One year of support to CNES missions
End of November 2023, HYGEOS started number of studies to support CNES in the calibration, validation and data processors development for current and future spatial missions. One year later, many results have been obtained.
In preparation of the TRISHNA mission to be launched in 2026:
- Masks of cloud probabilities, using the thermal infrared spectral bands of the TRISHNA thermal sensor have been developed. The main cloud mask is a statistic Bayesian mask, similar to the one applied on Sentinel-3 SLSTR images. Others masks have also been developed based upon innovative methods like the artificial intelligence and the machine learning. The Bayesian mask is the prime candidate for further implementation into the Level 2A operational processing chain retrieving Land Surface Temperature, due to its best performances and it more advance maturity. Next steps are the fine-tuning of mask parameters and probability thresholds and the prototyping of the methodology.
- The performance of the algorithm DirecTES, retrieving the Land Surface Temperature (LST) assuming the state of the atmosphere is known, has been evaluated over land. An improvement of the algorithm (DirecTES V2) has been proposed allowing to retrieve systematically the LST over 100% of the pixels, which is not the case of the original version.
- Three approaches have been investigated to retrieve the surface temperature over water. Since they give similar results, the simple inversion of Top-Of-Atmosphere radiances is recommended because it is less processing time consuming than DirecTES.
- The software of DirecTES has been updated, especially regarding the update and improvement of the ancillary data (atmospheric coefficients corrected from surface pressure and water vapour content, cloud and water masks, …).
A significant upgrade, called SMAC-NEO, of the SMAC code has been developed. In addition to the algorithmic improvements, like a new calculation of the gaseous absorption, SMAC-NEO includes robust and powerful software enhancements leading to a more generic and automated tool.
A CIMEL CE312 radiometer, installed on the La Crau calibration site, collects in-situ data. The data are processed with an existing prototype. HYGEOS has investigated many options to improve the aerosols characterisation, especially the refractive index, and the estimate of gas content (O2, H2O, CH4, CO2, O3). The most promising is the implementation of the GRASP-OPEN code to exploit the data of a hyperspectral CIMEL instrument currently in development.