The Sandia National Laboratory 2-channel radiometer uses two narrow-band (10 nm) filters in the red and near-IR at a sampling rate of many thousands per second. It measures the total radiative output of the SRC during entry in the 380-600 nm band and the 600-900 nm band and detect rapid fluctuations of light output from spacecraft rotation, instabilities in the shock layer, and ablation.

This instrument consists of two photometers, each equipped with a filter of choice: here a low-pass and high-pass cut-off filter. Each photometer measures the sky over a large ~15 degree field of view, at about 5 - 35 degree elevation.