French space surveillance system update

[The translation looks a little approximate in places; I'll try to find
the original.]

http://www.emb-fr.int.ar/tec/imgs/FranceST_075_US.pdf

FranceST # 75 - 08/24/2005

Special Report


Graves (Large Network Adapted to Space Surveillance) is a space
surveillance system created and developed by Onera teams for the
General Weapons Delegation (DGA). Last December the first trial run of
the final operating system took place, the development of the system
took thirteen years.

Jacques Bouchard, research engineer with Onera's DPRS (Long-Term Design
and Systems Integration) department, and creator and developer of the
orbitographic software for the system, verified the ability of these
tools to establish a database of orbital elements by processing angular
measurements and radial velocity data collected by radar. A second,
longer trial will be completed before the orbitographic system is
delivered to the army in the autumn.

9,000 satellites or objects whose size is larger than ten centimeters
orbit around the Earth - according to the American database which
records them. However, it is possible that objects in higher orbit
cannot be cataloged, even if their size exceeds ten centimeters. Among
these 9,000 satellites or objects, many pass over France daily,
creating a potential threat to national security.

American currently has an operational space surveillance system
composed of two very distant receptors (the distance that separates
them is longer than the length of the American continent). This device
creates a sort of large, vertical curtain. As soon as a satellite
crosses the curtain, it is chased by a pursuit radar. There is also a
Russian space surveillance system on which little information is
available. In this context, Onera has been suggesting since the
beginning of the 1990's the creation of a radar called Graves, which
would allow the surveillance of satellites that could observe French
territory.

More than a quarter of satellites followed by Graves Consisting of two
autonomous subsystems, a radar that takes measurements and
orbitographic algorithms that transform them into a database of orbital
elements, the proposed system has made several compromises. Graves is
based in metropolitan France, with an emission site situated in eastern
France and another in the southeast, on the Albion Plateau. The two
sites are 400 kilometers apart, which limits the ability of detection
vis-=88-vis orbits subtly inclined to the equator, but they are few.
Created for observations up to altitudes of 1,000 kilometers, this
radar can follow more than a quarter of satellites, the majority of
those considered the most threatening.

To obtain maximum efficiency from the detection system, two principal
constraints have been defined. One, a maximum detection delay of 24
hours was set, which signifies that each satellite should be seen with
a recurrence of 24 hours. Also, the measurements collected must be able
to determine the orbit from the first passage. Hence the solution,
suggested by Onera, using a bistatic scanning radar.

On the emission site, antennae emit a continuous, low-frequency signal
toward a given, angular sector of space. To the south, the reception
site houses a large number of omnidirectional antennae.

"Based on signals received from these antennae, a narrow lobe beam is
produced," explains Jacques Bouchard. "The direction of the lobe
provides an angular measurement of the object detected, while the
frequency shift between the signals emitted and received measures its
radial velocity."

Guarantee the independence of the country's space surveillance

Since 1992, Jacques Bouchard has been working full time on the
development of Graves as a spatial mechanics specialist. He began by
defining the project, determining the zone that should be scrutinized
by the radar to ensure the mission objectives - to provide users (the
military) a database of orbital elements updated daily. Next, he
created simulation software for the instrument to verify that it was
capable of meeting the objectives.

Finally, Jacques Bouchard expanded the software to use the
orbitographic measurements, work that just ended with the orbitographic
system test campaign last December. This trial was mainly carried out
with his wife, Aline Bouchard, also a DPRS research engineer, who
ensured the software tests. "We had to verify that we were able to
establish a database of orbital elements by processing the data
provided by the radar." The objective of this campaign was also to
verify the quantity and the quality of data produced by the radar,
which underwent huge modifications since the was prototype tested in
2001 (double emission power, new signal processing algorithms that are
six times more powerful).

In order to be compatible with existing databases, particularly the
American one, the French orbital elements database is in the "two
lines" distribution format. "The data distributed by Graves will only
concern a fraction of what the American system can observe. The
American catalog lists objects whose height is near the Moon, a
distance of about 300,000 km," notes Jacques Bouchard, who clarifies
that the American system is much richer in measurement sensors. That
said, with one sensor, Graves is capable of observing nearly a quarter
of the total number of objects listed in the American catalog. "We
undoubtedly have a data processing coherence highly superior to the
Americans'," he thinks.

During the first campaign, Graves enabled the listing of some
satellites that don't appear in the American database of orbital
elements... Furthermore, the Americans voluntarily limit the production
of their data to 24 hours, while the frequency of renewal of elements
provided by Graves is 12 hours in 70% of the cases. "It is imperative
to have our own space surveillance system and have a guarantee against
a possible blackout in data distribution," states Jacques Bouchard.

The completion of a project after thirteen years of work

Sometime this summer a second test campaign will be carried out. Its
goal is to test the Graves orbitographic system. Once again, Jacques
Bouchard and his wife Aline will team up to use the measurements
collected by radar, piloted from Onera. Next, the orbitographic system
will be delivered to the military and connected to radar via the air
force's network. Then some fine tuning will be done, mostly on the
software, during 2006. "Solar activity has an influence, particularly
on ionospheric refraction, thus on measurement quality. Consequently,
the system could experience some fluctuations," declares the engineer
from Ch=89tillon.

That said, the data provided by the space surveillance system will be
available and usable beginning autumn 2005. For Jacques Bouchard, this
will be the end of thirteen years work, a good many of which he spent
creating the "high dose" software, a time-consuming effort. "It is
fairly rare to see the end of this type of project," he acknowledges.

Contacts :

Onera - Dominique Huard - tel : +33 (0)1 46 73 40 65 - email :

[The translation looks a little approximate in places; I'll try to find
the original.]

http://www.emb-fr.int.ar/tec/imgs/FranceST_075_US.pdf

The original is at
http://www.emb-fr.int.ar/tec/imgs/FranceST_075_FR.pdf.

I'll leave out the text, as the various accented characters don't seem
to be coming through too well. If anyone here knows how to fix that,
I'd like to know.