Description

Assumptions

It is assumed that the input science data have had the zero group (or bias) subtracted. Accordingly, the dark reference data should have their own group zero subtracted from all groups.

Algorithm

The dark current step removes dark current from a Roman exposure by subtracting dark current rate data stored in a dark reference file from the fitted ramp data.

The current implementation uses dark reference files for a given detector that have the rate of the accumulated dark current measured and stored in the dark_slope array in the reference file. The dark rate are then subtracted from the fitted ramp data.

The DQ flags from the dark reference file are propagated into science exposure DQ array using a bitwise OR operation.

Upon successful completion of the dark subtraction the cal_step attribute is set to “COMPLETE”.

Special Handling

Any pixel values in the dark reference data that are set to NaN will have their values reset to zero before being subtracted from the science data, which will effectively skip the dark subtraction operation for those pixels.