GOCE Satellite Blasts Off

By Douglas Barrie

The European Space Agency's Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite was launched March 17 aboard a Russian Rockot launch vehicle from Plesetsk Cosmodrome, following a 24-hour hold.

The hold on the previous day - with seven seconds left on the clock - was due to an issue with an element of the launch platform. The overall GOCE program is well behind the original schedule.

The satellite will be checked out over the next six weeks, following which GOCE will then be moved to its operational orbit at an altitude of 263 kilometers (164.3 miles). This will be followed by a further six weeks of work on the payload to ensure its correct operation, due to start in the early summer.

GOCE's main payload is an electrostatic gravity gradiometer that will provide the raw data to generate an accurate map of Earth's gravitational field. It will also help more accurately model sea-level changes.

To gain the best performance from the gradiometer, GOCE will operate at an altitude where it will encounter significant atmospheric drag. This was a design driver for the satellite's aerodynamic shape.

It is also fitted with two ion engines - one primary and a backup. The engine will be used to provide near real-time corrections for atmospheric drag. Were both engines to fail, GOCE would have about 10 days before its orbit decayed irrevocably.

GOCE launch photo: NASA