Gilles Tavernier

Current status of the doris pilot experiment and the future international doris service

Abstract The aim of the DORIS Pilot Experiment is to assess the need and feasibility of an International DORIS Service. A Call for Proposals was broadcasted in September 1999 to prompt qualified organizations to submit proposals for components of the future IDS. DORIS Days were held in Toulouse (May 2–3, 2000). This second version of these Doris days was in particular devoted to a review of the start-up of the Doris Pilot Experiment. This paper recalls the objectives of the future IDS, points out its components and structure, and gives information on the current and future activities.

The current evolutions of the DORIS system

Abstract DORIS was developed for precise orbit determination and precise positioning on Earth. Three new satellites fitted out with dual-channel second-generation receivers have been recently launched. Jason-1, ENVISAT and SPOT-5 acquired a real autonomy thanks to DIODE real time on-board orbit determination software. Today the DORIS system has built up a global network of 55 stations. In order to reach new accuracy goals for Jason-1 and ENVISAT, it was decided to improve the long-term stability of the antennas when necessary. Third-generation beacons deployed from the end of 2001 offer new features and greater reliability. The satellites relay acquired and stored data at regular intervals to SSALTO, the new DORIS mission control center. DORIS data from the different satellites are currently available in the two Data Centers and used by the International DORIS Service Analysis groups.

DORIS-DIODE: two-years results of the first European Navigator

Abstract The DORIS system was developed to support high accuracy orbit determination and beacon positioning. For the first time, thanks to DIODE, the SPOT-4 satellite orbit is determined in real time on-board with an accuracy of 3–5 meters. Two year DIODE/SPOT-4 monitoring shows that this Navigator has been operational 99.4 % of the time with a few meters accuracy, even through maneuvers. An improved version of DIODE will be loaded on board SPOT-4 next year and will fly, including new upgrades, on board Jason-1, ENVISAT and SPOT-5. Simulations performed using TOPEX/POSEIDON DORIS measurements show that a sub-meter accuracy will be reached with Jason-1.

The proposed International DORIS Service

In 1999, an International DORIS Experiment was initiated under the aegis of the International Association of Geodesy. Since then, 3 new DORIS satellites have been launched carrying improved Doppler receivers. In addition, the DORIS tracking network has also been steadily improved. In 2001, a DORIS analysis campaign was launched. Several groups participated using different software and providing weekly and monthly time series of results, making them available on Internet. The goal of this paper is to discuss the status of the DORIS Pilot experiment, to analyze the progress made during the past 2 years and to propose the official creation within the IAG of an International DORIS Service (IDS). Such a service would operate in conjunction with the already existing IGS, IVS and ILRS as part of the proposed International Global Geodetic Observing System (IGGOS).