DORIS and the International DORIS Service: Current status and Planned Evolution

DORIS is one of the four techniques that contributes to the International Terrestrial Reference Frame (ITRF). The technique was developed to support orbit determination on LEO satellites, most notably the suite of ocean radar altimeter satellites. As far as ITRF products (positioning and Earth orientation parameters), there are two points of inflection where there were notable improvements in DORIS system performance. The first occurred in 2002, with the launch of Envisat and SPOT-5 which carried dual-channel DORIS receivers and simultaneously allowing DORIS to became a five satellite constellation. The second point of inflection occurred in 2008 with the launch of Jason-2, which was the first of a series of satellites to carry the seven-channel DGXX receiver, significantly increasing the quantity of DORIS data available. In parallel to the evolution in the DORIS satellite receivers, since the 1990's a long-term effort has been undertaken to improve the quality and stability of the ground monumentation.

Presently a major upgrade of the DORIS network is being carried out that will help DORIS meet GGOS requirements of stability and accuracy for the Terrestrial Reference Frame. Next-generation antennas (Starec Type "C"), where the 2 GHz phase center location is defined to a precision of +/- 1mm, have already been deployed to about 12 sites. This deployment will continue into the future as beacons undergo maintenance.

In the coming decade, DORIS Receivers will be embarked on the Jason-CS, SWOT, Sentinel-3C,3D, and HY-generation of satellites, ensuring that the DORIS constellation consists of a minimum of five satellites.

A further evolution of the IDS is the exploitation of RINEX data by the DORIS analysis centers. The RINEX data provides phase and pseudorange observables. All the new satellites only provide this type of data, which is available much more quickly than the V2 Doppler data available for earlier missions. The RINEX data will allow analysis centers to process DORIS data closer to real time than is the case at present.

This paper will present an overview of the evolution of the DORIS system as characterized by its ground network, satellite constellation, and will discuss how changes in analysis strategy will affect the delivery of DORIS products in the next decade.