-John MacKenty and Sylvia Baggett
29 May 1992.
Measles Contamination:
The WF/PC-1 camera heads were decontaminated on Day 1992.034 (Feb. 03), following a long period of continuous cold operation of the WF/PC-1 CCD detectors during which many GO/GTO science observations were obtained. The decontamination procedure restored UV transmission (temporarily), blue performance, and reduced the internal scattered light. It also made the expected small changes in the flat field structure but did not re-introduced QEH.
However, unlike previous decontaminations, the procedure has resulted in the re-appearance of the "measles" contaminant. These features are mainly ~1% structures covering most of the field of view and are thought to be located on the outside surface of the field flattening windows immediately in front of the detectors. Detectors W2 and P6 are the least affected CCD's and P7 and P8 are probably the most affected.
The decontamination procedure we followed was identical to used to recover from the partial WF/PC-1 safing on 03 July 1991 (which successfully removed the measles created by that safing event). Because of the measles, we repeated the decontamination on Day 192.035 (Feb. 04) but this only slightly decreased the degree of measles contamination. JPL analysis and prior experience with the measles contaminant led to a further execution of a different decontamination procedure on 1992.063 (March 03) and a repeat of the original procedure on 1992.068 (March 08). These two procedures did not remove the measles contaminant.
The next efforts to remove the contaminants will take at least 2 to 3 months to prepare. This memo is directed to observers analyzing data obtained after 03 February 1992 to both inform them of what data exists to compensate for the measles features in their data and also to request that they provide feedback to the STScI as to the extent that the measles affect their data. Since there is both cost in spacecraft time and some risks to the WF/PC-1 in the next set of procedures being considered, it is necessary to determine if there is a significantly compelling scientific need to remove the measles.
Internal Flat Field Exposures (Delta Flats):
Since each decontamination procedure changes the structure of the flat fields and assembling a new flat field calibration from observations of the sunlit earth requires many observations, internal calibration lamp exposures for a limited set of filters have been obtained twice per month since late December 1991. Some other internal lamp exposures have also been obtained as part of the calibration program. This lamp is not bright and therefore only broadband, longer wavelength internal flat fields can be obtained. While these internal flat field exposures are not directly useful for flat field calibration, the ratio of an internal flat obtained prior to the decontamination to an internal flat obtained closest in time and wavelength to a particular science observation can be used to partially "correct" the existing flat field calibration file.
To facilitate the calibration of recent WF/PC-1 observations, this memo presents an inventory of recent internal flats suitable for use in the generation of delta flats. There are currently three proposals for which internal flats (intflats) are obtained on a regular basis. The 2876 proposal for Cycle 1 calibration internal flats is executed approximately every two weeks. The details on these intflats have been summarized in Table 1. Useful intflats are obtained for:
WFC: F439W, F547W, F555W, F622W, F702W
PC: F439W, F547M, F555W, F785LP
The other two proposals obtain more frequent intflats but only for F439W and F555W in both cameras and occasionally F785LP in PC. These intflats are listed in Table 2 (WFC) and Table 3 (PC). All tables specify the filter, camera, exposure time, and date of each observation. Due to the different reflectivity characteristics of the two shutter blades, the shutter in use is listed as well. In addition to the variations in the overall streak patterns, blade A exhibits obvious internal reflections in group 4 while blade B has these reflections in group 2. The exposure times given in the tables should be used rather than those in the image headers since the EXPTIME keyword for intflat longer than 80 sec (but only for INTFLATS), taken after Feb. 10, 1992, is incorrect.
Tables updated 29 May 1992.
============================================================================
Table 1 -- Cycle 1 Calibration Internal Flats
----------------------------------------------------------------------------
filt cam exptime 24-Dec-91 10-Jan-92 23-Jan-92 07-Feb-92 21-Feb-92
F439W WF 100.00 w0t70201t w0t70501t w0t70601t w0t70701t w0t70801t
F547M WF 26.00 w0t70202t w0t70502t w0t70602t w0t70702t w0t70802t
F555W WF 7.00 w0t70203t w0t70503t w0t70603t w0t70703t w0t70803t
F622W WF 2.60 w0t70204t w0t70504t w0t70604t w0t70704t w0t70804t
F702W WF 0.70 w0t70206t w0t70506t w0t70606t w0t70706t w0t70806t
shutter A B B A B
23-Dec-91 10-Jan-92 25-Jan-92 07-Feb-92 20-Feb-92
F439W PC 350.00 w0t70l01t w0t70o01t w0t70p01t w0t70q01t w0t70r01t
F547M PC 80.00 w0t70l02t w0t70o02t w0t70p02t w0t70q02t w0t70r02t
F555W PC 23.00 w0t70l03t w0t70o03t w0t70p03t w0t70q03t w0t70r03t
F785LP PC 0.50 w0t70l06t w0t70o06t w0t70p06t w0t70q06t w0t70r06t
shutter A B B B B
----------------------------------------------------------------------------
filt cam exptime 02-Mar-92 17-Mar-92 01-Apr-92 15-Apr-92 20-Apr-92
F439W WF 100.00 w0t70901t w0t70a01t w0t70b01t w0t70c01t w0t70d01t
F547M WF 26.00 w0t70902t w0t70a02t w0t70b02t w0t70c02t w0t70d02t
F555W WF 7.00 w0t70903t w0t70a03t w0t70b03t w0t70c03t w0t70d03t
F622W WF 2.60 w0t70904t w0t70a04t w0t70b04t w0t70c04t w0t70d04t
F785LP WF 0.30 --- --- --- w0t70c05t w0t70d05t
F702W WF 0.70 w0t70906t w0t70a06t w0t70b06t w0t70c06t w0t70d06t
shutter B B A A A
02-Mar-92 17-Mar-92 02-Apr-92 18-Apr-92 25-Apr-92
F439W PC 350.00 w0t70s01t w0t70t01t w0t70u01t w0t70v01t w0t70w01t
F547M PC 80.00 w0t70s02t w0t70t02t w0t70u02t w0t70v02t w0t70w02t
F555W PC 23.00 w0t70s03t w0t70t03t w0t70u03t w0t70v03t w0t70w03t
F622W PC 7.00 --- --- --- w0t70v04t w0t70w04t
F702W PC 1.60 --- --- --- w0t70v05t w0t70w05t
F785LP PC 0.50 w0t70s06t w0t70t06t w0t70u06t w0t70v06t w0t70w06t
F718M PC 8.00 --- --- --- w0t70v07t w0t70w07t
shutter B B B A A
----------------------------------------------------------------------------
filt cam exptime 28-Apr-92 04-May-92 13-May-92 21-May-92
F439W WF 100.00 w0t70e01t w0t70f01t w0t70g01t w0t70h01t
F547M WF 26.00 w0t70e02t w0t70f02t w0t70g02t w0t70h02t
F555W WF 7.00 w0t70e03t w0t70f03t w0t70g03t w0t70h03t
F622W WF 2.60 w0t70e04t w0t70f04t w0t70g04t w0t70h04t
F785LP WF 0.30 w0t70e05t w0t70f05t w0t70g05t w0t70h05t
F702W WF 0.70 w0t70e06t w0t70f06t w0t70g06t w0t70h06t
shutter A A B B
30-Apr-92 05-May-92 12-May-92 21-May-92
F439W PC 350.00 w0t70x01t w0t70y01t w0t70z01t w0t71001t
F547M PC 80.00 w0t70x02t w0t70y02t w0t70z02t w0t71002t
F555W PC 23.00 w0t70x03t w0t70y03t w0t70z03t w0t71003t
F622W PC 7.00 w0t70x04t w0t70y04t w0t70z04t w0t71004t
F702W PC 1.60 w0t70x05t w0t70y05t w0t70z05t w0t71005t
F785LP PC 0.50 w0t70x06t w0t70y06t w0t70z06t w0t71006t
F718M PC 8.00 w0t70x07t w0t70y07t w0t70z07t w0t71007t
shutter B B B B
=========================================================
Table 2 Internal WF Flats from Monitoring Programs
---------------------------------------------------------
expdate expstart filter cam exptime rootname shutter
02-Jan-92 04:24:18 F555W WF 7.00 W0LC2B01T B
05-Jan-92 09:48:18 F555W WF 7.00 W0QI0Y01T B
07-Jan-92 07:27:18 F555W WF 7.00 W0QI0Z01T B
12-Jan-92 04:56:18 F555W WF 7.00 W0QI1001T B
15-Jan-92 19:23:18 F555W WF 7.00 W0QI1101T B
18-Jan-92 19:23:18 F555W WF 7.00 W0QI1201T A
22-Jan-92 09:05:18 F555W WF 7.00 W0QI1301T B
26-Jan-92 12:38:18 F555W WF 7.00 W0QI1401T A
29-Jan-92 15:48:18 F555W WF 7.00 W0QI1501T A
02-Feb-92 04:16:18 F555W WF 7.00 W0QI1601T B
03-Feb-92 22:30:17 F555W WF 7.00 W0QI6701T A
03-Feb-92 23:31:17 F555W WF 7.00 W0QI6801T A
04-Feb-92 22:14:17 F555W WF 7.00 W0QI7701T B
04-Feb-92 22:28:17 F555W WF 7.00 W0QI7801T B
14-Feb-92 20:52:17 F555W WF 7.00 W0QI1901T B
17-Feb-92 17:19:17 F555W WF 7.00 W0QI1B01T B
21-Feb-92 06:09:17 F555W WF 7.00 W0QI1C01T B
24-Feb-92 15:22:17 F555W WF 7.00 W0QI1D01T B
28-Feb-92 21:05:17 F555W WF 7.00 W0QI1E01T A
03-Mar-92 00:22:17 F555W WF 7.00 W0LC2L01T B
03-Mar-92 21:31:17 F555W WF 7.00 W0QI1F01T B
07-Mar-92 16:43:17 F555W WF 7.00 W0QI1G01T A
11-Mar-92 08:54:17 F555W WF 7.00 W0QI1H01T B
15-Mar-92 03:58:17 F555W WF 7.00 W0QI1I01T A
19-Mar-92 04:45:17 F555W WF 7.00 W0QI1J01T B
22-Mar-92 15:26:17 F555W WF 7.00 W0QI1K01T B
25-Mar-92 17:05:17 F555W WF 7.00 W0QI1L01T A
28-Mar-92 18:32:17 F555W WF 7.00 W0QI1M01T B
31-Mar-92 12:46:17 F555W WF 7.00 W0LC2V01T B
02-Apr-92 09:40:17 F555W WF 7.00 W0QI1N01T B
05-Apr-92 16:24:17 F555W WF 7.00 W0QI1O01T B
08-Apr-92 18:37:17 F555W WF 7.00 W0QI1P01T A
12-Apr-92 05:58:17 F555W WF 7.00 W0QI1Q01T B
16-Apr-92 12:01:17 F555W WF 7.00 W0QI1R01T A
19-Apr-92 12:32:17 F555W WF 7.00 W0QI1S01T A
22-Apr-92 14:11:17 F555W WF 7.00 W0QI1T01T A
25-Apr-92 16:04:17 F555W WF 7.00 W0QI1U01T A
28-Apr-92 17:11:17 F555W WF 7.00 W0LC3501T
28-Apr-92 23:39:17 F555W WF 7.00 W0QI1V01T B
02-May-92 02:40:17 F555W WF 7.00 W0QI1W01T B
05-May-92 09:20:17 F555W WF 7.00 W0QI1X01T A
09-May-92 01:51:17 F555W WF 7.00 W0QI1Y01T A
13-May-92 20:53:17 F555W WF 7.00 W0QI1Z01T A
17-May-92 00:53:17 F555W WF 7.00 W0QI1701T B
20-May-92 12:50:17 F555W WF 7.00 W0QI1801T B
23-May-92 16:54:17 F555W WF 7.00 W0QI1A01T B
26-May-92 00:29:17 F555W WF 7.00 W0LC3F01T B
-----------------------------------------------------
30-Dec-91 02:18:18 F439W WF 100.00 W0LC2A01T A
30-Dec-91 02:22:18 F439W WF 100.00 W0LC2A02T A
30-Dec-91 02:59:18 F439W WF 100.00 W0LC2A04T A
06-Mar-92 05:45:17 F439W WF 100.00 W0LC2K01T A
06-Mar-92 05:49:17 F439W WF 100.00 W0LC2K02T A
06-Mar-92 06:26:17 F439W WF 100.00 W0LC2K04T A
31-Mar-92 13:59:17 F439W WF 100.00 W0LC2U01T B
31-Mar-92 14:03:17 F439W WF 100.00 W0LC2U02T B
31-Mar-92 14:40:17 F439W WF 100.00 W0LC2U04T B
28-Apr-92 04:00:17 F439W WF 100.00 W0LC3401T B
28-Apr-92 04:04:17 F439W WF 100.00 W0LC3402T B
28-Apr-92 04:41:17 F439W WF 100.00 W0LC3404T B
=========================================================
Table 3 Internal PC Flats from Monitoring Programs
---------------------------------------------------------
expdate expstart filter cam exptime rootname shutter
30-Dec-91 00:31:18 F439W PC 360.00 W0LC2E01T A
30-Dec-91 00:41:18 F439W PC 360.00 W0LC2E02T A
30-Dec-91 01:24:18 F439W PC 360.00 W0LC2E04T A
01-Jan-92 02:35:18 F439W PC 360.00 W0QI2G01T B
01-Jan-92 02:45:18 F439W PC 360.00 W0QI2G02T B
09-Jan-92 13:45:18 F439W PC 360.00 W0QI2H01T B
09-Jan-92 13:55:18 F439W PC 360.00 W0QI2H02T B
18-Jan-92 19:35:18 F439W PC 360.00 W0QI2I01T A
18-Jan-92 19:45:18 F439W PC 360.00 W0QI2I02T A
23-Jan-92 05:58:18 F439W PC 360.00 W0QI2J01T B
23-Jan-92 06:08:18 F439W PC 360.00 W0QI2J02T B
02-Feb-92 05:54:18 F439W PC 360.00 W0QI2K01T B
02-Feb-92 06:04:18 F439W PC 360.00 W0QI2K02T B
03-Feb-92 22:05:17 F439W PC 360.00 W0QI7L01T A
03-Feb-92 22:15:17 F439W PC 360.00 W0QI7L02T A
04-Feb-92 23:52:17 F439W PC 360.00 W0QI8L01T B
05-Feb-92 00:02:17 F439W PC 360.00 W0QI8L02T B
15-Feb-92 18:44:17 F439W PC 360.00 W0QI2M01T B
15-Feb-92 18:54:17 F439W PC 360.00 W0QI2M02T B
18-Feb-92 10:38:17 F439W PC 360.00 W0QI2N01T B
18-Feb-92 10:48:17 F439W PC 360.00 W0QI2N02T B
28-Feb-92 21:52:17 F439W PC 360.00 W0QI2O01T A
28-Feb-92 22:02:17 F439W PC 360.00 W0QI2O02T A
05-Mar-92 00:52:17 F439W PC 360.00 W0QI2P01T B
05-Mar-92 01:02:17 F439W PC 360.00 W0QI2P02T B
09-Mar-92 10:49:17 F439W PC 360.00 W0LC2O01T B
09-Mar-92 10:59:17 F439W PC 360.00 W0LC2O02T B
09-Mar-92 11:42:17 F439W PC 360.00 W0LC2O04T B
12-Mar-92 18:33:17 F439W PC 360.00 W0QI2Q01T B
12-Mar-92 18:43:17 F439W PC 360.00 W0QI2Q02T B
18-Mar-92 04:07:17 F439W PC 360.00 W0QI2R01T B
18-Mar-92 04:17:17 F439W PC 360.00 W0QI2R02T B
25-Mar-92 04:08:17 F439W PC 360.00 W0QI2S01T B
25-Mar-92 04:18:17 F439W PC 360.00 W0QI2S02T B
31-Mar-92 19:13:17 F439W PC 360.00 W0QI2T01T B
31-Mar-92 19:23:17 F439W PC 360.00 W0QI2T02T B
01-Apr-92 00:14:17 F439W PC 360.00 W0LC2Y01T B
01-Apr-92 00:24:17 F439W PC 360.00 W0LC2Y02T B
01-Apr-92 01:07:17 F439W PC 360.00 W0LC2Y04T B
07-Apr-92 00:28:17 F439W PC 360.00 W0QI2U01T B
07-Apr-92 00:38:17 F439W PC 360.00 W0QI2U02T B
19-Apr-92 19:18:17 F439W PC 360.00 W0QI2V01T A
19-Apr-92 19:28:17 F439W PC 360.00 W0QI2V02T A
27-Apr-92 03:42:17 F439W PC 360.00 W0QI2W01T A
27-Apr-92 03:52:17 F439W PC 360.00 W0QI2W02T A
30-Apr-92 23:12:17 F439W PC 360.00 W0QI2X01T B
30-Apr-92 23:22:17 F439W PC 360.00 W0QI2X02T B
05-May-92 09:32:17 F439W PC 360.00 W0QI2Y01T A
05-May-92 09:42:17 F439W PC 360.00 W0QI2Y02T A
12-May-92 02:18:17 F439W PC 360.00 W0QI2Z01T B
12-May-92 02:28:17 F439W PC 360.00 W0QI2Z02T B
22-May-92 15:48:17 F439W PC 360.00 W0QI3001T B
22-May-92 15:58:17 F439W PC 360.00 W0QI3002T B
26-May-92 01:04:17 F439W PC 360.00 W0QI3101T B
26-May-92 01:14:17 F439W PC 360.00 W0QI3102T B
-----------------------------------------------------
22-Dec-91 09:53:18 F555W PC 35.00 W0QI0U02T A
23-Dec-91 15:49:18 F555W PC 35.00 W0QI0V02T A
27-Dec-91 05:57:18 F555W PC 35.00 W0QI0W02T A
31-Dec-91 16:50:18 F555W PC 35.00 W0QI0X02T B
03-Jan-92 01:23:18 F555W PC 23.00 W0LC2F01T A
05-Jan-92 09:55:18 F555W PC 35.00 W0QI0Y02T B
07-Jan-92 07:34:18 F555W PC 35.00 W0QI0Z02T B
12-Jan-92 05:03:18 F555W PC 35.00 W0QI1002T B
15-Jan-92 19:30:18 F555W PC 35.00 W0QI1102T B
18-Jan-92 19:30:18 F555W PC 35.00 W0QI1202T A
22-Jan-92 09:12:18 F555W PC 35.00 W0QI1302T B
26-Jan-92 12:45:18 F555W PC 35.00 W0QI1402T A
29-Jan-92 15:55:18 F555W PC 35.00 W0QI1502T A
02-Feb-92 04:23:18 F555W PC 35.00 W0QI1602T B
03-Feb-92 22:37:17 F555W PC 35.00 W0QI6702T A
03-Feb-92 23:38:17 F555W PC 35.00 W0QI6802T A
04-Feb-92 22:21:17 F555W PC 35.00 W0QI7702T B
04-Feb-92 22:35:17 F555W PC 35.00 W0QI7802T B
14-Feb-92 20:59:17 F555W PC 35.00 W0QI1902T B
17-Feb-92 17:26:17 F555W PC 35.00 W0QI1B02T B
21-Feb-92 06:16:17 F555W PC 35.00 W0QI1C02T B
24-Feb-92 15:29:17 F555W PC 35.00 W0QI1D02T B
28-Feb-92 21:12:17 F555W PC 35.00 W0QI1E02T A
03-Mar-92 07:38:17 F555W PC 23.00 W0LC2P01T B
03-Mar-92 22:15:17 F555W PC 35.00 W0QI1F02T B
07-Mar-92 16:50:17 F555W PC 35.00 W0QI1G02T A
11-Mar-92 09:01:17 F555W PC 35.00 W0QI1H02T B
15-Mar-92 04:05:17 F555W PC 35.00 W0QI1I02T A
19-Mar-92 04:52:17 F555W PC 35.00 W0QI1J02T B
22-Mar-92 15:33:17 F555W PC 35.00 W0QI1K02T B
25-Mar-92 17:12:17 F555W PC 35.00 W0QI1L02T A
28-Mar-92 18:39:17 F555W PC 35.00 W0QI1M02T B
31-Mar-92 19:05:17 F555W PC 23.00 W0LC2Z01T B
02-Apr-92 09:47:17 F555W PC 35.00 W0QI1N02T B
05-Apr-92 16:31:17 F555W PC 35.00 W0QI1O02T B
08-Apr-92 18:44:17 F555W PC 35.00 W0QI1P02T A
12-Apr-92 06:05:17 F555W PC 35.00 W0QI1Q02T B
16-Apr-92 12:08:17 F555W PC 35.00 W0QI1R02T A
19-Apr-92 12:39:17 F555W PC 35.00 W0QI1S02T A
22-Apr-92 14:18:17 F555W PC 35.00 W0QI1T02T A
25-Apr-92 16:11:17 F555W PC 35.00 W0QI1U02T A
28-Apr-92 23:46:17 F555W PC 35.00 W0QI1V02T B
30-Apr-92 15:20:17 F555W PC 23.00 W0LC3901T A
02-May-92 02:47:17 F555W PC 35.00 W0QI1W02T B
05-May-92 09:27:17 F555W PC 35.00 W0QI1X02T A
09-May-92 01:58:17 F555W PC 35.00 W0QI1Y02T A
13-May-92 21:00:17 F555W PC 35.00 W0QI1Z02T A
17-May-92 01:00:17 F555W PC 35.00 W0QI1702T B
20-May-92 12:57:17 F555W PC 35.00 W0QI1802T B
23-May-92 17:01:17 F555W PC 35.00 W0QI1A02T B
-----------------------------------------------------
03-Jan-92 01:26:18 F785LP PC 0.50 W0LC2F02T A
03-Mar-92 07:41:17 F785LP PC 0.50 W0LC2P02T B
31-Mar-92 19:08:17 F785LP PC 0.50 W0LC2Z02T B
30-Apr-92 15:23:17 F785LP PC 0.50 W0LC3902T A