Sentinel-2 diffuser on-ground calibration
2013
The Sentinel-2 multi-spectral instrument (MSI) will provide Earth imagery in the frame of the Global Monitoring for
Environment and Security (GMES) initiative which is a joint undertaking of the European Commission and the Agency.
MSI instrument, under Astrium SAS responsibility, is a push-broom spectro imager in 13 spectral channels in VNIR and
SWIR. The instrument radiometric calibration is based on in-flight calibration with sunlight through a quasi Lambertian
diffuser. The diffuser covers the full pupil and the full field of view of the instrument. The on-ground calibration of the
diffuser BRDF is mandatory to fulfil the in-flight performances.
The diffuser is a 779 x 278 mm 2 rectangular flat area in Zenith-A material. It is mounted on a motorised door in front of
the instrument optical system entrance. The diffuser manufacturing and calibration is under the Centre Spatial of Liege
(CSL) responsibility.
The CSL has designed and built a completely remote controlled BRDF test bench able to handle large diffusers in their
mount. As the diffuser is calibrated directly in its mount with respect to a reference cube, the error budget is significantly
improved. The BRDF calibration is performed directly in MSI instrument spectral bands by using dedicated band-pass
filters (VNIR and SWIR up to 2200 nm). Absolute accuracy is better than 0.5% in VNIR spectral bands and 1% in SWIR
spectral bands. Performances were cross checked with other laboratories.
The first MSI diffuser for flight model was calibrated mid 2013 on CSL BRDF measurement bench. The calibration of
the diffuser consists mainly in thermal vacuum cycles, BRDF uniformity characterisation and BRDF angular
characterisation. The total amount of measurement for the first flight model diffuser corresponds to more than 17500
BRDF acquisitions.
Performance results are discussed in comparison with requirements.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
0
References
3
Citations
NaN
KQI