CCD Safety Check is performed in PhaseI. The danger frame indicator is cleared by the PhaseI Initialization Routine . The main program calls the Flags Routine which checks the FDB and sets the safety check parameter as required. The Phase I main code executes Bad Pixel Correction and calls the safety check routine if the flag is set. The safety routine extracts the camera mode from the FDB. If the mode is more than 3, indicating a partial read, the routine exits. The image data is binned or extracted to 128x128, i.e., 1x1 frames are binned 8x8, 2X2 frames are binned 4x4, etc. The routine then executes the histogram instruction. Based on the initial camera mode selects a histogram bin and threshold for comparison. If the threshold is exceeded, the danger count is incremented and the safe frame count is set to 0. If the danger count is greater than or equal to the danger count threshold, word 11 of the results block is set to non-zero. If the histogram threshold is not exceeded, the safe frame count is incremented. If the safe frame count is greater than or equal to the safe frame count threshold, the danger frame count is set to zero.

The following table defines the parameters used by safety checks that must be set by sequence or telecommand. Register number are decimal. These registers appear in the image header beginning at location 426. Registers 684 through 693 must be set for the safety frame check to be meaningful.