Development of Self-Calibration Spectral Radiometer of Correlated Photons on Orbit

Optical sensor on orbit is usually calibrated by on-board calibrator or some astronomical objects such as moon, sun or other stars in the visible and near infrared band, primary standard and standard transfer train are the most important sources of uncertainty during the process of calibration . Currently many satellite’s calibrators are needed to be installed on orbit. Calibrator can be used to calibrate satellite sensor periodicity, it is helpful to improve the quality of science data products derived from sensor observations, but it’s difficult to evaluate itself change of calibrator, calibration accuracy on orbit is difficult to less than 3%.A new self-calibration spectral radiometer of correlated photons is developed based on spontaneous parametric down-conversion (SPDC) effect, including radiometric observation and self-calibration mode, radiometric observation can be used to measure radiance of optical sensor and transfer to other satellite sensor using cross calibration method. Self calibration mode can calibrate response change of optics and electronic on orbit and modify calibration coefficient of optical sensor periodicity, compared with other calibration method on orbit, correlated photons is absolute and not dependent on primary standard and standard transfer train, only by measuring the ratio of the number of coincidence events to the number of trigger detection, trigger channel optical transmittance, the quantum efficiency of trigger detector is not need to be konwn.Principle of the new spectral radiometer is introduced, optics system of eight channel radiometer is designed, electronic and signal processing is analysed. ICMOS low light sensor is used to observe of space and spectral distribution of correlated photons, some measurement results are introduced in detail, its uncertainty is assessed, combine uncertainty is less than 0.35%. It is hopeful that the self-calibration spectral radiometer will be used in the fields of on-orbit calibration, cross calibration of other satellite sensor, field observation instrument calibration and climate change observation in future, etc.