Controlling the ACIS FP Temperature:

1
Controlling the ACIS FP Temperature Results
from the First Two Tests
ACIS Ops Team
2
First ACIS DH Cooling Test Perigee Passage
ACIS FP Temperature
DePasquale (SAO)
Begin
End
3
First ACIS DH Cooling Test Perigee Passage
DePasquale (SAO), Vogrin predicts a steady state
temperature of -69 to -71 C at the HRC position
and pitch angle of 150
Begin
End
4
First ACIS DH Cooling Test Heating
DePasquale (SAO), commanded by SOP_61014_DAHTR_B_O
N
5
Second ACIS DH Cooling Test OBSID 9593 CDF-S
DePasquale (SAO)
Begin
End
6
Second ACIS DH Cooling Test OBSID 9593 CDF-S
DePasquale (SAO), Vogrin predicts a steady-state
temperature of -68 to -70 C at the ACIS
position and a pitch angle of 120
Begin
End
7
Second ACIS DH Cooling Test Heating
DePasquale (SAO), commanded in the load
8
What Have We Learned ?

• The side B heater can be turned off and turned
  back on
• The commands/script in SOP_61014_DAHTR_B_ON
  worked as expected
• The commands in the load worked as expected
• The time constant for cooling is shorter than
  expected (25-30 ks), this means that it is
  possible that the camera body temperatures
  (1CBABT) could reach the point at which the
  survival heaters will turn on (primary -71.1 C,
  redundant -73.6 C) if the camera body is allowed
  to cool long enough and the spacecraft
  orientation permits
• Asymptotic temperatures determined from the fits
  are consistent with Vogrins predictions
• The DH heater will draw 55-60 W when turned on
  for a short amount of time.
• It takes the DH about 1 hr to get back to the
  nominal operating temperature of 1CBAT/1CBBT
  -62.4 C/-59.9 C

9
New Proposed Tests

• Conduct one test per week in upcoming CDF-S
  observations, there are CDF-S observations in the
  OCT1507, OCT2207, OCT2907, NOV0507, and NOV1207
  weeks
• -- pitch angles vary between 130 and 135
• -- model predicts that 1CBABT should
  not drop below -68/-66 C
• -- exposures vary from 28 ks to 160 ks
  (subject to change of course), we would select
  observations around 80 ks
• -- commanding in the load, with
  monitoring by ACIS Ops and CC/OC

Possible Future Tests

• Turn off the side B DH heater for perigee
  passages
• -- the HRC position is a colder
  orientation for the camera body, temperature
  might drop to the point at which the survival
  heaters would come on
• -- the CTI measurements would benefit
  from a colder camera body since the FP
  temperature would be colder
• -- we need to be comfortable with
  relying on the survival heaters to turn on at
  -71.1 C and then off again at -69.8 C
• -- we would like to come back to an FDB
  meeting in the future after we have thought about
  this more

10
ACIS Detector Housing Survival Heater Geometry
Trinh(NGST)

• HR7, HR8 22 W _at_ 29 V
• Prime survival -71.1 C
• Rdnt survival -73.6 C
• Better than 1.19 C accuracy (_at_ -70 C ) for
  1YA94 SSTS that controls survival heater
• Located on Z face of Detector Housing (side A,
  1CBAT)
• Closest telemetry thermistor is 1CBAT (FM07)