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Contents GIOVE-AGIOVE-BGIOVE-A2About Galileo What is Galileo?Why Europe needs GalileoWho's involved in Galileo?Galileo technology developmentsHow to build up a constellation of 30 navigation satellites Galileo Documentation Resources Development FacilitiesGalileo system simulation facilityMultimedia Image galleryVideo galleryRSS feeds Screensavers & WallpapersMedia Centre Press ReleasesServices Calendar
| | | | | | | | | GIOVE-A satellite (artist's impression) | |
First satellites: Galileo In Orbit Validation Element / GIOVE
Three experimental Galileo satellites - GIOVE-A, GIOVE-B and GIOVE-A2 are part of the first step in the in-orbit validation of the Galileo system. GIOVE-A was orbited by a Soyuz launcher from the Baikonur cosmodrome on 28 December 2005.
GIOVE-B is scheduled to be launched end of 2007. GIOVE-A2 has been ordered to be ready for launch in the second half of 2008. The actual launch date of this satellite will be decided later, taking into account the situation of GIOVE-A and GIOVE-B.
The launch of the test satellites for Galileo represents some major achievements:
- the first time Europe has flown a navigation satellite
- the first time Galileo signals have been transmitted from Space
- the first time Europe has flown a satellite in Medium Earth Orbit (MEO)
- Europe is meeting the requirements for the Galileo frequency filing
- the hydrogen maser clock will be the most accurate clock ever flown in space
| | | GIOVE-A structural model |
GIOVE-A
GIOVE-A was developed by Surrey Satellite Technology Ltd (UK). This first mission for a Galileo satellite is a complete success, with the achievement of all its objectives:
- securing the frequency filings with ITU: frequencies were brought into use on 3 March 2006
- validation of key technologies - all performing largely in line with expectations for the different elements such as the new rubidium clocks
- facilitating the experimental reception of navigation signals from Medium Earth Orbit (MEO) - using two transmission channels in parallel
- characterisation of the MEO environment using two different radiation monitoring instruments
This 3-axis stabilized satellite has a cubical body of 1.3 m x 1.8 m x 1.65 m with a lift-off mass of 600 kg and a power demand of 700 W provided by two wings of sun-tracking solar arrays each 1.74 m long. The satellite uses a butane propulsion system with two tanks containing 25 kg each.
The satellite carries a payload that transmits a Galileo experimental signal in two separate frequency channels. The main elements of the payload are:
- the antenna: a phased array of individual L-band elements, illuminating all the visible Earth below the satellite
- the signal generation units: two sets, one able to generate a simple Galileo signal, and another one, able to generate more representative Galileo signals
- the clocks: two redundant, small-size Rubidium atomic clocks with a stability of 10 nanoseconds per day
The expected satellite lifetime is 2 years.
| | | GIOVE-B satellite (artist's impression) |
GIOVE-B
The GIOVE-B satellite is being developed by European Satellite Navigation Industries (formerly Galileo Industries), a European consortium including Alcatel Space Industries (F), Alenia Spazio (I), Astrium GmbH (D), Astrium Ltd (UK) and Galileo Sistemas y Servicios (E).
GIOVE-B is intended to fulfil similar objectives to GIOVE-A: securing frequency filings, expanding the technologies experimentation to include the passive hydrogen maser clock, characterisation of the MEO orbit using one radiation monitoring instrument, improved signal transmission capabilities using 3 channels in parallel, and enabling expanded signal experimentation.
This is a 3-axis stabilized satellite, with stowed dimensions (with the solar arrays folded) of 0.95 m x 0.95 m x 2.4 m. It will have a lift-off mass of 523 kg and will be equipped with two solar array wings each 1.49 m long supplying up to 700 W of power.
The satellite will use a hydrazine propulsion system with one tank containing 28 kg.
The satellite will carry a payload that will transmit a Galileo experimental signal on three separate frequency channels. The main elements of the payload are:
- the antenna: a phased array of individual L-band elements, illuminating all the visible Earth below the satellite
- a navigation signal generation unit with significant flexibility to generate different types of signals
- the clocks: one small size rubidium atomic clock with a stability of 10 nanoseconds per day, and a larger passive hydrogen maser clock, another type of atomic clock with better stability (1 nanosecond per day) and which will be the most stable clock ever flown in space
The expected satellite lifetime is 2 years.
GIOVE-A2
GIOVE-A2 is a development of GIOVE-A and is also being manufactured by Surrey Satellite Technology Ltd (UK). The new satellite will incorporate some enhancements over GIOVE-A which will allow additional signals to be generated and received on the ground.
The aim will be to provide early in-orbit experimentation with the common baseline L1 open service signals recommended by the European Union and the United States. In the future, these open service signals will provide free of charge position and timing competitive with other GNSS systems.
GIOVE-A2 is meant to maintain the International Telecommunications Union (ITU) frequency filing that was secured by its predecessor and facilitate further development of ground equipment, should anything happen to GIOVE-A or B, since ITU regulations do not allow a broadcast gap of more than two years. Therefore, the timing of the GIOVE-A2 launch will depend on the situation of GIOVE-A and GIOVE-B.
ESA wishes to guarantee the continuity of the Galileo programme with the permanent presence of a spacecraft in orbit. This will maintain European rights to the frequencies and allow continuation of the experiments initiated with the successful GIOVE-A mission and planned for the upcoming GIOVE-B satellite.
Last update: 16 August 2007 | |
| | First stages of Galileo Galileo testbedsFirst two satellitesFrequency filingsIn-orbit validation OverviewIn-orbit validation system: the first 4 satellitesFull deployment OverviewThe constellation: 27 satellites + 3 in reserveGalileo systemGalileo specifications Galileo signals and frequenciesHow do the Galileo clocks work ?ReceiversServicesRelated Sites Galileo website (European Commission)European GNSS Supervisory Authority (GSA)European Satellite Navigation IndustriesGPSGLONASSCENC
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