Galileo will consist of 30 satellites in medium Earth orbit supported by a global network of ground control and monitoring stations. A user with a receiver will be able to determine his or her position to within a few metres from signals broadcast by three or four of the satellites.

Work on new technologies needed for the constellation and the ground segment has been continuing apace at ESA's technical centre, ESTEC in the Netherlands.

Critical technologies include the development of on-board clocks for the satellites, signal generators to produce the variety of positioning signals that the Galileo spacecraft will broadcast; power amplifiers; antennae; timing units to correct the on-board clocks; and a system simulation facility to test strategies for coping with contingencies when the full system is up and running. In addition, ESA has started working on technologies needed for hand-held Galileo receivers.

Good progress has also been made with the first stage of the Galileo System Test Bed (GSTB) which allows engineers to validate Galileo-specific control algorithms, such as clock adjustments, and procedures for predicting individual satellite orbits, before the full system goes into operation. The second stage will allow critical technologies to be tested on satellites in medium Earth orbit.

The ESA and EU ministers are expected to confirm Galileo and to approve the Galileo development programme.

Related Links
Galileo website (European Commission)
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