To:sot_shift
from: Dan Schwartz
date: 26 July 99, 0900 EDT
Subject: SOT shift report, Shift A4
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Shift A4. 
	Start at 207:03:30  GMT
		 = 11:30pm 25 July 99
	End	    9:49am 26 July
   
SOT Lead	DAS
Spac/Aspect	RAC
FOT/Sci liason	EM
HRC		SSM,JG,JC
ACIS 		PPP,RB,SV
(Times will be given in GMT on day 207. In general
times are rough, not precise.)


PLAN
Turn on vacuum monitor and measure pressure.
Monitor ACIS focal plane temperature.
Commission EPHIN. Perform Trigger test. 
Prepare for Earth Scan #5, start scan.
Participate in replanning Transfer Orbit events.

EVENTS
Turn on vacuum monitor at ~0410. Pressure creeps up to
a steady 10^-4 after about an hour warmup. This is slightly
lower than yesterday. Turn off monitor ~0520.

Format 2 at 0418: ACIS focal plane temperature = -118.9 C
Format 2 at 0902: ACIS focal plane temp        = -118.9
Format 2 at 0954: ACIS focal plane temp	       = -118.9

EPHIN commissioning sequence starting ~0430. Complete ~0815.
RADMON enabled, 0850. 
EHPHIN trigger test: ACIS successfully receives High RAD and
Low RAD flags, 0920. HRC radiation flag tests also pass, 0935.
So the EPHIN now will be left on. It is fully operational
and is taking REAL SCIENCE DATA!!


Make an attitude and bias correction update. Upload ~0720.
These are relatively small corrections. Largest updates
were 0.3 deg/day in roll and 1/2 deg in YAW.

SSR dump starts ~0930.

LGA swap at 1210.

~1234, end maneuver, start earth scan 5.

NOTES/ISSUES/PROBLEMS
The difference between the ACIS focal plane temperature and its
set point is now interpreted in terms of the residual gas in
the detector volume. This gas could conduct heat from the 
detector housing, which is held at -60 C, to the focal plane.
It is predicted that after opening the Big vent valve that the
focal plane temperature will reduce to exactly the set point. 
We will still plan to lower the set point, as discussed in 
flight note #66, to confirm active control of the focal plane.
We will repeat every, say, 6 months throughout the mission
to monitor any potential degradation (which we do not
expect, according to design and analysis) in the ability of the 
radiators to control the focal temperature.

Report on IPS burn #2: new apogee 72068.68 km,
perigee 3435.08 km, within 13 km of nominal values.

Replan of next 36 hours starts ACIS partial bakeout and big
valve opening 2 hours earlier, and moves HRC-S pulse
inject repeat to PET 03/20 during ACIS cooldown.

LOOK AHEAD Issues: At PET 3/21 we need to be sure that 
   ACIS has cooled below -110C before allowing maneuvers.
	During ACIS CCD Checkout following 04/08 we need 
to work closely with TST lead to uplink frequent new 
OBSID's, one for each science run. 

At ~1240 we notice SCS 84, ACIS exit from radiation, has
triggered. It is reasonable that 83 (enter radiation) was
called by RADMON, but why 84??  Safing and Software must
diagnose.

-------------------------------------------------------
Dan Schwartz,	MS #3
das@head-cfa.harvard.edu  
phone: (617)495-7232    FAX:   (617)495-7356
cell phone: (617)512-5627   
pager: 800-759-8352 PIN 1636502
       or e-mail 1636502@skytel.com 
-------------------------------------------------------