Galileo satellite arrives at ESA-ESTEC for testing

08/02/05

One of the two Galileo satellites currently under development, GSTB-V2/A, has arrived at ESA's European Space Research and Technology Centre to undergo testing.

Two satellites are being developed for the Galileo System Test Bed Version 2, which will make up the first phase of in the 'in-orbit validation' of the Galileo system. The primary mission of the first Galileo satellites is to secure the Galileo frequency filings, validate new technologies for operational use, characterise the radiation environment of the medium earth orbits that the operational satellites will occupy and enable experimentation with live Galileo signals.

Galileo is a global navigation satellite infrastructure under civil control. It is a joint initiative of the European Commission and ESA.

The satellite

The GSTB-V2/A spacecraft is being developed by Surrey Satellite Technology Ltd (SSTL), based in The United Kingdom. It is a 3-axis stabilized satellite with a body measuring 1.3 m 1.8 m 1.65 m and it has a lift-off mass of about 600 kg. Seven hundred Watts of electrical power will be provided by two sun-tracking solar arrays each 1.74 m long when deployed.

The satellite will carry a payload that will transmit a Galileo experimental signal. Main elements of the payload are:

  • An antenna, comprising a phased array of individual L-band elements, illuminating all the visible Earth below the satellite
  • Two signal generation units, one able to generate a simple Galileo signal, and the other able to generate more representative Galileo signals
  • Two Rubidium atomic clocks
  • The expected satellite lifetime is two years.

    Test campaign

    ESA maintains a large centre for the testing of space vehicles and their subsystems at its European Space Research and Technology Centre (ESTEC), located at Noordwijk in The Netherlands. The ESTEC Test Centre has the capability of simulating the conditions that spacecraft will experience during launch and once they are in space. ESA will conduct the GSTB-V2/A testing on behalf of the spacecraft manufacturer.

    The tests that GSTB-V2/A will undergo include:

  • Space environment simulation the satellite will be placed in ESTEC's Large Space Simulator (LSS), where its performance in the cold and vacuum of space can be assessed.
  • Solar array deployment the solar arrays will be unfolded to confirm correct functioning of the deployment mechanisms and the systems that keep them stowed during launch.
  • Shock and vibration the spacecraft will be subjected to vibration and mechanical shocks during launch and separation from the launcher. An electrodynamic shaker will simulate this environment to ensure that the satellite can withstand it.
  • Acoustic at lift-off and during the early part of its journey into space, the satellite is exposed to intense noise. The Large European Acoustic Facility will simulate this environment to check that the spacecraft will not be damaged by the noise.
  • Electromagnetic compatibility to ensure that the various spacecraft systems do not affect one another's correct functioning through radio signals emitted intentionally or by electrical interference
  • GSTB-V2/A has had the instrument sensors needed for the first sequence of tests installed and it has been placed in the LSS ready for the start of thermal vacuum and thermal balance testing.

    The future

    The other of the two Galileo satellites, GSTB-V2/B, made by the European consortium Galileo industries, is currently being assembled and tested at the premises of Alenia Spazio in Rome, prior to moving to ESTEC for final testing in the autumn.

    The first Galileo launch is scheduled for December this year. The satellite will be carried into space from the Baikonur cosmodrome in Kazakhstan by a Soyuz launcher.

    Source: Eurekalert & others

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