To: sot_shift Subject: B2 shift report Mime-Version: 1.0 Date: Sat, 24 Jul 1999 23:12:49 -0400 From: Ed Kellogg Content-Type: text/plain; charset=us-ascii X-UIDL: 5284cdc68bfa5831e10dea2abc5b8e5e --------------------- Shift B-2. 205:15:48 to 206:03:48 GMT 11:48 am to 11:48 pm July 24 SOT Lead EMK FP Sci MJ Spac/Aspect TA FOT/Sci liason - HRC GKA,KD ACIS YB (Times will be given in GMT) 205:17 - flt note 046, ACIS FP temperature. We haven't still reached -120C. Cold radiator gets quite warm as we pass near the earth, and FP goes above its lowest recorded point of -118.9C. ACIS focal plane temperature is varying, increasing at perigee and dropping away from perigee. The thermal people, Lee Harper and Ellen Sen, presently feel this is normal, and should be watched as we raise the perigee with IPS burns. Ellen thinks we could consider dropping the FP setpoint at ~ IPS3. This might not be necessary if things cool off with the higher perigee. Earth scan: ------------------- We compare the position of the earth as observed with the Earth Sensor Assembly (ESA) to that predicted. On earth scan #1, we are comparing with the prediction from the known orientation of IUS at launch in the tower, updated with the IUS gyros. The IUS solution is said by IUS team to be good to 0.25 degree 3 sigma. This attitude is propagated and updated after separation using the Chandra sun sensor and gyros, including an update to the Chandra gyro biases from the sun sensor data. We then compare that prediction for the angle of the earth with the observation by the ESA. 205:18:15 - Preliminary results from Earth Scan #1 On the descending leg, the only good ESA data were at low altitude, where accuracy is known to be lower, the difference between predicted and observed was 0.8 to 1 degrees. On the ascending leg, where we were at higher altitude and got more accurate data, the difference calculated is ~0.1 degrees for ESA2 and ~1 degree for ESA1. The ascending leg result for ESA1 is comparable to the expected overall error of ~0.5 degree. The result for ESA2 is much smaller, but the average of the two is just about equal to the overall expected error. This expected error is based on sensor noise, alignment, and ground calibration of the ESA sensors. These results indicate that the attitude is known well enough for IPS burn #1. This will be re-evaluated in Earth Scan #2. Warm restart count on the CPE is 2, not nominal. Later investigation showed that it occurred only at startup near launch time. TLM data dump directory has some day 204:16:01:54 - 204:19:07 data created in April. Attempt will be made to delete these data during an LOS. See flt note 048. EGSE TLM dropout. These dropouts continue. We suggest that Dan Leonard's patch be tested using squirt backup server and a laptop with HRC software. A good time would be perhaps during Earth Scan 4, 206:16:40-18:00, i.e. Sunday, 12:40-2:00 pm EDT. Tom is working to coordinate this with the rest of the Chandra OPS team. 205:20:41 - Go to FMT2 for ACIS FP temp measuring. Result: -118.9C. Temperature ~20:35 PCAD just learned that there is a temperature dependence of the ESA calibration, of as yet unknown magnitude. 20:56 Primary battery heater did not come on as needed earlier. Redundant heater came on now. TST will recycle the relay on primary heater, see CAP 046. 21:07 good oxidizer activation. 21:42 change obsid to 62496. ~23:00 PCAD's preliminary gyro bias report: the yaw result differs on the descending leg data vs the ascending leg. The difference is ~= 0.25 degree/day. 206:01:11 IPS burn #1 - went very well. Attitude control prior to and during the burn was RCS, which has a ~4 degree deadband. Tom plotted RA, dec & roll from the quaternion thru the burn. We saw it drifting in the dead band, hitting the edge in RA at 192 and rebounding~ 1 degree. Then the burn started, and RA jumped from 193 to 200 and then drove back to 196 under RCS control, for a rough average value of 197, only 1 degree off the middle of the dead band. Dec hit the edge of its band at 2.5 before the burn, drove back 1 degree, jumped from 2 to -1 and then drove back to ~0, for an average of ~ 0.5, or 0.25 from the middle of its band. A rough average, combining RA and dec in quadrature gives 1 degree pointing error during the burn. ~03:05 ACIS FP reading -118.9 again. Actions in the pipe: * fix the EGSE dropout problem * re-do the HRC-S pulser test * watch ACIS FP temperature and find a stable setpoint