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Mesures physiques et signatures en télédétection

Centre National d'Etudes Spatiales
Programme Directorate/Earth Observation
18 avenue E. Belin
31055 TOULOUSE Cedex
* 2 place Maurice Quentin
75001 PARIS cedex 02
The French Programme for Earth observation aims at providing remote sensing data for reserach or
applications in the domains of atmosphere, ocean or land. It is conducted in the framework of bilateral
cooperations or within the European Space Agency optional programme. Its main axis is to set up or maintain
series of instruments to offer a continuity in the data for a long tune. The SPOT programme, with SPOT2 and 3
presently operational, will be purshued with SPOT-4 launched in 1997 wich will exhibit several improved
capabilities for vegetation studies (HRVTR with an additional channel at 1.6 pm). In particular the wide field of
view VEGETATION instrument will permit a daily global observation at 1km resolution, in channels similar to
HRVIR. The SPOT-5 satellite presently under study will have a higher spatial resolution and an adavanced
stereoscopic capability.
Experimental systems are also planned in a near future or still under study. POLDER onboard ADEOS
japenese satellite will permit studies of polarized bidirectional signatures of terrestrial targets. In addition,
IRSUTE, a high spatial resolution multichannel thermal infrared radiometer to be embarked onboard a small
satellite will be studied in 1994. . All these systems are presented with a description of the specified
performances and the main products expected.
In the domain of vegetation monitoring the main scientific objectives belong to the following categories :
- land use mapping :
• for surface estimates in agriculture, but also for land cover change monitoring, local environment
monitoring (fires.etc.),etc.
• for derivation of maps of model parameters (i.e Phulpin et al, 1988)
- estimation of quantitative products. They are :
• the Net Primary Production (NPP), giving access to crop yields, pastures or timbers productions.etc.
• descriptors of vegetation functioning for a better understanding of the connexions between vegetation and
• the fluxes of matter (water, carbon, nitrogen, etc.) and energy (Rn, LE, H,etc.) between ground , vegetation
and atmosphere. This could find applications in meteorology (refining the water cycle description in
mesoscale to global scale models), in hydrology or agriculture (water management).
These products may be accessible directly or through the determination of physical variables whose values can
be more or less validated by means of ground truth. They are for instance : total biomass, vegetation height,
average leaf area index, fractional cover, APAR, Surface Temperature, surface Humidity, roughness,etc. These
physical variables are inputs of models predicting crop production (i.e Maas, 1988), or of ecophysiologic
models (i.e Running et al, 1989 ), these being fed with other kinds of data (meteorological network data,
information on water management, on agricultural process, DEM, etc.) which are essential to optimize the use
of satellite data.
Two categories of users can be distinguished :