The MITLL3 DEFECTS

The information provided here is based on John Barton's MITLL3 Test Summary report of 21 October 1998. A complete copy of that report is available here.

• Hot pixels cause saturated columns and weaker vertical trails in bias frames. In long dark frames weaker hot pixels may also saturate pixels locally about the hot pixel site, faint hot pixels become more prominant and some that are  undetectable at short integration become prominent. A defect map may be needed to assist observers in the placement of their obejects.
• The trailed charge from hot pixels can appear to start up unexpectedly in windowed images when the hot pixel is not contained within the window. The trailed charge is, however, in the expected column containing the hot pixel and is of the expected intensity.

TRAPPING SITES

A quick look for trapping sites has revealed only a small number of obvious traps. The co-ordinates given are with respect to the first pixel out (of output amplifier A) being pixel (1, 1). Those with unknown Y co-ordinates have been detected only by their trailed charge into the Y overscan region.

• ( 472, 488) consuming about 160 e-
• ( 726, 1064) 250
• ( 766, 240) 2000
• (1032, ????)
• (1272, ????)
• (1441, ????)
• (1952, ????)
• (1956, ????)

There are probably many smaller traps that have remained undetected. These may become prominent in charge shuffling readouts.

HOT PIXEL DEFECTS

In the following defect lists the co-ordinates are with respect to the first pixel out of AMP-A being pixel (1, 1). Charge intensities apply to NORMAL readout mode and a CCD operating temperature of 160K. Intensities will be different at other readout rates and temperatures.

BRIGHT DEFECTS LIST

See the appendix to the MITLL3 Test Summary report for a more complete description of defects found earlier in the CCD setup, some of which have since changed but may return.

Several CCD columns show trailed charge on bias and dark frames due to the presence of hot pixels. The trails are brightened columns that follow the defect site in the readout. They follow after the defect site because the slower readout allows sufficient time for the defect to deposit charge in the column pixels as these pixels are shifted through the defect site. For all but the major defect there is insufficient time to accumulate a measurable charge in pixels ahead of the defect site as each column pixel is swept rapidly through the defect site during the fast cleanout process. Only the major defect is sufficiently intense to deposit a measurable charge ahead of the defect site.

The following CCD columns trail charge on bias and dark frames due to hot pixels at the locations indicated. The intensity measurements (e-/pix) apply only for a NORMAL speed readout and the CCD operated at 160K.

Column

• 168 due to hot pixel at ( 168, 3473) .... NOT SEEN LATELY
• 239 due to hot pixel at ( 239, 4096/7) trails 12 e-/pix
• 349 due to hot pixel at ( 349, 3920/1) trails 4 e-/pix
• 733/4 rejected columns due to a major defect at (733/4, 3821) trails
• 240 and 280 e-/pix in columns 733/4
• 1050/1 due to hot pixel at (1050/1,1219) trails 1 and 3 e-/pix
• 1091 due to hot pixel at (1091,1255/6) trails 3 e-/pix
• 1138-51 including rejected columns affected by the MAJOR DEFECT centred at (1144,1228) - see below for intensities
• 1157/8 due to hot pixel at (1157/8,1233) trails 12 and 3 e-/pix
• 1213/4 due to hot pixel at (1213/4, 437) trails 3 and 2 e-/pix
• 1298 due to hot pixel at (1298,1505/6) trails 4 e-/pix
• 1316/7/8 including rejected column due to hot pixel at (1317, 155) trails 1, 80 and 3 e-/pix
• 1497 rejected column affected by the major defect at (1497, 3477) trails 550 e-/pix
• 1922/3 due to hot pixel at (1922/3, 1893) trails 6 e-/pix just beyond the defect but trails fade to zero over last columns  read out
• 2048 rejected column due to some sort of intermittent edge effect

HOT PIXEL DEFECTS FOUND IN 2000 SECOND DARK FRAMES

Peak search routines were used to detect and list hot pixels and cosmic ray events in 2000 sec dark frames at a CCD temperature of 160K. The routine rejected known defective columns from inclusion in these lists. Columns 733, 734, 1143, 1144, 1145, 1146, 1317, 1497 and 2048 were completely rejected from the listing owing to severe defects at (733/4, 3821), (1144,1228), (1317, 155), (1497, 3477) and an erratic last column 2048. Processing several such repeated dark frames, enabled a table of repeating defects to be compiled.

In the following table defect co-ordinates are based on (1, 1) being the first pixel read out of the CCD's AMP-A. The Intensity  is the defect's intensity, measured in ADUs (gain 1.75 e-/pix) above the bias level. The Count  is the number of dark frames displaying the defect. Thus, cnt = 4 indicates that the defect was found on all four dark frames whereas a cnt = 2 indicates it appeared on only two frames and may therefor be a remnant of a cosmic ray event or perhaps a pixel a little distant from an erratic hot pixel.

(X,Y)	Intensity	Count	(X,Y)	Intensity	Count
( 209, 127)	112	4	(1316, 154)	65132	2
(1295, 178)	11625	4	( 599, 278)	316	4
( 517, 315)	198	4	( 604, 369)	422	4
(1082, 401)	31	3	(1213, 437)	23267	4
(1956, 517)	6884	4	(1952, 519)	986	4
(1335, 553)	534	4	(1553, 582)	191	3
( 823, 638)	946	2	( 607, 699)	669	2
( 811, 778)	533	4	(1580, 807)	143	4
( 191, 821)	29	4	( 835, 938)	199	4
(1165,1054)	215	4	( 982,1130)	1152	4
(1105,1145)	97	4	(1933,1171)	5555	4
(1131,1176)	38	4	( 754,1193)	2287	4
(1027,1204)	135	4	(1100,1205)	3328	4
( 957,1210)	91	2	( 956,1210)	100	2
( 786,1211)	24	3	(1051,1218)	31956	4
( 969,1220)	391	4	( 952,1225)	1605	4
(1147,1232)	67	2	(1157,1232)	65138	4
(1086,1234)	544	4	(1154,1237)	153	4
(1112,1244)	151	4	(1043,1249)	49	3
(1136,1251)	21	4	( 47,1252)	25	2
(1122,1253)	55	4	(1013,1255)	95	4
(1091,1255)	24382	4	(1050,1299)	256	4
( 253,1349)	235	4	( 857,1353)	148	2
( 871,1353)	104	4	( 857,1354)	96	2
( 802,1370)	222	4	( 807,1387)	610	4
( 242,1405)	36	4	(1860,1474)	5392	2
(1562,1490)	203	4	(1298,1503)	65138	2
(1298,1504)	65138	2	(1298,1507)	65132	2
(1390,1521)	26	3	(1913,1599)	307	4
(1923,1893)	5317	4	( 710,2238)	1157	4
( 391,2289)	998	4	(1699,2351)	450	3
( 688,2572)	530	4	( 683,2630)	1559	2
(1591,2813)	26	4	(1272,2957)	5121	4
( 268,3051)	130	4	(1599,3143)	598	4
(1309,3239)	40	4	( 965,3293)	2475	4
(1842,3345)	102	4	(2008,3432)	6581	4
( 168,3472)	2595	4	( 749,3614)	99	4
(1441,3624)	2962	4	(1441,3628)	96	4
(1441,3632)	40	4	(1032,3678)	245	4
( 732,3820)	65132	4	( 736,3821)	3063	4
( 349,3920)	11740	4	(1123,3951)	680	3
( 239,4096)	65138	4