Spectral and radiometric performance of the Goddard laser for absolute measurement of radiance

The Goddard Laser for Absolute Measurement of Radiance (GLAMR) is a mobile spectral and radiometric sensor characterization facility based at NASA/Goddard Space Flight Center. Based on NIST’s traveling Spectral Irradiance and Radiance Calibration using Uniform Sources (SIRCUS), GLAMR consists of a system of tunable lasers to generate quasi-monochromatic energy between 310 and 2500nm, a large integrating sphere to provide a full aperture uniform source, a control system to automate operations and a data system to record and serve telemetry. GLAMR was used to characterize the Ocean Color Instrument (OCI) to be launched aboard the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission. The test of the OCI flight instrument took place in October 2022. GLAMR will be used to characterize the CLARREO Pathfinder (CPF) instrument in September 2023. Both programs had stringent calibration requirements on GLAMR, necessitating additional characterization of GLAMR radiometric uncertainty and improvements in the NIST traceability. This paper will discuss the improvement in the GLAMR uncertainty budget and the performance of GLAMR for the OCI instrument as well as the upcoming test for CPF.