Galileo, the European Programme for Global Navigation System is a joint initiative of the EC and ESA. Galileo is the first satellite positioning and navigation system specifically designed for civil purposes. It will offer state of the art services with outstanding performance in accuracy, continuity and availability. It will be more advanced, more efficient and more reliable than the current US GPS system.
Watch an ESA video showing Chilbolton Observatory's role in Galileo (link opens in a new window)
The Galileo system will comprise a global constellation of 30 satellites in Medium Earth Orbit (MEO), three planes inclined at 56 degrees to the equator at about 23,222 km altitude. They are supported by a worldwide network of ground stations.
There are many applications for Galileo:
- Finance, Banking and Insurance
- Agriculture and Fisheries
- Personal Navigation
- Emergency and Crisis Management
- Environmental Management
The Galileo System will be managed and operated in the form of a concession as part of a public-private partnership (PPP).
The Galileo programme is being implemented in three phases:
- The definition phase was completed in 2003 providing the basic specifications for the system
- The deployment and in-orbit validation phase, which is currently underway and aims to perform an in-orbit validation of the system
- The deployment phase which will commence with the launch of the final satellites to complete the constellation
Galileo System Test Bed
Two test satellites, GIOVE A and GIOVE B were launched in December 2005 and April 2008 respectively. The objectives of these satellites were to:
- Make satellite transmission frequency measurements to secure the use of internationally-allocated frequencies
- Validate key technologies such as the rubidium clocks on the satellites
- Test the reception of GPS signals from MEO
- Characterisate the MEO environment using two different radiation monitoring instruments
- Evaluate the use of two parallel transmission channels
Chilbolton Observatory's role
Following the GIOVE A satellite launch and a spacecraft commissioning phase, the satellite navigation payload was activated, and the first signals from the spacecraft were detected on Thursday 12th January 2006 using a purpose-built L-band receiver on the 25 metre Chilbolton antenna. This receiver has been designed and built by RAL engineers, and operates over the frequency band 1100 - 1700 MHz.
In order to meet the frequency filing criteria for the ITU, extensive calibration procedures and tracking tests were made at Chilbolton in the weeks leading up to launch. These procedures made use of signals from existing satellites including Artemis and GPS, together with precise measurements of emissions from the celestial radio source, Cassiopeia A. Chilbolton staff developed a sensitive, flexible and well-calibrated receiving and signal analysis system to allow high quality data to be collected.
Once the satellite was operational measurements were performed during suitable satellite overpasses. Examples of measurements include:
- Equivalent Isotropic Radiated Power (EIRP)
- Power spectrum density
- Carrier-to-noise ratio (C/No)
- Occupied bandwidth
- Out of band emissions
This phase of the project lasted for around 2 months, during which time many overpasses, each lasting ~7 hours, were tracked and recorded by Chilbolton and RAL Space staff.
Since this first measurement campaign, several futher periods of intensive observations of both satellites have been made.
Rutherford Appleton Laboratory's role
Rutherford Appleton Laboratory (RAL) in Oxfordshire is part of STFC (link opens in a new window) along with Chilbolton Observatory. Most of the 200 staff of RAL Space are based at RAL. At RAL the 12 metre antennna of the RAL Ground Station was used to communicate with the GIOVE A satellite, sending commands to control the satellite and receive telemetry data. The RAL Ground Station commenced operations as soon as the satellite was launched.
More information on the Galileo System can be found on the ESA Galileo (link opens in a new window) website.