Sep_03_1999_M44.txt Shift M44
        Start at 1999:246:18:00:00 GMT
                = 1999 Sep 03  2:00pm EDT
        End       1999 Sep 03 10:00pm EDT

   
SOT Lead	Bill Podgorski
SOT SC/ACA	
FOT-SI		
HRC-SI          Steve Murray/Gerry Austin
ACIS-SI		Yousef Butt/Paul Plucinsky

Plan: Run P10 HRC observations:

      - Complete 9000 sec observation of CAS-A as part of "standard candles"
      - Perform HETG software insertion/retraction testing via CAP 371
        while in radiation zone


      
EVENTS							    DONE	OBSID
--------------						    ----	-----
Start Shift                                             246:1800          171
----- Out of Contact------
Running HRC-I observation 171                               ongo
AOS DSS61                                               246:1800
----- Real time------ 
End HRC-I 171                                           246:1805
Execute Rad zone entry ATS                              246:1805
Start CAP 371 to test S/W insertion/retraction of HETG  246:1900
  (see discussion below)


End of shift                                            247:0200

NOTES/ISSUES/PROBLEMS 
--------------------- 

1) CAP 371 was planned to test software insertion and retraction of
   the HETG. The initial insertion failed due to there being incorrect 
   state flags in the OBC. These flags were incorrect due to the failed 
   previous attempt to insert the HETG via software. These flags were
   corrected via real-time commands and the software insertion of the
   HETG via SCS 247 was successful. 

   During the insertion, however, it was noticed that the telescope MCE-B
   (Mechanism Control Electronics-B) 28 volt motor drive voltage telemetry
   monitor was reading about 6.2 volts during grating motion, even though the
   motor was being driven by MCE-A. We expected the MCE-B drive voltage
   to be zero. Investigation of prior HETG flight insertions and retractions
   indicated that this voltage was present in every case (total of 5, 3
   insertions and 2 retractions). 

   It was decided to defer retraction of the HETG until the 0300-0400 COMM period 
   while the problem was analyzed. A telecon was held at 6:00pm EDT to
   discuss the issue.

   Several possible causes of the problem have been identified. The most
   likely cause is that the voltage seen is due to back EMF generated 
   on the B side (redundant) windings as the A-side windings are driving
   the motor. Both the A and B side windings are on a common shaft, hence
   there will be some voltage generated as the motor shaft rotates. The 
   voltage level to be expected is unknown at this time. Kodak and TRW
   were tasked to look into this via both circuit analysis and test, using
   flight spares at TRW. 

   A second possibility could be a short between the A and B side windings.
   This could be a more serious issue. 

   A decision was made to retract the HETG during the day 247 0300-0400 (tonight)
   comm period, using the A side MCE. There will be another telecon to
   discuss the issue at 4:00pm EDT tomorrow (Saturday, Sept 4). The
   meet-me number will be posted on 617-496-7030. 
   
   

2) Planned COMM:    246:1800 --> 246:2300   DSS61
                    247:0300 --> 247:0400   DSS16 (Retract HETG)
                    247:0845 --> 247:1030   DSS42 (Upload P11)
                    247:1815 --> 248:0220   DSS61
                    248:0215 --> 248:0415   DSS24
                    248:1030 --> 248:1215   DSS42
                    248:1600 --> 248:1800   DSS66
                    248:2200 --> 249:0330   DSS61 (Insert LETG)

3) Radiation Zone:  246:1830 --> 247:0523

4) Perigee:         247:0007

5) P11 Load: To be put out for general review at about 9:30pm.