[IGSMAIL-2481] Call for Participation in the DORIS Pilot Experiment

[Gilles]

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IGS Electronic Mail      Thu Sep  9 10:26:37 PDT 1999      Message Number 2481
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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. 

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. 

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). 

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. 

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. 

PURPOSE OF THE DORIS PILOT EXPERIMENT 

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. 

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: 

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. 
o Analysis Centers -- They perform at least one of the following
  activities: 
  - 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; 
  - 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; 
  - generate the combined solution of the IDS for submission to the
    IERS. 
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. 
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. 
  - A few second-generation beacons should be available in the next few
    months. 
  - 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. 
o Additional DORIS on-board packages ­ 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. 
  - Data will be available to the other IDS components and to the
    community of users. 
  - Organizations could develop their own Control Center, or benefit from
    the support of the CNES DORIS multi-mission ground segment (SSALTO). 

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. 

CALL FOR PARTICIPATION

Qualified organizations are encouraged to submit proposals for one or
more of the following components of the future IDS: 
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 at cnes.fr 

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. 

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. 
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. 
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. 
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. 
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. 

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. 

The DORIS Pilot Experiment Steering Committee members are:

   Carey Noll, NASA/CDDIS, USA (noll at cddis.gsfc.nasa.gov)
   John Ries, University of Texas, USA (ries at csr.utexas.edu)
   Laurent Soudarin, CLS, France (Laurent.Soudarin at cls.fr)
   Pascal Willis, IGN, France (pascal.willis at ensg.ign.fr)
   Gilles Tavernier, CNES, France (Gilles.Tavernier at cnes.fr)

Do not hesitate to contact one of these persons for any question about
the DORIS system (technique, organization, support... ). 

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). 

Released : September 1, 1999


[Mailed From: Carey Noll <NOLL at CDDIS.GSFC.NASA.GOV>]