The consecutive realizations of International Terrestrial Reference Systems (ITRS; McCarthy and Petit, 2004) are computed using data from Satellite Laser Ranging (SLR), Doppler Orbitography
and Radio-positioning Integrated by Satellites (DORIS), Very Long Baseline Interferometry (VLBI) and GPS.
This system uses a radar operating in the VHF band and allows obtaining orbitography
information on satellites in low orbit.
France has recently embarked on a permanent space surveillance capability in a newly-opened facility near Lyons; manned 24/7 by air force crews, it will deploy the Systeme d'Information Spatiale, a space situational awareness C2 granted to a consortium led by Thales Alenia Space end-2014; the SIS will leverage expert tracking of space weather, as well as the modernised Graves bistatic radar mapping objects in low orbit, designating some to dedicated orbitography
radars or optical telescopes.
and Radio-positioning Integrated by Satellite (DORIS) on board enables precise determination of the orbit.
It will include two (or three) installations that will compute orbitography
, check the integrity of signals, develop radio navigation messages and monitor the services.
DORIS (Doppler Orbitography
by Radiopositioning Integrated on Satellite) technology determines orbits of host satellites (Spot2, Spot3, Spot4, TOPEX/Poseidon and Spot5 in the future), station coordinates and EOP from dual-frequency Doppler observations; the transmitter--see Fig.
DORIS DORIS (Doppler Orbitography
and Radiopositioning Integrated by Satellite).
2012) used Singular Spectrum Analysis and the Wavelet Transform, to assess noise levels in DORIS (Doppler Orbitography
and Radiopositioning Integrated by Satellite) time series, to better determine the nonlinear station motion.
This also includes orbitography
services and precise location of these missions.
Another way to measure distances to satellites is with DORIS (Doppler Orbitography
and Radiopositioning Integrated by Satellite), which was built and is operated by the French space agency, known as CNES.
Data from the Global Positioning System (GPS) was introduced in 1991 and from Doppler Orbitography
and Radio-positioning Integrated by Satellite (DORIS) in 1994.
The POD using DORIS (Doppler Orbitography
and Radiopositionning Integrated by Satellite) data, realized in the framework of the IDS (International DORIS Service) (Willis et al.