Joint CSTG/IERS Call for Participation in Satellite and Lunar Laser Ranging

BACKGROUND

Laser ranging to the Moon and artificial satellites was initiated in the 1960s and, during the 1970s and 1980s, matured into an operational space geodetic technique supporting a variety of scientific applications. Satellite laser ranging (SLR) was a significant source of tracking information for early altimeter satellites, such as GEOS-3 and SEASAT, and has provided a long time series of data from the Starlette and LAGEOS satellites since their launch in the mid-1970s.

In the early 1980s, the SLR and Lunar Laser Ranging (LLR) communities participated in MERIT (Monitoring Earth Rotation and Intercomparison of Techniques) to demonstrate the utility of modern space techniques in determining Earth rotation parameters. Earth rotation solutions, based on laser ranging to LAGEOS, have been delivered weekly since 1981, and represent the longest, continuous Earth rotation series obtained using modern space techniques.

In 1987, the newly formed International Earth Rotation Service (IERS) issued a call requesting commitments from the geodetic community to participate in the new IERS program. Since the inception of the IERS on January 1, 1988, SLR, LLR and Very Long Baseline Interferometry have been embraced by the IERS. Since 1988, the laser techniques have not only contributed to the determination of Earth rotation parameters but have become a significant component of the IERS Terrestrial Reference Frame (ITRF) as well, especially in the determination of Earth Center of Mass and scale, and contribute significantly to precision orbit determination for current satellite altimetry (TOPEX/POSEIDON AND ERS-2). Furthermore, SLR data, collected from a variety of satellites, is the dominant contributor to modern gravity field models, such as JGM-3, EGM96 and GRIM4. In addition, LLR has been an important factor in the evaluation of characteristics of Earth-Moon dynamics, including effects associated with general relativity.

PURPOSE

The CSTG Satellite and Lunar Laser Ranging (SLR/LLR) Subcommission Steering Committee and the IERS Directing Board jointly believe it is now appropriate for supporting institutions to reaffirm their future participation in the SLR/LLR effort and to cooperate in a more formal structure designed to improve the operational efficiency of the laser ranging community and to foster data product standardization and new developments. In an era of diminishing resources, an equitable and international distribution of responsibilities meeting the needs of the global scientific community is needed. Toward this goal, the CSTG SLR/LLR Subcommission has developed a "Terms of Reference" document which describes the needs and vision for this new organization, the International Laser Ranging Service (ILRS). The CSTG SLR/LLR Subcommission and IERS Directing Board have agreed to issue this joint "Call for Participation" as a first step in establishing the new ILRS to conduct the operational support and analyses required by the scientific community, including the results contributed to the IERS in support of the International Terrestrial Reference Frame (ITRF).

The supporting operational elements of the new ILRS organization, for which proposals are being sought, are:

Central Bureau - provides overall coordination of global laser ranging activities; maintains documentation and electronic databases; organizes meetings and workshops

Laser Tracking Stations and Subnetworks - acquire and transmit lunar and satellite data to an Operations Center and/or Data Center. Individual stations may submit their proposals separately or as part of a Subnetwork

Operations Centers -provide for the collection and merging of data from the subnetwork, initial data quality checks, data reformatting into a uniform format, compression of data files if requested, maintenance of a local archive of the tracking data, electronic transmission of data to a designated ILRS Data Center; provide sustaining engineering, communications links, and other technical support to a subnetwork.

Regional and Global Data Centers - collect, archive and distribute the data acquired by the stations on behalf of the user community. Global centers archive and provide electronic access to the entire SLR/LLR dataset often in cooperation with Regional or other Global Centers.

Analysis and Associate Analysis Centers - Analysis Centers generate precision ephemerides for the approved satellite constellation and regularly submit Earth rotation results and station coordinates and velocities for ITRF in strict accordance with IERS standards and delivery schedules. Associate Analysis Centers generate products of a specific or specialized nature, provide quality control of the products generated by the various Analysis Centers, and/or generate combination products. Analysis Centers (or Associates) are asked to indicate in their proposal their interest in routinely performing intercomparisons and quality checks of different Center solutions, prior to submission to the IERS, and perhaps even providing "combined solutions" to the IERS.

The duties and functions of the various supporting organizations are described in more detail in the ILRS Terms of Reference which can be accessed via the CSTG SLR/LLR Subcommission Home Page at the following address:

ILRS Terms of Reference

It is highly recommended that all organizations responding to this call review the Terms of Reference document before submitting their proposal.

Policy guidelines for the new ILRS will be set by the ILRS Governing Board, an international elective body which is expected to supplant the current CSTG Satellite and Lunar Laser Ranging Subcommission but retain its CSTG affilliation. The ILRS Governing Board will elect from among its members an Analysis Coordinator who will also serve as the ILRS representative to the IERS Directing Board and, as part of a reciprocal arrangement, the IERS will appoint a representative to the ILRS Governing Board.

CALL FOR PARTICIPATION

The CSTG Satellite and Lunar Laser Ranging Subcommission and the IERS requests proposals for participation in the new International Laser Ranging Service (ILRS). Qualified institutions, or collaborating groups of institutions, are encouraged to submit proposals to serve in one or more of the following areas:

Central Bureau
Laser Ranging Station or Subnetwork
Operations Center
Regional or Global Data Center
Analysis or Associate Analysis Center

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. Further suggestions on proposal format and content for each type of organization will be placed on our CSTG SLR/LLR Subcommission website by January 30, 1998.

PROPOSAL DEADLINE

Detailed proposals must be submitted in writing by March 31, 1998, to:

Dr. John J. Degnan
Chairperson, CSTG Satellite and Lunar Laser Ranging Subcommission
Code 920.3
NASA Goddard Space Flight Center
Greenbelt, MD 20771 USA

The proposals will be jointly reviewed by a special session of the CSTG SLR/LLR Subcommission Steering Committee to be held in advance of the 23rd General Assembly of the European Geophysical Society (EGS) in Nice, France during the week of April 20-24, 1998.and by the IERS Directing Board at its 19 April 1998 meeting. Successful proposers will be notified by early June with a goal of fully implementing the new ILRS organization by November 1, 1998.