1. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 1 Update on a Proposed Bakeout CXC SOT & FOT, ACIS Instrument Team and CXC SOT & FOT, ACIS Instrument Team and MSFC Project Science MSFC Project Science

2. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 2 New Items since Last CUC Briefing (January 2005) MIT/ACIS team conducted irradiation tests of flight spare CCDs at GSFC in May 2005. MIT/ACIS concluded that the CTI increase from another +30 C Bakeout would most likely be smaller than previously believed, ~5%. MSFC Project Science continued to explore the sensitivity of the simulation results to the parameters (ie: temperatures of the relevant surfaces, volatility of the contaminant) The ACIS contamination working group reviewed the new results in the summer and decided on July 15, 2005 against recommending a Bakeout. The team felt that the uncertainties were too large to be able to predict the outcome of the Bakeout with any confidence. The Bakeout is therefore postponed indefinitely.

3. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 3 Docosane, nominal T OBF : Mass column 1: ACIS OBF 2: Camera top 3: ACIS snoot 4: ACIS collimator 5: SIM trans table 6: SIM focus struc 7: OBA stove pipe 8: Optical bench 9: OBA vent 1 dy1 wk1 mo5 yr1 yr  = 0.30 O’Dell & Swartz (MSFC)

4. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 4 Docosane, de-rated T OBF : Mass column 1: ACIS OBF 2: Camera top 3: ACIS snoot 4: ACIS collimator 5: SIM trans table 6: SIM focus struc 7: OBA stove pipe 8: Optical bench 9: OBA vent 1 dy1 wk1 mo5 yr1 yr  = 0.30 O’Dell & Swartz (MSFC)

5. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 5 Min to vent 0.2 g in 1 orb: 5  10 -3  g cm -2 s -1 @ T coldest Upper limit at OBF center: 1  10 -7  g cm -2 s -1 @ T OBF-ops Min to clean OBF in 1 orb: 2  10 -3  g cm -2 s -1 @ T OBF- bake O’Dell & Swartz (MSFC) Limits on Vaporization Rates

6. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 6 Monitoring the Contaminant:Transmission @ 700eV Grant (MIT)

7. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 7 Monitoring the Contaminant: C-K Optical Depth Marshall (MIT)

8. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 8 Summary of Bakeout Effort There will not be a Bakeout anytime soon We will continue to monitor the contaminant buildup and improve the characterization of the absorption of the contaminant MIT/ACIS will analyze CTI measurements at temperatures between -90 C and -120 C to understand the temperature dependence of the CTI better Calibration files for the time-dependent and spatial-dependent absorption of the contaminant are available in the CALDB & CIAO, we will continue to assess the accuracy of these corrections and update as necessary

9. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 9 Bonus Material: ACIS FP Temperature Anomaly ACIS DEA-A autonomously shutdown on 15 Sep 2005 Two unintended consequences of the recovery from this anomaly 1) FP temperature setpoint for -120 C was not loaded into the DEA-A 2)The A/D converter which reports the DEA Housekeeping data initialized into a low resolution mode The consequences of this were: 1) 16 Sep 2005 - 05 Oct 2005 - the FP temperature was not regulating and was 1.3 degrees colder than reported in TLM 2)06 Oct 2005 - 15 Oct 2005 - the FP temperature WAS regulating but the reported temperature was 1.3 degrees warmer than the actual temperature (-118.4 C instead of -119.7 C) The FP temperature regulation is back to nominal as of 15 Oct 2005

10. Chandra X-Ray Observatory CXC SOT, FOT, ACIS & MSFC PS October 19, 2005 10 FP Temperature Anomaly DePasquale (SAO)