Spot System Update

SPOT 1 AND 2

SPOT 1, launched back in 1986, is still orbiting the Earth and acquiring imagery long past its original two-year design life. It is now dedicated to seasonal data collection for European agricultural monitoring. SPOT 2 has been the primary global data collection platform since early 1990. In over seven years of uninterrupted service, SPOTs 1&2 have recorded almost three million images.

SPOT 3

SPOT 3 was successfully launched on September 25, 1993 at 9:45 EDT. Our third satellite is essentially the same as 1&2 in terms of basic design and capabilities. It is equipped with improved positioning instruments and modified onboard tape recorders. Two additional "passengers" on SPOT 3 include:

• POAM II: A US government experiment to measure ozone and aerosol concentrations over the poles. The Polar Ozone and Aerosol Measurement (POAM) payload is being managed by the US Office of Naval Research. The data will be made available to the international scientific community.

• DORIS: A precision orbit determination and radiopositioning system which measures Doppler shifts in radio signals transmitted by ground beacons. This will allow a determination of the satellite's position to within about 10 cm.

SPOT 4

SPOT 4 is currently being built and is scheduled for launch in 1997. Most notable among its new features will be: The addition of a mid-infrared band (1.58-1.75 um for vegetation studies and geologic application.

Onboard registration of all spectral bands, achieved by replacing the panchromatic sensor (0.51-0.73 um) with Band 2 (0.61-0.68 um) operating in both a 10- and 20-meter resolution mode.

• A larger capacity onboard recording system (40 min vs 22 min).

• Improved electrical and attitude control subsystems.

• A satellite data relay to system (Artemis) to complement the onboard tape recording system.

• An independent sensor called the (VMI) Vegetation Monitoring Instrument for large-scale oceanographic, vegetation, and global change studies. Characteristics are as follows:

- 2000 km wide swath for daily monitoring of the entire Earth

- Spatial resolution of 1 km

- High radiometric resolution with the following bands:

Blue .43-.47 m

Green .50-.59 m

Red .61-.68 m

Near Infrared .79-.89 m

Mid-Infrared 1.58-1.75 m