The radiative transfer theory lies at the heart of optical remote sensing from space observations. It describes the physical processes characterising light propagation in the atmosphere and underlying surface. Advances in radiative transfer modelling increases our capability to detect and monitor changes in our planet through new scientific and technical approaches dedicated to the analysis and interpretation of measurements from space-borne radiometers. The scientific branch dedicated to measurements is called metrology.

Rayference uses radiative transfer modelling to improve the characterisation of space observations of the Earth. Metrology principles applied to space observations intensively rely on mathematical models that help us to understand how to design effective measurement systems, and to analyse the results they produce. A prominent example for a widely used guideline based on mathematical and statistical considerations is the Guide for the Expression of Uncertainty in Measurement (GUM) and its supplements. Mathematical techniques are used to develop and analyse idealized models of physical phenomena to be measured, and mathematical algorithms are necessary to find optimal system parameters. Finally, mathematical and statistical techniques are needed to transform the resulting data into useful information. The establishment of the necessary metrology infrastructure, tailored to climate needs in readiness for its use in climate observing systems, is one of the current challenges in the Earth Observation area. Radiative transfer modelling is a critical component of that system that secures an unbroken chain of uncertainty propagation for the calibration of space observations.

Rayference has been working on a series of projects related to the use of radiation transfer modelling to support calibration and validation activities, following metrological principles. The objective of the Metrology for Earth Observation and Climate (MetEOC) is to contribute to the establishment of the necessary metrology infrastructure, tailored to climate needs in readiness for its use in climate observing systems. Within this project, Rayference has established the needs in term of accurate 3D radiative transfer modelling and analysing the technical and scientific solutions to fulfil these needs. The development of the Eradiate model has been initiated in 2019 and will offer to the Earth Observation community a flexible framework for activities related with calibration and validation. This Open Source code will be publicly released end of 2021.

Rayference intensively benchmarks 1D radiative transfer models used to support calibration and validation activities. An example of such activity is the verification and correction of the S3A/SLSTR solar bands. This activity has been reported in web story of the Eradiate project entitled "Estimating the accuracy of 1D radiative transfer models over the Libya-4 site".

Do not hesitate to contact us for additonal information on our radiative transfer modelling activities.