How to navigate satellites launched into space

ESA's most modern navigation satellite launched at night

27/04/2008623 views0 likes

ESA PR 25-2008 Last night, with the launch of the second ESA satellite for orbital validation of Galileo (GIOVE), another step was taken towards the realization of Europe's satellite navigation system.

GIOVE-B, which carries the most precise atomic clock ever launched into space, took off this morning at 4:16 a.m. local time (00:16 a.m. CEST) on board a Starsem-operated Soyuz / Fregat carrier from the Baikonur Cosmodrome in Kazakhstan and was first promoted to medium earth orbit. The Fregat upper stage was then used: after a series of maneuvers, it finally reached a circular orbit at an altitude of around 23,200 km with an inclination of 56 ° to the equator, on which it placed the satellite around 3 hours and 45 minutes after takeoff safely suspended. The two solar cell wings that supply GIOVE-B with electricity unfolded correctly and were fully operational at 05.28 a.m. CEST.
The 500 kg satellite was built by a European industrial consortium under the direction of Astrium GmbH; Thales Alenia Space was responsible for the integration and testing in Rome. Two years after the hugely successful GIOVE-A mission began, this new satellite will continue to demonstrate critical technologies for the navigation payload of the future Galileo operational satellites.

Three high-precision space clocks on board

Like its predecessor, GIOVE-B also has two small rubidium atomic clocks with a stability of 10 nanoseconds per day as a reserve. Even more precise, however, is its passive hydrogen maser (PHM), which has a stability of less than 1 nanosecond per day. With> GIOVE-B, an atomic clock of this type was launched into space for the first time; the most precise space clock to date is now in orbit. Each Galileo operational satellite will have two PHMs as primary clocks and two spare rubidium clocks on board.
GIOVE-B also carries a payload for radiation monitoring, which is to investigate the space environment at the altitude at which the Galileo constellation will be used, and a laser retroreflector for high-precision position determination using laser beams.
The representative Galileo signals produced by signal generation units are broadcast on three different frequencies via a phase-controlled group antenna in the L-band, which is intended to cover the entire part of the earth visible under the satellite.
GIOVE-B is now under the control of Telespazio's satellite operations center in Fucino, Italy and verification of the satellite in orbit has begun.

Final demonstration in front of Galileo

In addition to its technology demonstration mission, GIOVE-B will also take on GIOVE-A's task of securing the frequencies for Galileo, as the first Galileo demonstration satellite, which was launched in December 2005, is slowly reaching the end of its service life.
The next step after GIOVE-B will be the launch of four operational satellites to validate the Galileo space and the associated ground segment in 2010 at the latest. As soon as this orbital validation (IOV) phase is completed, the remaining satellites will be launched and placed in their orbit to bring 30 identical satellites into full operational readiness (FOC).

"With the launch of GIOVE-B we are close to the end of the demonstration phase for Galileo," said ESA Director General Jean-Jacques Dordain in Fucino, when he congratulated the ESA and industry teams. “The close cooperation between ESA and the European Commission has been crucial for our progress in the difficult environment of recent years. Despite these difficulties, Galileo is already a reality with two satellites in orbit, significant progress on the next four (they are already in the construction phase) and a fully qualified EGNOS service * - all at the service of citizens in Europe and around the world . The ESA will shortly initiate the procurement for the entire constellation according to the IOV under the responsibility of the European Commission. "

With Galileo, Europe will have its own global satellite navigation system that is under civilian control and will offer a highly accurate, guaranteed global positioning service. It will be interlinked with the other two existing global satellite navigation systems, the US Global Positioning System (GPS) and the Russian GLONASS system. Galileo will transmit location signals with an accuracy of 1 meter in real time with unprecedented integrity.

* Note for editors: The European Geostationary Navigation Overlay Service (EGNOS) is a joint program of the European Space Agency, the European Commission and Eurocontrol. It comprises a network of more than forty systems across Europe that collect, store, correct and improve data from the American GPS. The changed signals are then sent to the user terminals via geostationary satellites, which leads to a positioning accuracy of less than 2 meters compared to the original GPS accuracy of 15 to 20 meters. In addition, unlike GPS, EGNOS offers a signal quality guarantee.
For more information:
ESA communications department
Media Relations Unit
Tel .: + 33 (0) 1 53 68 72 99

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