SPOT 4 OVERVIEW
SPOT 4 is considered a 2nd generation SPOT series satellite from CNES.
The most important advance was the addition of the “Vegetation” instrument, with four spectral bands to allow continuous, worldwide crop monitoring. The data would be used for crop forecasts and environmental studies.
The SPOT 4 design differed from the earlier SPOT series (SPOT 1,2,3) in the following aspects:
- five years design lifetime instead of three
- a new extended platform design, the SPOT 4 satellite bus referred to as SPOT MK2, and service module are employed accommodating twice the payload of the former SPOT 3 bus
The spacecraft was three-axis stabilised. Attitude was sensed by an inertial platform consisting of four rate gyros, two digital Earth sensors, and two digital sun sensors.
SPOT 4 offered increased onboard storage capacity (from 22 minutes to 40 minutes, corresponding to 240 Gbit). A 10 Gbit solid-state memory was added to increase the overall onboard recording capability.
|Dimensions||2 m x 2 m x 5.6 m|
|Design lifetime||5 years|
SPOT 1 through to SPOT 5 had identical Sun-synchronous circular orbits with an altitude of 832 km. The repeat cycle was 26 days with just over 14 orbits per day.