New Technological Solutions For Earth Observations Instruments With A Wide Field Of View

The improvements of the second-generation SPOT satellites increase Earth observation capabilities in three main ways: - the spectral range has been extended by adding a new infrared band to the HRV imaging instrument, now known as the HRVIR*, - the satellite's lifetime has been extended from 2.5 to 5 years, - the repetitivity of medium spatial resolution acquisitions has been increased by, adding "Vegetation", a new wide field of view instrument with the same spectral bands as the HRVIR. Its frequent image acquisi-tions can therefore be used to supplement the fewer observations made by the HRVIR. These improvements have been made to the SPOT 4 satellite which is to be launched in 1994. The first part of this article describes the main characteristics of the Vegetation payload's mission and gives a brief description of the payload itself. The second part looks at the payload's main sub-assembly, the imaging instrument. Like the HRVIR, this ins-trument has no constantly moving mechanical parts. The choice of a "static" solution (electronic scanning) for a wide field of view instrument has led us to conceive and develop (1) new technological solutions for the optical parts (2), a high-performance image electronics common to all spectral bands (3) and an onboard calibration device.