Design of new photodiode standards for use in the MISR in-flight calibrator

The Multi-Angle Imaging SpectroRadiometer (MISR) is to be launched in 1998 as part of NASA´s Earth Observing System. The 3% (1σ) absolute radiometric calibration requirement for this instrument is considered challenging, particularly since it must be maintained through the five-year mission life. To meet this specification MISR will rely on detector-based calibration techniques, which are primarily founded on High Quantum Efficiency (HQE) detector technology. Filtered HQE photodiodes will be used to characterize solar-reflected light from a diffuse calibration target during the mission. In addition, radiation-hard photodiodes, which have an extended lifetime over the HQE detectors, will be utilized as part of the on-board calibrator. To date, flight photodiodes and filters have been fabricated, along with components of the photodiode flight package, and the photodiodes have undergone performance and stability testing. This paper gives a status report on these new in-flight photodiode standards, with primary emphasis on the photodiode performance measurements taken to date