_1999_L23.txt. SOT Lead Ed Kellogg SOT SC/ACA Tom Aldcroft FOT-SI HRC-SI James Reeves ACIS-SI (Times will be given in GMT on day 2265. not precise.) EVENTS PLAN DONE OBSID -------------- ---- ---- ----- Start shift (06am EDT 14 Aug 1999) 1000 1000 62738 Start operating from DOT 1030 OBSID to 01051 nominal 1047 1050 01051 ACA ACQ got 5 stars, only 1 of 3 fidlites 1047 1050 Maneuver, null move, nominal 1047 1050 ACIS run start, nominal 1051 1051 ACIS stop science 1133 1133 OBSID change 1133 1133 01052 Maneuver ends, only one fidlite again 1138 ACIS start science 1138 1138 ACIS stop science 1219 1219 OBSID change 1220 1224 01264 Maneuver, ACA failed to get guide, went to brt hold 1220 1224 ACIS reports image on S2 chip as planned New OBSID 1249 01265 Maneuver, ACA got acq star, not guide 1304 Decide to stop DOT/SCS after next maneuver 1318 Slewing 1320 New OBSID 1323 01263 Maneuver end 1324 Stop SCS's 128,129,130 - 1325 New OBSID 1350 1347 62558 ACIS enable & activate SCS 190, ACIS acq 0637-752 1350 1350 Canberra LOS 1420 Madrid AOS 1640 End shift (2pm EDT 12 Aug) day 226 1800 NOTES/ISSUES/PROBLEMS --------------------- At H-to-L shift change, 226:1000, Chandra 18 hrs before apogee ACA tracking HRC on, low voltage power only EPHIN nominal ACIS acquiring data Vacuum 4.5e-6 torr COM Goldstone We started the DOT operation on time, but the printed version, md226:0601_a.dot, did not show the update made yesterday to delay some events by 3 minutes. It appears that just the OBSID changes were delayed. At 1325 we stopped the observing program. The ACA was not behaving as desired. One problem is that in a small maneuver, some of the stars being tracked stay in their slots. Then, if they are guide stars for the next target, the system tells ACA to look for them in some other boxes, and it won't search for the same star in another box. This causes a failure of acquisition and we go into bright star mode, which is supposed to activate SCS 28 1650 vac monitor 4.6e-6 torr. As a result of this morning's events, we also decided that we will make the fidlite search box larger. We will also rebuild SCS 28, which is supposed to put us in normal maneuver mode when the ACA doesn't track properly. This morning, SCS 28 was activated and it did other than intended. The rebuild will be tested at TRW on the ASVT and delivered in some hours.