Abstract
We propose a space benchmark sensor with onboard SI (Système International) traceability by means of quantum optical radiometry. Correlated photon pairs generated by spontaneous parametric down-conversion (SPDC) in nonlinear crystals are used to calibrate the absolute responsivity of a solar observing radiometer. The calibration is systematic, insensitive to degradation and independent of external radiometric standards. Solar spectral irradiance at 380–2500 nm is traceable to the photon rate and Planck’s constant with an expected uncertainty of about 0.35%. The principle of SPDC calibration and a prototype design of the solar radiometer are introduced. The uncertainty budget is analyzed in consideration of errors arising from calibration and observation modes.
Highlights
Space radiometric benchmarks were proposed in recent years to reveal the trend of climate change and evaluate the energy budget of the Earth system with high confidence [1,2,3,4]
In comparison with the effort that traces the solar spectral irradiance to optical power measured by an onboard electric substitute radiometer [32], we suggest a tracing chain that links solar spectral irradiance to photon rate and Planck’s constant, by means of spontaneous parametric down-conversion (SPDC)-based detector calibration described in the previous section
A solar spectral irradiance radiometer integrated with a quantum optical standard is proposed for a future space benchmark
Summary
Space radiometric benchmarks were proposed in recent years to reveal the trend of climate change and evaluate the energy budget of the Earth system with high confidence [1,2,3,4]. Space benchmark sensors are expected to measure solar total irradiance, solar spectral irradiance and Earth reflective radiance with uncertainties of about 0.02%, 0.2% and 1%, respectively [1,2,3,4], comparable to the highest accuracies currently achievable in national metrology labs These stringent requirements of uncertainties cannot be satisfied with traditional traceability chains connecting space sensors to laboratory radiometric standards [3]. Several approaches have been developed to monitor and assess the degradation of space-borne solar instruments and there is no single best method, but rather a combination of methods taking into account the applicability to the mission targets and the instrumental design [8] In another respect, operating an onboard calibrator with climate accuracy for every sensor may result in unacceptable engineering complexity and expenses.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
