SPOT is the French government sponsored civil Earth observation program, with support from Belgium and Sweden. A single SPOT satellite provides complete coverage of the Earth every 26 days. Image products from SPOT are handled by a commercial entity, SPOT-Image Corp. Spacecraft: 3-Axis stabilised. Single 5-panel solar array, each panel is 2.6 x 1.9 m. Hydrazine propulsion system provides orbit maintenance. Payload: Two HRVIR (High Resolution Visible - Infrared) push-broom imaging instruments are carried. HRVIR is derived from the HRV instruments on SPOT 1-3. This system will provide 10 m resolution in the panchromatic band and 20 m resolution in the multispectral bands. HRVIR includes a new medium IR channel to support vegetation analysis and harvest forecasting. The HRVIRs are steerable to within 27 deg off-nadir. Each HRVIR has a swath width of 60 km. The Vegetation Monitoring instrument has 1 km resolution in the same bands as the HRVIR. PASTEL optical link terminal supports laser crosslink experiments. DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) precision orbit determination system.
Financial/Operational:
Uses $ 110 million Silex - semiconductor laser intersatellite link experiment. Provides data relay for Artemis.

Design Life: 5 years . Total Length: 5.4 m. Maximum Diameter: 2.0 m. Total Mass: 2,755 kg.

Developed by Matra Marconi Space/Toulouse for CNES, the satellite provided 10-m resolution images with a wide field of view. SPOT 4 also carried a wide field 'vegetation' imager and a laser communications experiment. Launch was by an Arianespace Ariane 40 rocket, the base Ariane 4 model with no strap-on boosters. The liquid hydrogen fuelled third stage of the Ariane 40 entered an 800 km sun-synchronous orbit together with SPOT 4.

• 6 - JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. HTML when accessed: http://msl.jpl.nasa.gov/home.html