2.1.5: SPOT and Helios

SPOT (Satellite Probatoire pour l'Observation de la Terre) was the first European (excluding Russian) remote sensing satellite, and the Helios spacecraft developed using the same bus was the first spy satellite from Europe. Spot 1 to 3 used the basic SPOT 1 bus, while SPOT 4 and Helios used an improved SPOT 4 bus.