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Controlling the ACIS FP Temperature: Turning off the DH Heater During Perigee Passages

Controlling the ACIS FP Temperature: Turning off the DH Heater During Perigee Passages ACIS Ops Team. New Proposed Test. turn off the DH heater for an entire perigee passage monitor the Camera Body side A/B temperatures (1CB[AB]T)

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Controlling the ACIS FP Temperature: Turning off the DH Heater During Perigee Passages

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  1. Controlling the ACIS FP Temperature: Turning off the DH Heater During Perigee Passages ACIS Ops Team

  2. New Proposed Test • turn off the DH heater for an entire perigee passage • monitor the Camera Body side A/B temperatures (1CB[AB]T) • If both side A and B read -72.2 C or colder, contingency response is to turn the DH heater back on Success Criteria • The Camera Body side A (1CBAT) -72.2 C and side B (1CBBT) -72.2 C for the duration of the test Change to Standard Operations If the test above is successful: • turn off the DH heater for all perigee passages for which the pitch angle is larger than 140 degrees

  3. Summary of DH Cooling Tests Minimum Temperatures and Fit Results

  4. Summary of DH Cooling Tests • proposed test is most similar to the first test and NOT like the other tests during the CDF-S observations in which the SIM is at the ACIS position • first test resulted in a minimum temperature of -69.8 C for both 1CBAT and 1CBBT in 37 ks • extrapolation of first test predicts temperatures of 1CBAT=-71.6 C and 1CBBT=-70.0 C after 56 ks • 90% CL on asymptotic temperatures is 1CBAT=-80.3 C and 1CBBT=-74.6 C • primary survival heater should turn on at -71.1 C and secondary survival heater should turn on at -73.6 C

  5. How fast can the Camera Body get cold ? 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 End Begin

  6. How fast can the Camera Body get cold ? First ACIS DH Cooling Test: Perigee Passage Side B temperature, 1CBBT End Begin

  7. How fast does the Camera Body warm ? First ACIS DH Cooling Test: Heating DePasquale (SAO), commanded by SOP_61014_DAHTR_B_ON DH heater draws a maximum of 60 W, survival heaters draw 22 W If the survival heater turns on, side A should respond faster than side B

  8. Detector Housing Survival Heater Geometry Trinh(NGST) • 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)

  9. One Concern The ACIS Camera Body and the Fid Lights get colder than -72.2 C. Fid Lights should not be allowed to drop below -76.0 C. How could this happen ? • DH cools faster than predicted from earlier test • primary survival heater fails to turn on and/or secondary survival heater fails to turn on • thermostat for primary survival heater turns on at a temperature less than -71.1 C (how close are the temperatures read out by 1CB[AB]T and the survival heaters ?) • SCS 107 interrupts the load before the command to turn the DH heater back on is executed and one of the above is true

  10. Implementation -- DH heater will be commanded on and off in the load (has been executed 6 times in the load) -- realtime COMs will be provided to monitor the Camera Body temperature during the second half of the perigee passage. FOT MP has identified COMs on DOY 2007:323 (Monday 19 November 2007) -- contingency CAP to execute SOP_61014_DAHTR_B_ON will be ready to run Time Elapsed Time Event 323:07:00 0.0 DH side B heater is turned off by the load 323:13:10 15000 s AOS, verify heater is off 323:14:10 18600 s LOS 323:15:45 31500 s AOS, verify temperatures 323:16:45 35100 s LOS 323:21:15 51300 s AOS, verify temperatures 323:22:40 56400 s side B heater turned on by the load 323:23:10 58200 s LOS

  11. Telemetry Verification Camera Body temperature 1CBAT/1CBBT digitization is ~2.47 C 1CB[AB]T -71.1 C, primary survival heater set point -73.8 C, secondary survival heater set point -76.0 C, must not drop below • side A (1CBAT) cools faster than side B (1CBBT) • side B (1CBBT) warms faster than side A when the DH heater is used • side A (1CBAT) should warm faster when the survival heater is used

  12. Telemetry Verification Five possible cases: 1CBAT > -72.2 C and 1CBBT > -72.2 C -- allow test to proceed 1CBAT = -72.2 C and 1CBBT > -72.2 C -- allow test to proceed 1CBAT > -72.2 C and 1CBBT = -72.2 C -- allow test to proceed 1CBAT = -72.2 C and 1CBBT = -72.2 C -- terminate test 1CBAT < -72.2 C and 1CBBT < -72.2 C -- terminate test

  13. Turn the DH Heater Off for Future Perigee Passages • Keeping the Camera Body colder will keep the FP temperature colder • If the proposed test is successful, we want to turn off the DH heater for all perigee passages for which the pitch angle is greater than 140 degrees Limit Changes Mnemonic Current Yellow Low New Yellow Low Current Red Low New Red Low 1CB[AB]T -70.5 C -72.2 C -75.5 C -74.7 C Camera Body Temp 1DAHBCU 0.80 A 0.0 A 0.20 A 0.0 A DA Htr Current B 1DAHBVO 10.5 V 0.0 V 3.5 V 0.0 V DA Htr Voltage B 1DAHHBVO 25.0 V 0.0 V N/A/ N/A DA Htr Input Voltage B 1DAHTBEN Enb N/A DA Htr B Enb/Dis 1DAHTBON On N/A DA Htr B On/Off

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