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Radiometric inter-sensor cross-calibration uncertainty using a traceable high accuracy reference hyperspectral imager

Gorrono, J; Banks, A C; Fox, N P; Underwood, C (2017) Radiometric inter-sensor cross-calibration uncertainty using a traceable high accuracy reference hyperspectral imager. ISPRS Journal of Photogrammetry and Remote Sensing, 130. pp. 393-417.

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Satellite borne earth observation (EO) optical and infrared sensors generally suffer from drifts and biases relative to their pre-launch calibration. These can be due to the launch itself and/or time in the space environment. This places a severe limitation on the fundamental reliability and accuracy that can be assigned to satellite derived information where this aspect is critical particularly, for example, in long time base studies for climate change. The proposed TRUTHS (Traceable Radiometry Underpinning Terrestrial and Helio-Studies) mission is explicitly designed to address this issue through re-calibrating itself directly to a primary SI standard in-orbit and then through the extension of this SI-traceability to other sensors through in-flight cross-calibration. Where the characteristics of the sensor under test allows, this could result in a significant improvement in accuracy. This paper describes a set of tools, algorithms and methodologies that have been developed and used in order to estimate the radiometric uncertainty achievable for an indicative target sensor through in-flight cross-calibration using a well-calibrated hyperspectral SI-traceable reference sensor with observational characteristics such as TRUTHS. In this study, a Sentinel-2 Multi-Spectral Imager (MSI) or Landsat-8 Operational Land Imager (OLI) like sensor is evaluated as an example, however the analysis is readily translatable to larger footprint sensors such as Sentinel-3 Ocean and Land Colour Instrument (OLCI) and Visible Infrared Imaging Radiometer Suite (VIIRS). This study considers the criticality of the instrumental and observational characteristics and uses the Committee on Earth Observation Satellites (CEOS) recommended Libya-4 Pseudo Invariant Calibration Site (PICS) as a demonstration vicarious ground site. The analysis is performed on pixel level reflectance factors, within a defined spatial region of interest (ROI) within the target site. It quantifies the main uncertainty contributors in the spectral, spatial, and temporal domains. The resultant tool will support existing sensor-to-sensor cross-calibration activities carried out under the auspices of the Committee on Earth Observation Satellites (CEOS), but is also being used to inform the design specifications for TRUTHS.

Item Type: Article
Keywords: TRUTHS, inter-sensor cross-calibration, Libya-4, Pseudo Invariant Calibration Site (PICS), radiometric uncertainty.
Subjects: Optical Radiation and Photonics > Environment and Climate Change
Divisions: Chemical, Medical & Environmental Science
Identification number/DOI: 10.1016/j.isprsjprs.2017.07.002
Last Modified: 06 Feb 2018 11:56
URI: http://eprintspublications.npl.co.uk/id/eprint/7680

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