Non-Linearity Correction Algorithm for the WFC3 IR Channel

WFC3 IR channel data are obtained in the form of multiple, non-destructive readouts, grouped into “ramps”, similar to the method employed by NICMOS. This strategy facilitates the characterization of the non-linearity of the IR Focal Plane Array (FPA), as the detector’s response to a steady signal can be measured multiple times, until the detector becomes saturated. Using test data collected in this manner, the determination of correction coefficients for non-linearity in the WFC3 IR channel is performed through polynomial fits to the measured and ideal signal levels.