Abstract
The Sea and Land Surface Temperature Radiometer (SLSTR) on the Copernicus Sentinel-3 mission is a dual-view, multi-channel scanning radiometer specifically designed to measure global sea-surface temperatures SST to an uncertainty < 0.3K for climate monitoring and continue the 21 year datasets of the Along Track Scanning Radiometer (ATSR) series. Two instruments were originally planned with the first being launched in February 2016 and the second launch schedule for spring 2018 to provide daily global coverage of SST and LST data. A further two instruments are being developed as replacements when the first two reach the end their operational lifetime.
Thorough pre-launch calibration using accurate sources and agreed procedures is a fundamental prerequisite for ensuring traceability and consistency of the data generated by the two instruments. This is particularly important at thermal infrared wavelengths where verification of the calibration against traceable reference standards becomes very difficult once on orbit.
The SLSTR-A and B instruments underwent extensive pre-flight calibration campaigns to ensure that all the necessary calibration parameters are measured before launch, but more importantly that the end-to-end system performance and calibration model is fully verified against traceable calibration sources before launch. As an infrared sensor, this is essential for understanding all sources of uncertainty that affect the instrument calibration which cannot be directly measured once on-orbit.
The pre-launch calibration activities included the spectral response characterisation, instrument line-of-sight for verification of the geometric pointing model, solar channel radiometric and thermal infrared radiometric calibration. A purpose built calibration rig was developed to provide a controlled thermal environment necessary for thermal infrared wavelengths and to allow the blackbody calibration sources around the field of view of the instrument. In the paper, the authors describe the test methods and measurement results and compare the results between the two models. Results from the model A instrument were used to improve methods used for the model-B instrument. In particular, additional tests and improvements to the test setup for the visible and short-wave infrared calibration activities have shed light on results from the model-A instrument.
Pre-Launch Calibration of the Sea and Land Surface Temperature Radiometer
The Sea and Land Surface Temperature Radiometer (SLSTR) on the Copernicus Sentinel-3 mission is a dual-view, multi-channel scanning radiometer specifically designed to measure global sea-surface temperatures SST to an uncertainty < 0.3K for climate monitoring and continue the 21 year datasets of the Along Track Scanning Radiometer (ATSR) series. Two instruments were originally planned with the first being launched in February 2016 and the second launch schedule for spring 2018 to provide daily global coverage of SST and LST data. A further two instruments are being developed as replacements when the first two reach the end their operational lifetime.
Thorough pre-launch calibration using accurate sources and agreed procedures is a fundamental prerequisite for ensuring traceability and consistency of the data generated by the two instruments. This is particularly important at thermal infrared wavelengths where verification of the calibration against traceable reference standards becomes very difficult once on orbit.
The SLSTR-A and B instruments underwent extensive pre-flight calibration campaigns to ensure that all the necessary calibration parameters are measured before launch, but more importantly that the end-to-end system performance and calibration model is fully verified against traceable calibration sources before launch. As an infrared sensor, this is essential for understanding all sources of uncertainty that affect the instrument calibration which cannot be directly measured once on-orbit.
The pre-launch calibration activities included the spectral response characterisation, instrument line-of-sight for verification of the geometric pointing model, solar channel radiometric and thermal infrared radiometric calibration. A purpose built calibration rig was developed to provide a controlled thermal environment necessary for thermal infrared wavelengths and to allow the blackbody calibration sources around the field of view of the instrument. In the paper, the authors describe the test methods and measurement results and compare the results between the two models. Results from the model A instrument were used to improve methods used for the model-B instrument. In particular, additional tests and improvements to the test setup for the visible and short-wave infrared calibration activities have shed light on results from the model-A instrument.