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The first of the latest batch of Galileo positioning satellites has passed initial tests in Holland, indicating that a launch this year for the much-delayed and over-budget European space project may still be possible.
The first of the 22 Full Operational Capability (FOC) satellites passed acoustic testing designed to simulate the conditions it will have to withstand during launch in “Europe’s largest sound system” at the European Space Agency’s ESTEC test centre in Noordwijk.
The Large European Acoustic Facility (Leaf) is an 11m wide, 9m deep, 16.4m high chamber with four noise horns embedded into the side of one wall. The Leaf’s walls are 0.5m-thick steel-reinforced concrete coated with thick epoxy resin to increase internal reverberation. The chamber is supported by rubber bearing pads to isolate it from its surroundings.
Noise is generated by passing a flow of nitrogen through the horns and is modulated to simulate the profile of the launch. The inert gas nitrogen is used so as to not harm the onboard systems of the satellite.
Galileo, also known as the European Global Navigation Satellite System, is already three times over its original target budget of €3 billion and nine years behind schedule. The project was first announced in 1999 with a completion date during 2008.
When fully operational by 2017, Galileo will be a system of 30 satellites orbiting at an altitude of 14,664 miles. It will be capable of locating any object on earth to within a distance of 4m. The projected 20-year cost of Galileo is said to be €22.2 billion. Each satellite has a planned lifetime of 12 years.
Georg Deutsch of European Test Services said: “The noise level reached during the test was 140.7dB, about the same noise as standing 25m away from a jet taking off.
“This involved a maximum liquid nitrogen flow of 3.5 to 4kg per second. Liquid nitrogen delivered by a tanker is vaporised to pass through the horns. More or less, we were able to finish the test campaign with one full tank of liquid nitrogen.”
The satellite is placed on a structure which includes air-based vibration isolators to ensure that vibration recorded by accelerometers fitted to it is from the sound and not resonance from the ground. Microphones placed around the satellite are used to check that the noise around the satellite is following the planned profile.
The 22 Galileo FOC satellites are functionally identical to the four validation satellites launched during 2011 and 2012, but with a higher transmit power. The FOC satellites have also been made by a different consortium which includes Germany-based OHB and UK-based Surrey Satellite Technology.
A 2013 launch for the first two FOC satellites was planned for September/October, but has been pushed back to December by the European Space Agency. Launches will only happen this year if both satellites pass a “system compatibility test campaign” that as well as acoustic testing includes thermal vacuum testing that simulates the conditions and temperatures of orbit.
Galileo will offer a freely available positioning and timing service like the US Global Positioning Satellites as well as more accurate services for military, civil security and commercial applications.