Dec_06_1999 Shift m136 Start at 1999:340:20:00:00 GMT End 340:24:00:00 GMT See http://asc.harvard.edu/acis/SOT_reports/sot-shift.html, or /proj/ascwww/AXAF/extra/science/htdocs/acis/SOT_reports/Dec_06_1999_M136.txt. SOT Lead Ed Kellogg SOT FP FOT-SI HRC-SI ACIS-SI OTHER Plan: - Continue running load DEC0599 upcoming: 00579 LOCKMAN HOLE 1999:340:14:58:18.8 CAL-ER OBSID CAL-ER 1999:341:20:06:42.2 CAL-ER OBSID CAL-ER 1999:341:22:08:22.2 CAL-ER OBSID CAL-ER 1999:342:09:38:42.2 EVENTS DONE OBSID -------------- ---- ----- AOS 2300 579 See 3 fids, 4 stars as expexted , good images 2304 TLM dropouts, bit slips 2307 TLM appears stable 2312 ACIS Telecon ------------ Mark Bautz reviewed his email on damage status(appended to this report). Ameliorization could be done by the FEP, using the trap model discussed by Catherine. The idea is to keep track of preceding events. More data are needed to perfect the technique. XMM will launch into a similar orbit next Friday. A memo was sent to them about our techniques for protection.O"Dell: Damage to ACIS is correlated to an event near the belt entry, caused by a solar event. This kind of event is only predictable ~1hr in advance. No problem working at -120. Predict we could go to ~-138. Flexprints tested to -150. FEP0: have not seen the malfunction since day 307. High level testing of final patch is under way. We expect to load it in ~January. SI safing: level 2 approvals to be arranged; walkthrough on Thursday. A-side test to happen Monday, Dec 13. B-side to be later that week. Eric plans to distribute materials for review tomorrow. Bill Podgorski reports on SIM: way under tested values on number of SIM focus moves, a bit under on number of translation moves. NOTES/ISSUES/PROBLEMS --------------------- TLM not solid at beginning of pass - getting dropouts. Evaluation of QL data done at 1999:340:22:08 -------------------------------------------- The following observations from the last ten days should be available for review. If there is no comment after the entry, it means the image has not yet appeared in the book. OBSID Target Time Comment ----- ------ -------------- ------- 01463 Jupiter 1999:330:02:10 00961 Jupiter 1999:330:09:02 01475 HR1099 1999:331:05:34 01468 HR1099 1999:332:01:53 01467 CAS A, +Y MCP 1999:332:08:05 00100 X0614+091 1999:332:22:40 00077 CAL 83 1999:333:06:56 00325 S-Z CLUSTER 1999:337:07:22 00347 NGC 4151 1999:338:11:29 00125 SNR 509.0-68.7 1999:338:12:56 00324 NGC 4636 1999:339:00:13 00316 NGC 5128 1999:339:21:51 00910 RX J1159+5531 1999:340:09:04 As reported by Joy Nichols this morning, there were delays in processing recent data, so no new images are available today. From the chandra snapshot ------------------------- UTC 1999:340:23:04:01 (Mon Dec 6) f_ACE 1.74e+01 F_ACE 3.27e+06 R km 144635D OBT 1999:340:23:03:19 CTUVCDU 7049215 OBC s/w NRML FMT1_NORM CPEstat NORM OBT 60908599.84 ONLVCDU 7049208 OBC Errs 0 OBSID 579 EPState SUN SIM TTpos -50504 HETG Angle 80.6 PCADMODE NPNT RA 163.208 Bus V 30.24 SIM FApos -715 LETG Angle 79.1 PCONTROL NPNT Dec 57.463 Bus I 33.04 AOFSTAR GUID Roll 82.476 ACA Object FFFSSSSS Dither ENAB HRC-I HV ON ACA ImFunc TTTTTTTN Dith Yang 17.80 Yaw Rate 0.08 HRC-S HV OFF ACA CCD Temp -10.4 Dith Zang 6.90 Pitch Rate -0.07 OBSMode OBSV ACA Int Time 1.698 Roll Rate -0.19 Door OP ACT AOACSTAT OK FSS SunBeta SUN Door CL UNAC FSS Alfa -5.55 Batt 1 SOC 100.00% Avg HRMA Temp 70.61 FSS Beta -19.15 Batt 2 SOC 100.00% ACIS Stat7-0 64 Avg OBA Temp 50.89 SA Resolv 108.85 Batt 3 SOC 100.00% Cold Rad -120.7 OBA Tavg Fault NFLT SA Sun Pres ILLM Warm Rad -82.0 OBA Trng Fault NFLT +Y SA Amps 15.85 HRMA power 70.40 -Y SA Amps 16.84 EPHIN Geom LARG OBA power 89.40 +Y SA Temp 117.32 E1300 3 -Y SA Temp 116.22 P4GM 0 Roll Mom. -2.682 P41GM 0 Pitch Mom. -4.393 UpL Cmd Acc 65401 A-Leak 0.4320 Yaw Mom. 5.349 Cmd Rej A 120 B-Leak 0.0640 Mark Bautz's email on ACIS studies ---------------------------------- From: "Mark W. Bautz" Subject: ACIS CCD progress at MIT To: ctitask@head-cfa.harvard.edu, ht@head-cfa.harvard.edu (Harvey Tananbaum), cgrant@space.mit.edu (Catherine Grant), sek@space.mit.edu (Steve E. Kissel), gyp@space.mit.edu (Gregory Y. Prigozhin), fergason@space.mit.edu (Beverly LaMarr), garmire@astro.psu.edu (Gordon Garmire), fkb@space.mit.edu (Frederick K. Baganoff) Date: Sun, 5 Dec 1999 07:23:48 -0500 (EST) Cc: wfm@space.mit.edu (William F. Mayer), gregory@ll.mit.edu (Jim Gregory) Folks, In hopes of streamlingin Monday's telecon, here is a progress report on MIT efforts in support of the ACIS CCD investigation during the past two weeks. In summary: *We have established firm values for time constants of two defects, and idenfied one of them (the divacency) from energy-level measurements. *We have shown that both ground-irradiated and ACIS flight CCDS exhibit both of these defects; *We have begun very crude sacrificial charge modelling aimed at amelioration. Some improvement in energy resolution (30% decrease in FWHM) was obtained from an overly-simplified application of this model. There is some reason to believe this model is qualitatively correct. Details follow. mark OBJECTIVES: Of the four original investigation objectives, we are focussing now on the last two, viz., identifying the physical changes in the CCDs leading to CTI degradation, and developing methods to ameliorate the effects of the damage. DAMAGE CHARACTERIZATION: Flight data anlysis results: As reported at the previous telecon, we have now searched for traps with time constants in the range 0-200 msec (with the flight detector at a temperature of -110C) . We have identified two trap time constants: 110 microsec and about 4.9+-0.5 msec (the latter time is revised from our report last week of 2msec). The latter result is discussed in ACIS memo 177 by Catherine Grant (3 Dec. 1999). This week we obtained additional flight data at two other temperatures (-105C and -115C). We made these measurements to constrain trap energy levels (and thus permit trap identification) and to allow accurate charge loss modelling. Analysis is still in progress, but a preliminary result for the "short" trap (trap energy level of 0.21 ev (+- >0.02eV) below the conduction band, with a capture cross-section of 6e-16 cm**2, as determined by Gregory Prigozhin) allow us to identify the trap as the di-vacency (V-V) defect. In the -115C data Gregory reports indications of another trap with a very short timeconstant (a few tens of microsec). This very short trap may be the dominant source of CTI at temperatures below -115C. Pending analysis should soon yield trap energy level for the 5 msec trap. Laboratory results: Steve Kissel has used a charge injection technique to measure trap time constants in the CCDs irradiated recently at GSFC. We find evidence for two defects, with time constants of 8+-2 msec and "about" 100 microsec. More precise numbers will be available after additional analysis, but it seems likely that the lab. device shows at least the same two traps as the flight devices. Steve notes that at temperatures below about -100C, there is apparently no trap with timescales in the range 20 msec to 40 msec. This result is consistent with the finding that the flight device exhibits no evidence for traps with time-constants in the range 5 msec to 200 msec. AMELIORATION Modelling: We have begun to use the trap model discussed in Catherine's most recent memo to attempt to improve the energy resolution. A very simple model allows improvement of the energy resolution at 5.9 keV, in rows 800-100 of detector S2, from 750 eV to 500 eV (at focal plane temperature of -110C). This reconstruction included only sacrificial charge events of amplitude in excess of 5.9 keV. In fact, many other lower-amplitude events were ignored in this analysis and must be affecting the event amplitude. Understanding the importance of the amplitude of sacrificial charge events requires considerably more data than we have yet acquired; we have therefore requested that additional data be taken as part of the Dec. 12 load. We propose to trade "standard" CTI measurement time for raw-mode data acquisition time for this purpose. (We can still measure S2's CTI from the raw mode data; and we will still acquire CTI data from all detectors at least once per orbit.) At a more general level, an examination of the simplest sacrificial charge model indicates that, at least in the case of a single trap, RMS fluctuation in charge loss (and therefore, FWHM) is a nearly linear function of row number for row number >~200. Also, the ratio of mean to RMS charge loss is roughly independent of row number for rows >200. The flight data are consistent with this prediction of the sacrificial charge model, and reasonable parameter values (for background particle flux and for time constant) predict a value for this ratio which is similar to that observed in the flight data. (viz, RMS loss/mean loss in the range of 0.2 to 0.3, depending on conditions.) I believe this result justifies pursuit of this model in greater detail. PLANS Ground Irradiation experiments Rick Foster and Steve Brown devised a method to irradiate an entire quadrant of a CCID17. We hope to try this method a GSFC in early January (tentatively Jan 6). We hope to perform the cold irradiation experiment, using a CCID7 and the PSU camera, at the same time. The wafer DLTS studies may not be completed until later in January. Flight Data Acquistion. As noted above, we will acquire additional raw-mode data (at -110C) during the Dec. 12 load. The team believes that data (probably in raw mode) at lower temperatures (below -120C) should be acquired soon. Lowering the focal plane temperature to -120C has been the most effective of all amelioration measures taken to date, so it is extremely important to understand whether even lower temperatures should be contemplated. Lab. measurements are underway to characterize the GSFC-irradiated devices in this temperature range. Since the flight focal plane has not been cooled below -120C since launch (it saw -128C in ground testing), and since long cool-down times are involved, we asked the ACIS engineering staff to recommend procedures for low-temperature measurements.