Controlling the ACIS FP Temperature:

1

• Controlling the ACIS FP Temperature
• Turning off the DH Heater During ALL Perigee
  Passages
• ACIS Ops Team

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What Are We Asking For Today ?
Change to Standard Operations

• turn off the DH heater for ALL perigee passages
  regardless of pitch angle

Results of Tests in FEB0408 Load

• two tests conducted during the FEB0408 load
  demonstrated that it is safe to turn off the DH
  heater at forward-Sun orientations, the Camera
  Body temperatures never dropped below -72.2 C

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Results of the 4/5 Feb 2008 Test
Cool ACIS DH for an Entire Perigee Passage and
during E0102 observations
DePasquale (SAO), min temperature -69.8 side
A/B 63 ks at tail-Sun 48 ks at forward-Sun
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Results of the 4/5 Feb 2008 Test
FP Temperature during the test
DePasquale (SAO) Colder Camera Body results in a
colder FP temperature
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Results of the 6/7 Feb 2008 Test
Cool ACIS DH for an Entire Perigee Passage, some
E0102 observations and some HRC observations
DePasquale (SAO) Min temperature -72.2 C 59 ks
at tail-Sun 110 ks at forward-Sun Some evidence
the primary survival heater turned on
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Results of the 6/7 Feb 2008 Test
FP Temperature during the test
DePasquale (SAO)
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Summary and Conclusions of Tests at Forward-Sun

• 1CBAT and 1CBBT reached a minimum temperature of
  -69.8 C in the first test after 48 ks at
  forward-Sun and -72.2 C in the second test after
  110 ks at forward-Sun (in both cases after
  cooling for the entire perigee passage at
  tail-Sun)
• time constants at forward-Sun orientations are
  very similar to those in tail-Sun orientations
• minimum temperature of -72.2 C at forward-Sun is
  consistent with Vogrins model
• ACIS Fid lights are operating nominally after
  these tests
• it is safe to turn off the DH heater for an
  entire perigee passage at any pitch angle
• a cold Camera Body keeps the FP colder in
  general and allows a faster recovery after
  perigee passage

Future Plans

• we plan to come back to the FDB to ask for
  approval to turn off the DH heater for good and
  we will discuss the issue of the primary survival
  heater
• waiting for DS to update schedule on release of
  SW which accounts for a variable Camera Body
  temperature