chandra x-ray observatory cxc acis ops team march 27, 2008 1 controlling the acis fp temperature:...

Chandra X-Ray Observatory CXC

ACIS Ops team March 27, 20081

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

Turn Off the ACIS DH HeaterTurn Off the ACIS DH Heater

ACIS Ops TeamACIS Ops Team



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 in a 110 ks observation

Change to Standard Operations• turn off the ACIS DH heater as the new standard configuration

What Are We Asking For Today ?

Preparation for New Configuration

• CXC DS has implemented a new algorithm to correct aspect when the ACIS camera body temperature is fluctuating and the Fid Lights are moving

Approval today is contingent upon a successful deployment of the new SW by the CXC DS, ie: ACIS Ops will not turn off the DH heater until the DS gives the OK



ACIS FP Temperature over the MissionACIS FP Temperature over the MissionBissell (NGST), 8 hr averages of FP temperature, 30 day running average

Review from Sep 6, 2007 FDB Presentation: Why Are We Doing This ?



ACIS FP Temperature over the MissionACIS FP Temperature over the Mission

Grant

(MIT)



ACIS Gain vs. FP TemperatureACIS Gain vs. FP Temperature

Grant (MIT)

0.3% is the budget for the gain calibration,

0.5 C increase in FP temperature results in gain being out of the calibration specification



ACIS FWHM vs. FP TemperatureACIS FWHM vs. FP Temperature

Grant (MIT)

FWHM of FI CCDs is a sensitive function of FP temperature



ACIS FP Temperature over the MissionACIS FP Temperature over the Mission

Grant

(MIT)



Expected Improvement with the DH Heater off

• Joe Vogrin’s and Neil Tice’s analysis indicates that the FP temperature could be up to 3 degrees colder if BOTH the ACIS DH heater and the SIM FA6 heater are off

• In Vogrin’s final analysis, he modeled a range of pitch angles from 45 to 172 degrees and the SIM at the ACIS and HRC positions, for the default heater configuration and for the DH heater and SIM FA6 heaters both off configuration

• In his initial analysis for a pitch angle of 155, Vogrin modeled the effect of turning off the heaters separately. For that case, he found that turning off the DH heater reduced the ACIS FP temperature by 1.1 deg, turning off the SIM FA6 heater reduced it by 0.4 deg, and turning off both the DH heater and SIM FA6 heater reduced it by 2.6 deg. Therefore, the reduction in the FP temperature by turning off both heaters is larger than the sum of the reductions of turning the heaters independently.

• In the intial analysis, Joe predicted that the 1CBAT would drop to -66/-67 C. We know from our tests that 1CBAT gets as cold as -69.8 C for a pitch angle of 155 degrees, so we would expect more than 1.1 deg decrease in the FP temperature for this orientation from the DH heater alone being off



Summary of DH Heater offSummary of DH Heater offTests at Rear-Sun:Tests at Rear-Sun:Minimum T achieved is -69.8 CFull results available at:cxc.harvard.edu/twiki/bin/view.cgi/AcisOps/CoolingTests

Date Pitch SIM Duration (ks) Min 1CBAT (C) Min 1CBBT (C)2007:259 128.9 HRC-S 37.14 -69.75 -69.752007:265 121.8 ACIS-I 38.4 -67.29 -67.29 2007:290 132.14 ACIS-I 54.3 -67.29 -67.292007:292 132.77 ACIS-I 111.58 -69.75 -67.292007:295 133.43 ACIS-I 82.86 -67.29 -67.292007:297 133.86 ACIS-I 112.25 -69.75 -67.292007:300 134.27 ACIS-I 105.79 -69.75 -67.292007:303 134.61 ACIS-I 30.13 -67.29 -64.832007:305 134.73 ACIS-I 137.06 -69.75 -69.752007:308 134.79 ACIS-I 107.77 -69.75 -67.292007:323 165-151 HRC-S 51.63 -69.75 -69.752008:013 153 HRC-S 59.79 -69.75 -69.752008:021 155 HRC-S 58.25 -69.75 -67.292008:024 153 HRC-S 53.34 -69.75 -69.752008:029 154 HRC-S 57.68 -69.75 -69.752008:032 154 HRC-S 52.42 -67.29 -67.29

Date A Tau Cool (ks) A Tf Cool (C) B Tau Cool (ks) B Tf Cool (C)2007:259 30.09 [19.52,62.92] -73.33 [-80.33,-71.09] 23.27 [15.87,42.07] -70.85 [-74.61,-69.33]2007:265 17.68 [12.65,27.98] -68.51 [-70.10,-67.69] 27.06 [17.36,57.26] -69.83 [-74.96,-68.15] 2007:290 20.67 [15.68,29.18] -68.09 [-68.96,-67.55] 37.33 [23.94,79.99] -69.36 [-74.01,-67.89]2007:292 52.69 [39.54,76.18] -70.36 [-71.62,-69.65] 16.48 [14.34,19.03] -67.42 [-67.33,-67.52]2007:295 15.78 [13.26,19.00] -67.50 [-67.73,-67.29] 24.04 [19.82,29.84] -67.75 [-68.17,-67.42]2007:297 49.03 [36.62,71.08] -70.12 [-71.26,-69.48] 14.44 [12.59,16.62] -67.40 [-67.54,-67.26]2007:300 47.22 [36.74,64.34] -70.46 [-71.49,-69.82] 15.28 [13.31,17.62] -67.42 [-67.58,-67.27]2007:303 8.1[5.32,14.41] -65.16[-65.86,-64.75] 9.98[6.79,16.68] -65.38[-66.34,-64.81]2007:305 50.73[42.20,62.52] -70.35[-70.90,-69.95] 15.35[13.49,17.50] -67.42[-67.53,-67.28]2007:308 32.39[24.77,44.88] -69.00[-69.63,-68.61] 15.38[13.40,17.73] -67.42[-67.58,-67.26]2007:323 24.96[19.60,33.71] -71.41[-72.78,-70.54] 27.36[20.29,40.98] -70.74[-72.78,-69.66]2008:013 27.04[22.86,31.88] -69.49[-69.88,-69.11] 49.97[43.66,57.03] -71.32[-71.70,-70.91]2008:021 8.62[7.36,10.15] -67.63[-67.87,-67.41] 10.36[8.93,12.11] -67.47[-67.73,-67.24]2008:024 29.86[25.32,35.09] -69.61[-70.0,-69.22] 43.82[37.08,51.43] -70.72[-71.15,-70.26]2008:029 25.57[21.61,30.21] -69.42[-69.81,-69.04] 38.43[32.01,45.25] -70.97[-71.46,-70.42]2008:032 16.31[13.63,19.97] -67.31[-67.62,-67.04] 33.69[26.84,41.33] -68.52[-71.46,-70.42]



Summary of DH Heater Off Tests at Rear/Forward SunSummary of DH Heater Off Tests at Rear/Forward Sun

Date Pitch SIM Duration (ks) Min 1CBAT (C) Min 1CBBT (C)2008:034 154; 65 HRC-S;ACIS-I 111.22 -69.75 -69.752008:037 154; 65; 55 HRC-[S/I]; ACIS-S 170.72 -72.2 -72.2

Date A Tau Cool (ks) A Tf Cool (C) B Tau Cool (ks) B Tf Cool (C)2008:034 31.51 [28.27,35.27] -70.02 [-70.26,-69.80] 44.09 [39.21,49.58] -71.09 [-71.44,-70.74] 2008:037 53.08 [47.96,59.17] -72.32 [-72.66,-72.04] 54.48 [49.61,60.18] -72.22 [-72.56,-71.92]

During second test, the Camera Body temperature reached -72.2 C on side A and B for the first time in the mission.



DePasquale (SAO),

min temperature

-69.8 side A/B

~63 ks at tail-Sun

~48 ks at forward-Sun

Cool ACIS DH for an Entire Perigee Passage and during E0102 observations

Results of the 4/5 Feb 2008 Test



DePasquale (SAO)

Colder Camera Body results in a colder FP temperature

Results of the 4/5 Feb 2008 Test FP Temperature during the test



DePasquale (SAO)

Min temperature -72.2 C

~59 ks at tail-Sun

~110 ks at forward-Sun

Evidence the primary survival heater turned on

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)

Results of the 6/7 Feb 2008 Test FP Temperature during the test



DePasquale (SAO)

1CBAT during the end of the 6/7 Feb 2008 Test

1CBAT goes from -72.2 C to

-69.8 C every 3ks



DePasquale (SAO)

More than one sample in first case but only one sample in the second case

Zoom of the First Two Instances in which 1CBAT increased to -69.8 C



DePasquale (SAO)

Table of Instances in which 1CBAT increased to -69.8 C

Tick# Time(DOY 39+) Time(ks) #samples Diff(ks)1 0.2171-2179 136.0521-136.1013 2 0.0 2 0.2551-2553 139.3321-139.3485 1 3.233 0.2885-2891 142.2185-142.2677 2 2.874 0.3208-3213 145.0065-145.0557 2 2.735 0.3527-3528 147.7617-147.7781 1 2.716 0.3826-3832 150.3529-150.4021 2 2.607 0.4142-4147 153.0753-153.1245 2 2.678 0.4441-4447 155.6665-155.7157 2 2.549 0.4726-4728 158.1265-158.1429 1 2.4110 0.5003-5009 160.5209-160.5701 2 2.3811 0.5292-5298 163.0137-163.0629 2 2.4412 0.5577-5578 165.4737-165.4901 1 2.4113 0.5854-5859 167.8681-167.9173 2 2.38



Location of 1CBAT and Survival Heater

and SSTS

Tice (LMA)



ACIS Detector Housing Survival Heater Geometry

•HR7, HR8: 22 W @ 29 V• Prime survival -71.1 °C• Rdnt survival -73.6 °C• RT7 & RT8 are SSTS

•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)



Did the Survival Heater Come on ?

• Regular cycles of 1CBAT up to -69.8 C every 3 ks are consistent with the survival heater cycling on and off

• Cycling between -72.2 C and -69.8 C is consistent with setpoint of primary survival heater of -71.1 C

• more frequent cycles up of 1CBAT than 1CBBT are consistent with survival turning on and off since survival heater is on side A

• more than one consecutive reading of 1CBAT at -69.8 C is consistent with the survival heater turning on as opposed to 1CBAT drifting slowly down to -72.2 C with occasional single ticks up to -69.8 C

• Neil Tice adds, “The frequency of oscillation (1 cycle per 40 minutes) in 1CBAT is consistent with the thermal time constant of the DH along with a 22 W short duration (few minutes) heat pulse,”

Conclusion• It is likely that the primary survival heater did turn on

• All ACIS components and the Fid Lights operated nominally with the camera body at -72.2 C

• It is safe to turn off the DH heater for any spacecraft orientation and for the foreseeable future



Implementation: Commanding-- realtime commanding preferred to maintain flexibility

-- very simple, CAP 1062 under development which issues two ACIS HW commands to turn off and to disable the heater “1HHTRBOF’’ and “1HHTRBDS”

-- contingency CAP 1063 under development to turn on the DH side B heater in case the Camera Body gets too cold, issues two ACIS HW commands to turn the heater on “1HHTRBEN’’ and “1HHTRBON’’

Status of CXC DS SW Update

• The DS7.6.11.6 release of CXCDS processing contains new aspect pipeline code that uses fid light and ACIS temperature telemetry to compensate for thermal contraction of the fid light mount as the DH temperature varies.• This has been verified by processing all ACIS DH test obsids as well as two HRC observations.• Detailed inspection of pipeline outputs showed the expected behavior of the correction code. Nominal aspect performance was recovered.



Schedule for Implementation

• ACIS Ops waits for final approval from DS that SW has been deployed and is functioning as expected• ACIS Ops schedules final CAP review to approve time of CAP execution• We prefer to execute this during a perigee passage to minimize the temperature fluctuations during a science observation• Earliest anticipated date of execution is Monday April 7th, perigee passage on that day which we could use• Need to coordinate with MP, current plan is to not include any ACIS DH heater commands in the APR0708 load

chandra x-ray observatory cxc acis ops team march 27, 2008 1 controlling the acis fp temperature:...

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