Activités

The CTOH provides these various users with expertise in the physics of altimetric measurement in a continental context, software for the simulation and processing of altimetric measurements and new space hydrology products.

 

The CTOH is very involved in the scientific definition and calibration phases for new missions using nadir or LRM (Low Resolution Mode) altimetry or wide-swath altimetry, which will be tested for the first time on the Surface Water and Ocean Topography (SWOT) mission. It is also involved in efforts to improve the quality of data from past altimetry missions in order to obtain long times series of data that are as uniform as possible in terms of the processing applied to the observations.

 The CTOH has developed corrections for altimetric measurements specific to continental surfaces and has reprocessed all of the radar echoes from the European Space Agency’s (ESA) ERS-2 mission with adapted algorithms for monitoring continental surfaces and polar ice caps.

The resulting product has characteristics similar to the latest version of data from Envisat, a satellite travelling in the same orbit as its predecessor ERS 2 (Figures below).
ERS2_ctoh_mean_sig0_ice1_world ERS2_ctoh_std_sig0_ice1_world

 

The team has also developed an altimeter radar echo (or waveform) simulator. In complex and highly irregular environments such as continental surfaces, electromagnetic modelling offers a clearer understanding and helps correct some of the errors that can interfere with the reconstruction of water levels based on altimeter measurements.

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These data sets are a unique source of information that can be used to measure interannual variations in the amount of water at the surface. They also prefigure the data that will be provided by the future SWOT mission, a joint development by CNES and NASA that should be launched around 2020.

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