Galileo-Navigationssystem

Earlier this week, GIOVE-A successfully transmitted its first navigation message, containing the information needed by user receivers to calculate their position. Prior to reaching this milestone, the satellite had been broadcasting only the data needed for measuring the receiver-to-satellite distance.
 
The first Galileo navigation message was created by the navigation signal generator unit on board GIOVE-A, using content prepared by the GIOVE Mission Segment. This week-one navigation message was uplinked to GIOVE-A on 2 May from the Guildford ground station operated by Surrey Satellite Technology Ltd (United Kingdom) and then transmitted from the spacecraft to the users. The objective of the test was to demonstrate an end-to-end link between the Mission Segment and the user receivers. The navigation message is being generated for demonstration purposes only – no service guarantee is provided.
 
The complete radio transmission from GIOVE-A carries a navigation signal and a navigation message. The navigation signal contains the information needed to accurately measure the distance from the satellite to the user receiver. The navigation message provides the timing and spacecraft orbit data needed to calculate the time and exact position of the satellite. One of the main tasks of the GIOVE Mission Segment is the generation of this navigation message.  
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Today, ESA awarded a contract to Surrey Satellite Technology Limited (UK) for initial activities leading to the construction of a second spacecraft for the Galileo satellite navigation system. Named GIOVE-A2, the new satellite (estimated total value 25 to 30 million Euros) will be based on the company’s proven GIOVE-A technology. From now on, there will always be a European navigation satellite in space.
 
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.
 
GIOVE-A2 will help maintain the critical International Telecommunications Union (ITU) frequency filing secured by its predecessor for a further 27 months and facilitate further development of ground equipment.
 
Monitoring of the space environment will also be an important ongoing mission objective for the new satellite. GIOVE-A was the first European satellite to be launched into medium Earth orbit (MEO) and it carries two environmental monitors. These units have been operated almost continuously since launch and are gathering vital data about the Galileo orbit environment that will help in the design of the full constellation.  
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