August 6, 2003

The life of a satellite

A satellite begins its life in space tucked inside the launcher fairing, which shields it from friction forces during ascent through the atmosphere. Mounted on a small attach fitting, it separates from the launcher by means of a pyrotechnic and spring-loaded release mechanisms on reaching its intended transfer orbit.

In the first hours after separation, the satellite deploys its solar panels, adjusts its attitude with respect to the Earth and Sun, and performs manoeuvres to reach its final orbit. These operations are part of the positioning phase, which varies according to the mission: in low-Earth orbit, the satellite is usually injected into an orbital trajectory near the intended orbit; in geostationary orbit, it is injected into a transfer orbit first.

At this stage in the mission, the satellite is not yet ready to begin routine operations. The in-orbit checkout phase is designed to validate system performance in a real operating environment, which is impossible to achieve on the ground. During this phase, the satellite’s instruments are progressively switched on and tested. At the end of in-orbit checkout, which may last weeks or months, the satellite is declared fit for service.

JASON-1 beginnings - video
(Windows Media Player)

On orbit, the satellite travels at a speed of 11,000 to 28,000 kilometres per hour, depending on its altitude. Various phenomena perturb its orbit, so it cannot hold its trajectory on its own. Stationkeeping operations, performed by ground controllers and the satellite’s onboard computer, make the necessary trajectory and attitude corrections throughout the mission to ensure that it continues to operate according to plan. 
Did you know?
Pre-launch tests
Ten hours before launch, telemetry from the satellite is sent to the operations control centre, where ground controllers keep a check on remotely measured parameters. They can thus prepare to control operations of equipment they will be monitoring during the mission.

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