To: sot_shift Subject: B3 shift report Date: Sun, 25 Jul 1999 22:41:26 -0400 From: Ed Kellogg -------------------------- July 25 11:49 am - 11:49 pm SOT Lead EMK FP Sci MJ Spac/Aspect TA FOT/Sci liason - HRC GKA,KD ACIS YB There were few events on this shift: ACIS temkperature monitor, and IPS burn #2. 206:22:57 GMT another look at ACIS focal plane gives -118.9C, just under three hours from perigee. 207:02:01 IPS burn #2 went very smoothly. This one lasted 11 minutes, at apogee. The new perigee is predicted to be 3448 km. Apogee is still 72070 km.(see IPS burn #2 worksheet 02:36 We reviewed Replan package B3, which has new DSN view periods, moves HRC door opening earlier, includes early activation of fidlights and ACA, repeat of HRC-S pulse inject, move of ACIS partial bakeout time, and some format 2 data around perigee #3 to investigate thermal behavior of ACIS more. ACIS focal plane temperature ---------------------------- More plots made by Tom (flt note 71) tell us that after perigee, the ACIS warm radiator, cold radiator, and camera body all cool down together until the body hits -62C. At that time the detector assembly heater current comes on, and the temperatures of all three stabilize until Chandra approaches the next perigee. Then the heater goes off and all three rise. This is suggestive that the radiators are being temperature controlled by the detector assembly heater. If so, the cold radiator may not be able to get down to a low enough temperature to permit the focal plane to reach -120 C. Perhaps this is why the FP is reaching only -118.9 C. We plan to gather more data using format 2 near the next perigee, #3, to see if we can track the focal plane temperature along with the tlm points discussed above. Bart is working this issue. EPHIN rates are higher than predicts, not surprising in the current orbit, at lower altitudes than the final orbit. Replanning is under way. The big issue is when to open the ACIS door. A meeting is being planned, with Garmire, Mayer, Theiss, Schwartz and others. Tradeoff is between keeping the time after launch to 11 days vs. waiting until after the last IPS burn, a bit longer. Tony Lavoie is involved.