To:sot_shift
from: Dan Schwartz
date: 2 Aug 99, 0825 EDT
Subject: SOT shift report, Shift A11
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See http://asc.harvard.edu/acis/SOT_reports/sot-shift.html, or 
/proj/ascwww/AXAF/extra/science/htdocs/acis/SOT_reports/July_30_1999_B.txt.

Shift A11. 
	Start at 214:01:00  GMT
		 = 0900 pm 1 Aug
	End	    9:20am 2 Aug
   
SOT Lead	DAS
Spac/Aspect	RAC
FOT/Sci liason	EM
HRC		MJ,GA,SSM,GM
ACIS 		PPP,RB,ES,MP

(Times will be given in GMT on day 214. In general
times are rough, not precise.)

PLAN
set up acis event histogram
HRC I checkout activities
Pick up with normal sun mode demo
Replan radiation safing time, scs 129, due to change in 
   expected orbit associated with not doing IPS-4 burn. 
Facility power outage planned for 0700 -- 1000 GMT. 
Perform normal sun mode demo.

EVENTS
ran CAP 129 for fid light re-acquisition.

ran cap 102, select iru B in low range.

Vacuum monitor on and reading 9.7 x 10^-6 throughout the shift.

02:17 obsid 62956. Change to format 2, setup for event histogram 02:30.

02:48 proceed with HRC antico shield 1 ON. Change to format 1.
HRC-I results are the same as previously: same high rates
at voltage steps less than operational, up to step 10.  Will terminate and
shut down HRC HV at 03:51.

SO we will NOT use OBSID's 62955 or 62954 tonight.
Return to format 2, about 04:05.

We will now Run the three standard ACIS internal calibration
runs, for about 2hr20min each, until ~1300. Will use
OBSID's 62735,62734,62733, 
and will NOT use OBSID 62732. 
Start 62735 at 04:54.  Stop science at 07:40.
Start 62734 at 07:42.  Stop science at 10:25
Start 62733 at 10:26.  

SSR playback, 05:33.

Maneuver to 107 deg pitch, for stray light diagnosis. 
 
Normal sun mode demo at 07:45. Maneuver 25 deg off sun normal,
then return at 08:16.

Run CAP 91a to reacquire 4 fid lights at brightest level, 12:15.


NOTES/ISSUES/PROBLEMS
Anomalous fid light acquisition behaviour. Get 3 lights 
in the expected windows, 7,6,5, but the 4th light
is acquired in window #0. This means it is overwritten
with a monitor window, which is commanded for slots 
3,2,1,0. So we only are tracking 3 fid lights. Original 
thought was that this was associated with stray light, but
a test pitching off 17 deg where there is no stray light ended up
with the same results of fids acquired in slots 7,6,5, and 0.
Resetting the PEA cleared up this problem.  

We have previously noted that the apparent magnitude reported
by the ACA to the OBC seems to be based on the actual number
of counts in the star/fid window, and NOT on the background
subtracted number of counts. This implies that if the 
background level raises substantially, the star magnitude is 
reported spuriously bright. Because the OBC imposes a magnitude
window on acceptible stars, it is possible that the star, or fid
light, will NOT be tracked if the background level rises 
substantially. 

The IPS-4 burn was not done. This was due to uncertainties about
the LAE-3 performance during the IPS-3 burn, which caused a 
desire to switch to LAE-2 and LAE-4 for IPS-4. This switch
requires extensive software patching, plus an extra short
burn to characterize the LAEs prior to the final burn. So
IPS-4 will be the characterization burn, in about 60 hours, 
followed by IPS-5 burn to final orbit 60 hours later. We need 
to replan science activities for this new scenario.

Issued flight note 176 by Rob Cameron plotting the stray 
light in the ACA monitor windows as a function of pitch angle.
It shows that at the specified angle of 107 the ACA is free
of stray light, so that this angle is adequate for ACA 
calibrations with the SSD closed. The data probably indicates 
no stray light as near as 100 deg to the sun.

-------------------------------------------------------
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 
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