GSFC Calibration Laboratory improvement of broadband source calibration through continuous monitoring

Within the NASA GSFC Code 618 Calibration Laboratory, the Radiometric Calibration Lab (RCL) is focused on maintaining National Institute of Standards and Technology (NIST) traceable calibrated sources and detectors to calibrate, characterize, and monitor remote sensing instrumentation throughout NASA and the larger scientific community. <br/> <br/> Among these RCL sources, the Grande broadband source, a 9-lamp 1m diameter integrating sphere with a 25.4cm aperture and PTFE coating housed in a Class 10,000 cleanroom environment, is the workhorse for providing regular NIST traceable calibration services to ground, flight, and remote sensing missions on a consistent basis. <br/> <br/> As part of an initiative to improve the Grande calibration uncertainty budget, monitoring spectrometers were recently installed on Grande to provide continuous spectral radiance measurements of the integrating sphere source whenever Grande is in use. This monitoring data is used to characterize Grande’s ramp up stabilization and nominal operation process. Over multiple calibration sessions with Grande, we can observe long term source behavioral changes as the lamps age. <br/> <br/> Having continuous monitoring allows us to validate Grande’s stability during remote sensing calibration sessions. As stability data is accumulated and analyzed it results in updated and improved uncertainty budget for calibrations using Grande.