chandra x-ray observatory cxc acis ops team september 27, 2007 1 controlling the acis fp...

Chandra X-Ray Observatory CXC

ACIS Ops team September 27, 20071

Controlling the ACIS FP Controlling the ACIS FP Temperature: Temperature:

Results from the First Two TestsResults from the First Two Tests

ACIS Ops TeamACIS Ops Team



ACIS FP TemperatureACIS FP Temperature

DePasquale (SAO)

First ACIS DH Cooling Test: Perigee Passage

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DePasquale (SAO), Vogrin predicts a steady state temperature of -69 to -71 C at the HRC position and pitch angle of ~150

First ACIS DH Cooling Test: Perigee Passage

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DePasquale (SAO), commanded by SOP_61014_DAHTR_B_ON

First ACIS DH Cooling Test: Heating



DePasquale (SAO)

Second ACIS DH Cooling Test: OBSID 9593 CDF-S

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DePasquale (SAO), Vogrin predicts a steady-state temperature of -68 to -70 C at the ACIS position and a pitch angle of ~120

Second ACIS DH Cooling Test: OBSID 9593 CDF-S

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DePasquale (SAO), commanded in the load

Second ACIS DH Cooling Test: Heating



What Have We Learned ?What Have We Learned ?

1) The side B heater can be turned off and turned back on

2) The commands/script in SOP_61014_DAHTR_B_ON worked as expected

3) The commands in the load worked as expected

4) The time constant for cooling is shorter than expected (25-30 ks), this means that it is possible that the camera body temperatures (1CB[AB]T) 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

5) Asymptotic temperatures determined from the fits are consistent with Vogrin’s predictions

6) The DH heater will draw 55-60 W when turned on for a short amount of time.

7) It takes the DH about 1 hr to get back to the nominal operating temperature of 1CBAT/1CBBT -62.4 C/-59.9 C



New Proposed Tests1) 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 1CB[AB]T 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 Tests1) 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



ACIS Detector Housing Survival Heater Geometry

•HR7, HR8: 22 W @ 29 V• Prime survival -71.1 °C• Rdnt survival -73.6 °C

•Better than 1.19 °C accuracy (@ -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)

Heater description

Pr or Red

Htr Bus

Enable Cmd

Disable Cmd

Heater Flight Telemetry Mnemonic

Heater Power at 29 volts (watts)

Heater Resistance (ohms)

Heater Close Set Point Temp (°C)

Heater Open Set Point Temp (°C)

Primary Heater Monitor Thermistor Mnemonic

Backup Heater Monitor Thermistor Mnemonic

ACIS Det. Hsg. Survival

PR 2 NA NA NA 22 38.2 -71.1 -69.8 1CBAT 1CBBT

ACIS Det. Hsg. Survival

RD 7 NA NA NA 22 38.2 -73.6 -72.5 1CBAT 1CBBT

Trinh(NGST)

chandra x-ray observatory cxc acis ops team september 27, 2007 1 controlling the acis fp...

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