| Date: | 1999-09-10 00:48:00 | |
| Sender: | Gilles Tavernier/CNES <[Mailed Carey Noll <NOLL@CDDIS.GSFC.NASA.GOV>]> | |
| Subject: | [SLR-Mail] No. 439: Call for Participation in the DORIS Pilot Experiment | |
| Author: | Gilles Tavernier | |
| Content: | ******************************************************************************** SLR Electronic Mail 1999-09-10 00:48:00 UTC Message No. 439 ******************************************************************************** Author: Gilles Tavernier/CNES Subject: Call for Participation in the DORIS Pilot Experiment JOINT CSTG/IERS CALL FOR PARTICIPATION IN THE DORIS PILOT EXPERIMENT DORIS (Doppler Orbitography and Radiolocation Integrated by Satellite) is one of the four techniques contributing to the International Earth Orientation Service (IERS). The three other techniques have an international service providing data and products to the scientific community. There is an increasing demand among the international scientific community for a similar service dedicated to DORIS.=20 The benefit of a possible International DORIS Service (IDS) was discussed during the meeting of the IERS Directing Board held in Postdam in September 1998. The IERS DORIS co-ordinator then transmitted the relevant recommendations to the DORIS Directing Board. On the occasion of the CSTG and IERS Directing Board meetings held in Birmingham in July 1999 in the framework of IUGG99, it was decided to initiate a DORIS Pilot Experiment with a view to establish an International DORIS Service. The IERS expects to recognize the future IDS as the operational entity which is designated to provide DORIS products to IERS.=20 THE DORIS SYSTEM Background The DORIS system was designed and optimized to provide high precision orbit determination and ground station positioning. It was developed to support the TOPEX/POSEIDON oceanographic altimetry mission. It is an up-link radiometric system based upon precise Doppler measurements and using two frequencies, 2 GHz and 400 MHz, well suited to correct for ionospheric effects. In contrast to other navigation systems such as GPS or GLONASS, DORIS is a centralized system. Line-of-sight velocity measurements between the network transmitting stations and the space borne receivers are currently collected and pre-processed by one unique control center located in Toulouse (Mission center).=20 Analyses of the data from DORIS/SPOT2, SPOT3, TOPEX/POSEIDON and now SPOT4, have demonstrated the capabilities of the system for the precise monitoring of station positions and the determination of crustal motions. With high precision determination of the TOPEX/POSEIDON orbit, DORIS contributes also significantly to the success of this altimetric mission. The performance of the system led the IERS to accept DORIS as a fifth geodetic technique to be used in its analysis activities in 1994, i.e. only four years after the beginning of the first mission of DORIS on SPOT2.=20 System evolutions and perspectives Since the first flight on SPOT2 in 1990, several improvements have been implemented on the following instruments. On SPOT4, the orbit is also operationally computed on-board using the DIODE navigator. This software will also be integrated in future DORIS receivers. For ENVISAT, JASON-1 and later satellites, the second generation DORIS instrument will be able to perform simultaneous Doppler measurements from two ground stations, thus reducing the limitations for ground station positioning due to possible interference and increasing the system capacity. On JASON-1 and then SPOT-5, the DORIS instrument will perform a new type of DORIS measurement: an absolute phase measurement. New beacon developments are being performed, such as using the shifted frequency technique that will allow the use of a larger number of stations in the same area. This will greatly increase the number of possible DORIS stations around the world. One can expect significant improvements in orbit determination, ground station localisation, and other application in the next few years. It must also be noted that a significant source of error for DORIS-based positioning might presently come from the insufficient knowledge of the gravity field. Following the CHAMP and GRACE missions, DORIS may improve on its present performance.=20 PURPOSE OF THE DORIS PILOT EXPERIMENT=20 The primary objective of the future IDS, an international collaboration of organizations which operate or support DORIS components, will be to foster the DORIS technique as a joint service to support international geodetic, geophysical, and other research and operational activities.=20 The aim of the DORIS Pilot Experiment is to assess the need and the feasibility of an International DORIS Service. The supporting operational elements of the future IDS organization, for which proposals are being sought, are:=20 o Data Centers -- They archive and distribute the station data and all required information needed by users. They archive and provide electronic access to the products from Analysis Centers.=20 o Analysis Centers -- They perform at least one of the following activities:=20 - generate precise ephemerides for the selected IDS satellites; - submit Earth rotation results; - compute station coordinates and velocities, or position time series as requested by ITRF;=20 - produce special products such as: o ionospheric information, o time varying geocenter coordinates, o static and time-varying coefficients of the Earth´s gravity field; - perform intercomparisons and quality checks of different Analysis Centers solutions;=20 - generate the combined solution of the IDS for submission to the IERS.=20 o Central Bureau -- It provides overall coordination; maintains documentation and electronic databases (e.g., satellite anomalies, site changes, DOMES identification numbers); organizes meetings and workshops.=20 o New temporary or permanent DORIS transmitting stations -- In addition to the current permanent network which will form the primary network used by the IDS, new stations installed temporarily or permanently could be included in the IDS network. Their data would be provided to the Data Centers and would thus be available to the community of users.=20 - A few second-generation beacons should be available in the next few months.=20 - Third-generation beacons are currently being developed. Their shifted frequency capability combined with future dual-frequency receivers flying on board JASON-1 and ENVISAT will increase the system capacity. They will be used to upgrade the permanent network and will also be available for other IDS purposes.=20 o Additional DORIS on-board packages =AD Space Agencies or Research Centers can decide to take DORIS instruments, acquiring data from the station network, on-board satellites and to contribute to IDS.=20 - Data will be available to the other IDS components and to the community of users.=20 - Organizations could develop their own Control Center, or benefit from the support of the CNES DORIS multi-mission ground segment (SSALTO).=20 Policy guidelines for the new IDS will be set by the IDS Directing Board, an international body elected from among the IDS members according to the IDS Terms of Reference.=20 CALL FOR PARTICIPATION Qualified organizations are encouraged to submit proposals for one or more of the following components of the future IDS:=20 o Data Centers o Analysis Centers o Central Bureau o New temporary or permanent DORIS stations o Additional DORIS satellites Before preparing a proposal for a particular IDS component, proposers should carefully read the Terms of Reference which describe the responsibilities and functions of each component. The Terms of Reference can be accessed at the following e-mail address: Gilles.Tavernier@cnes.fr=20 Participants must provide their own financial resources in carrying out their proposed duties. The proposal should clearly address the services and capabilities being offered by the institution (or institutions), its (their) financial ability to carry them out, and appropriate points of contact. Proposal lengths of one to four pages should be adequate for all organization types.=20 PROPOSAL INSTRUCTIONS Letters of intent are expected by 24 September 1999. Organizations must indicate their possible contribution: data, products, and IDS component. Letters or e-mail should be sent to Gilles Tavernier (see Writing Committee - last page). Formal proposals with detailed information about technical, financial and organizational aspects should be submitted in a second step no latter than 1 January 2000 and sent to Gilles Tavernier. Proposals received by the above deadline will be reviewed by the DORIS Pilot Experiment Steering Committee. Proposals received any time after this date will be reviewed by the IDS Directing Board after the IDS is formed.=20 o In consideration of the existing facilities and activities, proposals related to data centers, analysis centers and central bureau can lead to a quick start of IDS activities.=20 o It must be noted that due to the present system constraints (risks of interference), the proposals of stations installation have to be studied and coordinated between all the organizations involved in DORIS stations: permanent network, localization, IDS experiments.=20 o It is, however, important to identify IDS proposals in order to analyze and refine them, define priorities and to be ready to start installation and operation as soon as stations are available. It should be noted that a limited number of second-generation ground beacons might be initially available, and more third-generation beacons later on.=20 o It should also be noted that the back-up receivers from JASON-1 (second generation miniaturized) and ENVISAT (second generation) might constitute boarding opportunities after these satellites launch.=20 PROPOSAL REVIEW Proposals will be reviewed on the basis of their consistency with the future IDS Terms of Reference. Review of the proposals and selection of the IDS components will be made at an DORIS Pilot Experiment Steering Committee meeting held in January 2000. Successful proposers for the IDS components will be notified by February 2000.=20 The DORIS Pilot Experiment Steering Committee members are: Carey Noll, NASA/CDDIS, USA (noll@cddis.gsfc.nasa.gov) John Ries, University of Texas, USA (ries@csr.utexas.edu) Laurent Soudarin, CLS, France (Laurent.Soudarin@cls.fr) Pascal Willis, IGN, France (pascal.willis@ensg.ign.fr) Gilles Tavernier, CNES, France (Gilles.Tavernier@cnes.fr) Do not hesitate to contact one of these persons for any question about the DORIS system (technique, organization, support... ).=20 IDS MILESTONE A ”DORIS DAYS” meeting will be held in Toulouse, France, 2-3 May 2000. This will be the occasion to assess the progress and the future of the DORIS Pilot Experiment, and to exchange information about the DORIS system evolution (JASON-1 and ENVISAT second generation receivers, third-generation ground beacons).=20 Released : September 1, 1999 [Mailed From: Carey Noll ******************************************************************************** |