Mike Skrutskie had asked us to check for degradation in the H-band array by looking at the nightly generated H-band masks for periods bracketting the partial thermal cycles on October 14, 1998, and November 2, 1998, at the northern facility.
The total number of pixels masked off at all three bands is shown in the table below for two periods roughly centered on the two partial thermal cycles. (Gaps in the day sequence indicate nights when darks/flats were not taken and thus nightly masks could not be generated.) Across these thermal cycles, the number of masked pixels at J and Ks bands are essentially unchanged. (The number at Ks actually appears to decrease after the second cycle.) However, the H array does have 10-20 new masked pixels on average after each thermal cycle.
Observation R1 R1 R1 R2-1 R2-1 R2-1 Date J H Ks J H Ks ----------- ---- ---- ---- ---- ---- ---- 981012n 940 1082 1401 765 1085 803 981013n 941 1086 1401 766 1089 802 981014n 940 1080 1401 764 1082 796 <-- thermal cycle 981015n 940 1099 1400 766 1101 808 981016n 940 1095 1399 765 1098 802 981019n 940 1092 1399 765 1095 808 --------------------------------------------------------------- 981031n 940 1078 1399 765 1080 802 981101n 940 1095 1399 765 1097 802 981102n 940 1096 1399 764 1099 798 <-- thermal cycle 981103n 940 1105 1400 764 1107 791 981107n 940 1129 1400 766 1132 798 981111n 941 1118 1401 766 1121 793 ---------------------------------------------------------------
The H-band nightly generated masks are shown below for three representative dates bracketting the above partial thermal cycles. The three columns show masks for 981012n, 981016n, and 981111n, respectively. The first row shows the Read1 masks whereas the second shows the Read2-Read1 masks.