DORIS, The Next Generation: A New and Complementary GNSS2 Element

J-Luc. Issler, P. Sengenes, J-P. Berth, B. Belon, L. Lestarquit, P. Ferrage, Ch. Jayles, T. Toumier, M. Brunet, J. Dantepal, D. Bhunstein, J-P. Diris

Abstract:	The French Space Agency CNES (Centre National d’Etudes Spatiales), GRGS (Groupe de Recherches en Geodesie Spatiale), IGN (Institut Geographique National) have designed and developed the DORIS system (Doppler Orbit determination and Radiopositioning Integrated by Satellite) able to determine the position of satellites and ground beacons within a few centimeters. This accuracy is achieved by post processing of very accurate Doppler measurements performed by a spaceborne DORIS receiver. The DORIS signal is transmitted by a worldwide network of ground based beacons, including 50 Orbit determination Beacons (OBs) connected to Ultra Stable Oscillators (USO). DORIS will now integrate a real time on-board orbit determination sofware (DIODE) developed by CNES. This software will fly on SPOT4 and on all the new DORIS receivers. The accuracy achieved with the latest version of this software is better than one meter 3D (1 st.d.). While the present DORIS system is under improvement, CNES performed internal studies concerning a new radionavigation system, taking advantage of DORIS and GPS solutions. This new system is called DORIS Next Generation (DORIS NG). DORIS NG is a patented concept enabling new improvements of the DORIS system (The current DORIS signal has a narrow bandwith, and each beacon transmits at the same frequency. The current DORIS pseudorange accuracy is within a few microseconds). This concept is based on the use of a GNSS like signal: Each beacon transmits a GNSS C/A code, modulating a dual frequency carrier signal, in L and S band. A GNSS like P code could also be added for high robustness and/or high precision applications. DORIS NG can be seen as a worldwide ground network of pseudolites accessible from space. The goal is to use a GNSS signal format, which is now a real international standard and to use GNSS technology and techniques, permanently improved in term of cost and performances, for the receivers and the beacons. Real measurements performed in laboratory with an experimental DORIS NG instrumentation (using low cost commercial GPS receivers and pseudolites connected to USOs) shows the compatibility with the high measurement short term and mid term accuracy required for the current scientific applications. Moreover, the error measurement reduction capability of dual frequency spread spectrum signal could be used to improve the accuracy of the system. The paper describes the system components of DORIS NG, the time synchronisation analysis, the signal performances, the receivers and beacons architecture. Possible synergies between DORIS NG and LAAS systems are described. The tremendous advantage of the use of DORIS NG like systems is to reduce the cost of future GNSS2 projects, such as INES (Inovative Navigation European System) - SCNS (Systeme Complementaire de Navigation par Satellites). Moreover, the scientific and operational interests of multistandard spaceborne receivers, able to process simultaneously navigation satellites (GPS and/or GLONASS) and ground pseudolites (DORIS NG) signals, will be also presented.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	193 - 205
Cite this article:	Issler, J-Luc., Sengenes, P., Berth, J-P., Belon, B., Lestarquit, L., Ferrage, P., Jayles, Ch., Toumier, T., Brunet, M., Dantepal, J., Bhunstein, D., Diris, J-P., "DORIS, The Next Generation: A New and Complementary GNSS2 Element," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 193-205.
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