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Grand Réseau Adapté à la Veille Spatiale
(Large Network Adapted to the Space Watch)

Since 2005, France has had a limited loworbit space surveillance capability using the GRAVES system (Grand Réseau Adapté à la Veille Spatiale). Commissioned in 2005, the radar system GRAVES (Grand network adapts to the space surveillance), which tracks space debris and observation satellites and listening foreign evolving at an altitude between 400 and 1,000 km, is operated by the military operations center monitoring space debris (COSMOS), based on the air base 942 Lyon Mont-Verdun.

Graves is based in France, with a transmission site located in eastern France and reception site, southeast, on the Plateau d'Albion. Both sites are distant 400 km, which limits vis-à-vis detection capability of very little inclined orbits on the equator but still limited. With this unique radar in Europe, the Air Force detects and tracks space objects moving from 400 to 1000 km above the earth. It allows especially to know the trajectory of foreign observation satellites or listening and anticipating the threat of space debris for French satellites.

The Military Surveillance Operational Centre of Space Objects ( COSMOS - Centre Opérationnel de Surveillance Militaire des Objets Spatiaux ) is located on the Air Base 942 in Lyon Mont-Verdun deals with space surveillance and the transmission of state information on national security. It depends on the Air Force from which tasks are assigned via the Command of Air Defense and Air Operations (CDAOA - Commandement de la Défense Aérienne et des Opérations Aériennes). Currently, the staff assigned to COSMOS is a twenty soldiers of the Air Force.

Many of the spacecraft flying daily over France constitute a potential threat to the home defense. Therefore it is essential to always know the position of these objects. In this context, the Spaceguard GRAVES system, designed and developed by ONERA teams represents an extremely promising tool of the future, able to maintain an updated database of objects flying over France, at a lower altitude 1 000 km.

There are 9,000 satellites or objects larger than ten centimeters orbiting the Earth in US catalog responsible for identify. However, it is likely that objects in orbit high can be cataloged if their size exceeds ten centimeters. These satellites 9000 or objects, many of them fly over France daily, threatening potential for homeland defense. Americans have to date a real system operational space before.

Designed and developed by ONERA in the 1990s, the GRAVES system consists of a bistatic radar (transmission site near Dijon and the reception site on the Albion plateau in the Alpes-de-HauteProvence) and an operating server used by the COSMOS Lyon Mont-Verdun. Developed by ONERA under contract to the DGA, it uses a specific signal processing technology developed in the laboratories of ONERA. GRAVES, operated by airmen of the military operations center monitoring space debris, contributes to the space component of the Air Defense assigned to the Air Force.

Using an entirely new concept, it provides angular and radial velocity measurements from which orbitography treatments developed by ONERA researchers can calculate the orbital parameters of the satellites detected. 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.

On the transmitting site, antennas transmit a continuous signal to low frequency in a given angular sector in space. Distant nearly 400 km, the reception site houses a large number of antennas, omnidirectional. From elementary signals received by them, a narrow lobe beam is produced. The direction of this lobe will provide an angular measurement of the detected object, as the frequency offset between the transmitted and received signals provides a measurement of the radial velocity.

Designed to look up to 1000 kilometers, the radar can follow more than a quarter of the satellites in orbit, and the majority of those considered most threatening. For maximum effectiveness of the detection system, two main constraints were defined. On the one hand, a maximum detection time of 24 hours was fixed, which means that all satellite should be seen with a recurrence of 24 hours. On the other hand, the collected measures must ensure a capacity of orbit determination on the first pass.

Hence the solution proposed by Onera, based on bistatic radar scanning. On the transmitter site, antennas emit a signal continuous low frequency in a given angular sector in space. Further south, the reception site home to a number of omnidirectional antennas. It's from the received elementary signals by them that is reconstituted by calculating a narrow lobe beam, . The direction of this lobe will provide an angular measurement of the detected object, while the offset frequency between the transmitted and received signals provides a measurement of the radial velocity.

This system, unique in Europe, should be an operation of "keeping performance to the 2025-2030 horizon," according to what was planned military planning law (LPM) 2014-2019 . Hence the notification, announced that on 12 December 2016, by the Directorate General of Armaments (DGA) a contract to this effect at the national studies and Aerospace Research Agency (ONERA) and society Degreane Horizon. The amount of the order was not specified.

Thus, ONERA will be responsible for the "renovation and receiving sites improvements and operating and maintenance will guarantee the performance of the system and their extension" while the transmission site's responsibility.

In order to be compatible with existing catalogs, including the US catalog, the catalog of French orbital elements is the "two lines" format. The data released by Graves will only affect a fraction of what the US system may be observed. With a single sensor is capable Graves to observe nearly a quarter of all the objects listed by the US catalog. GRAVES has probably a processing consistency much higher than what the Americans have.

During the first campaign, Graves helped identify some satellites do not appear in the catalog of orbital elements distributed by the Americans. In addition, the US voluntarily limit the production of the data at 24 hours whereas the frequency of cooling elements provided by Graves is 12 hours in 70% of cases. "It is all interest to have its own space surveillance system and to ensure well against a any cessation of the distribution of these data, "notes Jacques Bouchard, a research engineer in the department "Prospective and synthesis" (DPRS). The culmination of a project after thirteen years of work, in the course of the summer will be conducted a second test campaign to test the system orbitographic Graves. Once again, Jacques Bouchard and his wife Aline will team up to use the measurements collected by the radar, piloted from Onera. Then the system orbitographic will be delivered to military and connected to the radar via the Air Force network. It then remained to perform some finer settings of the system, including software, in 2006.

In December 2015 was held the first service test campaign final system whose development required thirteen years of work. For eleven days. Jacques Bouchard, orbitography designer and software developer of this system, checked the capacity these tools to establish a database of orbital elements from the processing steps angular and radial velocity collected by the radar. A second campaign, lasting more long, should be carried out before this orbitographic system is delivered to the air force.

"Solar activity has an influence in particular on the ionospheric refraction and hence the quality measurements. Therefore, it may be that the system knows some fluctuations, "says engineer Châtillon. That said, the data provided by the space surveillance system will available for use in fall 2005. Jacques Bouchard, will be the culmination of a Working thirteen, thirteen years, much of which he made during Development software "high dose", taking a particular job. "It's pretty rare to see the result such a project, "he said.

The modernization of the GRAVES system had been minimal. As explained in May 2015 by General Jean-Daniel, the joint ommandant of space, these "renovations will not allow to continue to detect military objects whose size is reduced constantly, like nanosatellites and CubeSat, or follow a growing number of objects unless improve the performance of the radar."

The Directorate General of Armaments (DGA) awarded on 10 November 2016 a contract for the renovation of the radar system GRAVES (Grand network adapts to space situational awareness) at the National Studies and Aerospace Research Agency (ONERA), co-contracting with the company Degreane Horizon. The GRAVES renovation will help treat the natural obsolescence of a system which entered service in 2005 and, ultimately, improve detection performance against space objects increasingly numerous and increasingly smaller dimensions.