A lookup table for each band was used to determine the cross-scan distance over which a source might cause optical crosstalk detections. This was a function of the signal-to-noise ratio of the source, and was based on the prelaunch evaluation of the optical point-spread function. The signal-to-noise ratio thresholds for closer examination were 5000, 1200, 300, and 200 in the 12, 25, 60, and 100 µm bands, respectively. When a detection was above this threshold the cross-scan distance to search for other detections caused by crosstalk was obtained from the lookup table. The in-scan search distance was constant, with values of 14", 14", 29", and 58" in the 12, 25, 60, and 100 µm bands, respectively. Any detections in the window which were fainter than the one being processed were deleted from further consideration. The deletions were performed only for the module containing the detector which yielded the bright source, in order not to eliminate its confirmation partner.
No attempt was made to identify crosstalk caused by the secondary mirror support spider. The characteristics of the bright source and those deleted were subsequently used in the small extended source processing. An analysis of the effects of bright sources is given in Section VII.E.5.