Digital twin of satellite observation of the Earth – RT-Twin

The objective of LabCom RT-Twin is to improve the work in the field of Earth observation (i.e., remote sensing), such as the preparation of space missions and the exploitation of measurements from existing observation systems. The approach is based on the physical modelling of remote sensing measurements, in particular with the three-dimensional (3D) radiative transfer (RT) model DART (https://dart.omp.eu) developed at CESBIO. DART has now reached a level that allows accurate and efficient simulation of remote sensing measurements of natural and urban landscapes, for any observation configuration (viewing direction, spatial resolution, spectral resolution, any altitude, etc.), from ultraviolet to thermal infrared, including LiDAR signal and solar-induced chlorophyll fluorescence (SIF). In addition, CNRS certified DART on July 2023, and Toulouse III University already delivered more than 600 DART licences to scientists. The aim is to take advantage of the scientific progress in TR modelling made by the DART team at CESBIO, to consolidate DART, adapt it to the needs of ACRI-ST and thus improve the potential of ACRI-ST in the field of Earth observation. ACRI-ST and CESBIO have collaborated several times for the optimization of Earth Observation missions with DART. This joint work has confirmed the validity and the need to create a common laboratory to progress in the transformation of the DART model into an operational tool for a wider audience (scientists and technicians of Earth observation). This approach ensures the valorisation of DART. It is a two-way process: ACRI-ST will benefit from CESBIO's expertise on the DART tool to jointly enhance its use, and CESBIO will benefit from an ideal context to maintain and "keep alive" DART in its scientific excellence, in a very competitive environment. These joint benefits are naturally built on an iterative approach between the activities of the two entities.

Two areas in particular are being considered for this joint laboratory:
1) DART enhancement:
- TR modeling in DART for operational simulation (i.e., computation time, memory space) of realistic and physically correct images of natural and urban landscapes.
- Landscape models and landscape elements (e.g., house, tree, plant) used by DART, with in particular georeferencing of DART models and products and coupling with plant growth models, and operational parameterization of the atmosphere.
- Propagation of uncertainties within DART due to unavoidable uncertainties concerning in particular the optical properties of landscape elements.

2) Valorization of research work:
- Preparation / pre-dimensioning of new space missions, with evaluation of their performance, based on DART simulations.
- Qualification of new processing algorithms on reference landscape simulations, and support for validation activities and space applications.
- Promotion of developments with an on-demand image generation and expertise service for space industry players.
- Promotion and valorization of developments within the framework of institutional space missions and/or the NewSpace ecosystem.