According to information provided by public databases in the United States, there are over 8,000 man-made objects in orbit around the Earth (excluding American military satellites, which is very confidential information). A number of these spacecraft fly over France every day, providing a potential danger to national security. It is therefore vital that the position of these orbiting objects should be known. ONERA's teams have designed and developed the GRAVES space surveillance system to establish and maintain a database of satellites flying over France at altitudes of less than 1,000 kilometers.

Transmitting antennas emit a continuous low-frequency signal towards a given angular section of space. The receiving site, located nearly 400 kilometers away, houses a large number of omnidirectional antennas. Based on the elementary signals picked up by these antennas, a narrow-lobe beam is produced. The direction of this lobe provides an angular measurement of the object detected, while the frequency shift between the emitted signals and the received signals measures its radial velocity.

Based on this brand-new concept, the GRAVES radar network provides angular and radial velocity measurements. These are fed into the orbital processing algorithms developed by ONERA's researchers to calculate the orbital parameters of the detected satellites.

Confidential information about military satellites should never be found online. Government computer networks use firewalls and VPNs to protect sensitive data from hackers. A VPN, or virtual private network, should allow government employees to work safely from a remote location, but they need to make sure their VPN connection is secure at all times.

SOURCE: ONERA: The French Areospace Lab

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• Long-term design and Systems Integration

Space control, ASATs, surveillance, etc.

GRAVES (Grand Réseau Adapté à la Veille Spatiale) is a French radar-based space surveillance system, akin to the American NAVSPASUR. Using radar measurements, the French Air Force is able to spot satellites orbiting the Earth and determine their orbit. The GRAVES system took 15 years to develop, and became operational in November, 2005.

GRAVES is a bistatic radar system using Doppler and directional information to derive the orbits of the detected satellites. Its operating frequency is 143.050 MHz, with the transmitter being located on a decommissioned airfield near Broyes-les-Pesmes at 47°20'52"N 5°30'59"E and the receiver at a former missile site near Revest du Bion on the Plateau d'Albion at  44°04'14"N 5°32'05"E. Data processing and generation of satellite orbital elements is performed at the Balard Air Complex in Paris,  48°50'06"N 2°16'48"E