The satellites SPOT 4 (Satellite Probatoire de l'Observation de la Terre) was a second generation of SPOT earth observation satellite operated by Spot Image.
SPOT 4 used the improved bus design, which differed from the earlier SPOT series by having an increased lifetime of five years instead of three, a new extended platform design and service module, which can accommodate twice the payload. The propulsion module consists of a frame made of aluminum bars and two capillary tanks holding 158 kg of hydrazine.
The prime imaging instrument was HRVIR (High-Resolution Visible and Infrared sensor), which consisted of two pushbroom imaging units, an improved version of HRV. The two spectral modes are panchromatic and multispectral. The panchromatic band had a resolution of 10 meters, and the three multispectral bands (G,R,NIR) have resolutions of 20 meters.
An additional sensor for SPOT-4, called Vegetation or VMI (Vegetation Monitoring Instrument), with a ground… read more