CSTG Satellite and Lunar Laser Ranging Subcommission

1998 Annual report

John J. Degnan

Code 920.3, Geoscience Technology Office

NASA Goddard Space Flight Center

Greenbelt, MD 20771 USA

1. INTRODUCTION
2. RECENT SUBCOMMISSION MEETINGS
3. INTERNATIONAL LASER RANGING SERVICE (ILRS)
4. 11^th INTERNATIONAL WORKSHOP ON LASER RANGING
5. NEW AND UPCOMING MISSIONS AND CAMPAIGNS
6. CONCLUDING REMARKS
7. REFERENCES

1. INTRODUCTION

The past year was an extremely active one for the satellite and lunar laser ranging community. Much of the activity was centered on the creation of the new International Laser Ranging Service (ILRS) which is scheduled to begin full operations on 1 November 1998. As in past years, the number of laser-tracked satellites continued to grow, new stations are being established, SLR technology continues to improve, and new applications are being developed.

2. RECENT SUBCOMMISSION MEETINGS

Since the last annual report [1], the SLR/LLR Subcommission General Assembly has met at the following locations:

In addition, the Subcommission Steering Committee met on the following occasions:

Full reports for all of these meetings have been posted on the CSTG SLR/LLR Subcommission Web Site at the following URL:

CSTG SLR/LLR Report

The new ILRS Governing Board met for the first time on 25 September 1998 in Deggendorf, Germany, and supplanted the CSTG SLR/LLR Subcommission as the international governing body.

top of document

3. INTERNATIONAL LASER RANGING SERVICE (ILRS)

3.1 Recent Events Leading to the Establishment of the ILRS

As projected in last year’s report [1], the draft ILRS Terms of Reference were presented and approved on 13 June 1997 at the Subcommission General Assembly in Maratea, Italy. Comments were taken from the community and incorporated where appropriate in the draft. The ILRS Terms of Reference and Working Group Charters were also posted on the Subcommission Web Site.

In the last quarter of 1997, Dr. John Degnan, the CSTG SLR/LLR Subcommission Chairman, and Dr. Bob Schutz, SLR Representative to the IERS Directing Board, drafted a Joint CSTG/IERS Call for Participation in the new service. Following a final review by the SLR/LLR Subcommission Steering Committee, the CSTG President, and the IERS Directing Board, the Call was distributed on 24 January 1998 via SLRmail, IGSmail, and SGGmail with proposals due by 31 March 1998. The Call requested proposals for a new ILRS Central Bureau and the various operational components which make up the ILRS, i.e., Tracking Stations and Subnetworks, Operations Centers, Analysis and Associate Analysis Centers, as well as Global and Regional Data Centers. The proposals were evaluated at a special meeting of the CSTG SLR/LLR Subcommission Steering Committee on 18 April 1998 held in conjunction with the European Geophysical Society (EGS) Symposia in Nice, France. The Steering Committee findings were presented the following day to both the CSTG Executive Board, chaired by Prof. Gerhard Beutler, and to the IERS Directing Board, chaired by Dr. Christoph Reigber. Both boards approved the Subcommission’s deliberations. The IERS Directing Board appointed Dr. Bob Schutz as the voting IERS Representative on the new ILRS Governing Board. The approved responses to the Joint Call were then presented at the CSTG SLR/LLR Subcommission General Assembly on 21 April 1998.

The response by the SLR community to the Joint Call was outstanding and resulted in the approval of 46 ILRS tracking stations, 4 ILRS Operations Centers, 3 ILRS Analysis Centers, 4 Lunar Analysis Centers, 18 Associate Analysis Centers, 2 Global Data Centers and 1 Regional Data Center. The current list of approved ILRS organizations is summarized in Table 1. The Central Bureau was established at the NASA Goddard Space Flight Center with John Bosworth as Director and Michael Pearlman of the Harvard-Smithsonian Center for Astrophysics (CfA) as Secretary. In accordance with the ILRS Terms of Reference, Mr. Bosworth and Dr. Pearlman, along with Prof. Beutler, will serve as ex-officio members of the ILRS Governing Board.

top of document

TABLE 1: APPROVED ILRS ORGANIZATIONS

ILRS Central Bureau

NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA
Director: John Bosworth
Secretary: Michael Pearlman

ILRS GLOBAL DATA CENTERS

Germany
Eurolas Data Center (EDC)
DGFI, Muenchen

USA
Crustal Dynamics Data Information System (CDDIS)
NASA GSFC, Greenbelt, MD

ILRS REGIONAL DATA CENTERS

China
Shanghai Data Center, Shanghai

ILRS OPERATIONS CENTERS

Russia
Russian Mission Control Center, Moscow

USA
NASA Satellite Laser Ranging (NSLR), Greenbelt, Maryland
UT Operations Center for LLR, Austin, Texas

top of document

ILRS ANALYSIS CENTERS

ILRS LUNAR ANALYSIS CENTERS

ILRS ASSOCIATE ANALYSIS CENTERS

top of document

ILRS STATIONS/SUBNETWORKS

top of document

3.2 Network Representatives on the ILRS Governing Board

Following the Nice General Assembly, the three major SLR networks (i.e., NASA, EUROLAS, and WPLTN) were each requested to appoint or elect two members to serve on the Governing Board prior to solicitation of nominations for elected members. This activity was completed in July 1998 with the appointment of David Carter and John Degnan of the United States as the NASA representatives, Werner Gurtner of Switzerland and Wolfgang Schleuter of Germany as the EUROLAS representatives, and Hiroo Kunimori of Japan and Yang Fumin of China as the WPLTN representatives.

3.3 ILRS E-mail Directory

During period April to July 1998, each of the ILRS centers was requested to provide complete and up-to-date email lists to Ms. Carey Noll for the purpose of setting up peer group exploder lists to be used by the Central Bureau in conducting Governing Board elections and facilitating communications within the ILRS. Letters were also sent out by the CSTG SLR/LLR Chairperson to the Primary Technical Contact to every organization that responded to the Joint Call informing them of their ILRS status. All ILRS Associates have been encouraged to confirm that they are properly included in the ILRS E-mail Directory which can be found at the following URL:

ILRS Email Information

If information is missing or incorrect, please contact Ms. Carey Noll at noll@cddisa.gsfc.nasa.gov.

3.4 ILRS Governing Board Elections

Nomination and election of all but the final two At-Large members of the Governing Board took place in July and August via email within the appropriate peer groups. Peter Shelus of the United States was chosen as the Lunar Representative, Wolfgang Seemueller of Germany as the Data Center Representative, and Richard Eanes of the United States and Ron Noomen of The Netherlands as Analysis Center Representatives. Following completion of this first round of GB elections, the call for nominations of the two At-Large members went out in September via email to all ILRS Associates of record. John Luck of Australia and Francois Barlier of France were chosen from a list of nine At-Large candidates to complete the Governing Board membership.

3.5 First ILRS General Assembly

The final CSTG SLR/LLR Subcommission General Assembly and first ILRS General Assembly was held on the evening of 22 September 1998 in conjunction with the 11^th International Workshop on Laser Ranging in Deggendorf, Germany. Subcommission Chairman, John Degnan, reviewed the ILRS activities since the previous General Assembly in April and announced the outcome of the ILRS GB elections. John Bosworth and Michael Pearlman gave overviews of recent activities initiated within the new Central Bureau. Steven Klosko of Raytheon STX discussed his initial plans as the new Science Coordinator within the Central Bureau, and Van Husson of AlliedSignal Technical Services Corporation (ATSC) provided an online tour of the current ILRS Web Site and a discussion of its future expansion. The ILRS Web Site, which already contains much useful information and links to related sites, can be accessed at the following URL:

ILRS Home Page

top of document

The ILRS Central Bureau solicits feedback from the ILRS Associates regarding the current and future informational content of the web site. Please contact Van Husson (HussonV@thorin.atsc.allied.com) and Carey Noll (noll@cddisa.gsfc.nasa.gov) with your comments and suggestions.

Following some additional business, John Degnan officially disbanded the CSTG Satellite and Laser Ranging Subcommission and replaced it with the new International Laser Ranging Service. Power to make policy was simultaneously transferred from the CSTG Subcommission Steering Committee to the newly elected ILRS Governing Board. Like the earlier Subcommission, the ILRS will retain its subordinate affiliation to the CSTG Executive Board as stated in the ILRS Terms of Reference. An organizational diagram of the ILRS is provided in Figure 1.

Figure 1: ILRS Organization

top of document

A more complete summary of this and future ILRS General Assemblies will be routinely posted on the ILRS Web Site.

3.6 First ILRS Governing Board Meeting

The new ILRS Governing Board held its first meeting on 25 September 1998 immediately following the SLR Workshop. In accordance with the Terms of Reference, the GB elected from among its membership a Chairperson as well as Coordinators and Deputy Coordinators for each of the four standing Working Groups (WG’s). The Governing Board elected John Degnan as ILRS GB Chairperson, Hiroo Kunimori as Missions Coordinator, Ron Noomen as Analysis Coordinator, Werner Gurtner as Networks and Engineering Coordinator, and John Luck as the Data Formats and Procedures Coordinator. In addition, each GB member was asked to volunteer to serve on a WG. Table 2 provides the current distribution of GB members among the various Working Groups.

The Coordinators were then tasked by the Chairman to invite other ILRS Associates to serve on their respective Working Groups and to submit their membership lists to the Central Bureau by 1 November 1998. Several candidates for WG membership were recommended by GB members at the meeting based on their unique contributions and talents in the areas of SLR engineering, analysis, and/or operations. All ILRS Associates are encouraged to serve on one of the Working Groups if asked.

A more complete summary of this and future ILRS Governing Board Meetings will be routinely posted on the ILRS Web Site.

top of document

4. 11^th INTERNATIONAL WORKSHOP ON LASER RANGING

The 11^th International Workshop on Laser Ranging was held during the week of September 21-25 in Deggendorf, Germany. The sponsoring agency, Bundesamt fuer Kartographic und Geodaesie (BKG), and the Program Committee, chaired by Dr. Peter Sperber, assembled a highly successful technical, scientific, and social program. This was the first year the Workshop was approved as an IAG-sponsored Symposium. This designation also allows students to apply for financial aid from the IAG.

The Workshop attracted a record number of attendees (over 150), and, in spite of continuing fiscal pressures worldwide, the mood of the attendees was optimistic and upbeat and several new and interesting science applications and technical ideas were put forward. For example, Dr. Vladimir Vassiliev and coworkers described a new concept for a solid glass geodetic satellite without cube corners which is modeled after the "Luneberg Lens" concept previously used in microwave systems.

Progress on several automated or remotely operated SLR systems (e.g., NASA’s SLR2000 system, the Japanese Keystone system, Australia’s new Mt. Stromlo site, and Switzerland’s upgraded Zimmerwald station) was described and a few of the new systems are rapidly approaching an operational status. Global distribution of the SLR network was improved by the transfer of the NASA MOBLAS-8 system from Quincy, California, to the island of Tahiti in French Polynesia. The new site is jointly sponsored by NASA, CNES, and the French University of the Pacific. China has completed a new transportable station and is planning to build a second. Workshop participants were also shown the new two-color TIGO SLR station which uses a frequency-doubled Titanium-Sapphire laser operating near 800 and 400 nm. The state-of-the art Matera Laser Ranging Observatory (MLRO) has demonstrated both high precision (mm precision normal points) and near 100% data yield off LAGEOS 1 and 2 and has successfully ranged to the Moon from a site in Greenbelt, MD not far above sea level. MLRO is now being upgraded to two colors for atmospheric refraction correction prior to shipment to Italy.

Departing slightly from past Workshops, the technical and scientific program included several invited speakers representing the scientific community as well as competing space geodetic techniques such as VLBI, GPS, DORIS, and PRARE. Time varying gravity was a major theme in the scientific talks. The usefulness of SLR in calibrating other microwave navigation and radar surveillance systems was a common technical theme.

Scientific interest in the use of the SLR network to support global time transfer and the intercomparison of newly developed atomic clocks (e.g., the ultrastable Cesium Fountain and Cryogenic Sapphire clocks) at the 50 picosecond level was high as evidenced in papers by Robert Vessot of the USA and Ettiene Semaine of France.

top of document

Dr. Kenneth Nordtvedt emphasized the scientific importance of gathering lunar range data in the technically difficult periods near "full" and "new" moon. Dr. Nordtvedt also endorsed the use of interplanetary laser transponders, of the type recently proposed by NASA Goddard, for improved tests of general relativity and for monitoring relative motions between the Solar System and Celestial Reference Frame. In response to the new lunar ranging requirements, an impromptu technical meeting was held to discuss the possibility of submitting a proposal to the Japanese Space Agency for a simple "echo" laser transponder on the Selene II lunar mission, scheduled to be launched in 2003. Dr. Uli Schreiber of Germany agreed to lead the proposal effort with technical support from NASA and the LLR community. Such a transponder would make the Moon accessible to most SLR stations in the global network.

The Italian Space Agency has volunteered to host the 12^th Workshop in Matera, Italy in approximately two years time.

5. NEW AND UPCOMING MISSIONS AND CAMPAIGNS

5.1 Recently Launched Satellites

On 10 February 1998, the U.S. Navy launched the GFO-1 (GEOSAT Follow-on) Oceanographic Mission from Vandenberg AFB in California. SLR tracking support began on 22 April 1998. SLR once again proved its value as an "insurance backup" when four redundant GPS receivers on the newly launched U.S. Navy all failed to achieve stable tracking. Current high precision orbits are being provided by SLR alone. Orbital parameters for GFO-1 are:

top of document

On 10 July 1998, the Western Pacific Laser Tracking Network (WPLTN) launched its new WESTPAC geodetic satellite from Russia. SLR tracking commenced on 15 July 1998, There was some initial confusion following launch which was caused by NORAD assigning the wrong COSPAR ID for this satellite. The Israeli Satellite TechSAT was erroneously tracked instead of WESTPAC. The SLR community has agreed the correct COSPAR ID for WESTPAC is 9804301 (for more information see SLRMail 146). The WESTPAC satellite is covered with recessed retroreflectors of the Russian Fizeau design to permit only one retroreflector to contribute to the return. On average, 0.7 corner cubes contribute to the return, and therefore the return signal fades in and out as different reflectors come into view. The satellite is well-suited to advanced two color ranging experiments.

WESTPAC Orbital Parameters

5.2 Special Campaigns

In addition to the new satellites, several older satellites, combined with modern centimeter accuracy systems, have proven to be a valuable source of new gravity field data. At the request of Richard Biancale of CNES, the global SLR network collected several months of new data on the Diadem-C and Diadem-D satellites during the past year. A similar gravity-related campaign on the old GEOS-3 satellite, suggested by Frank Lemoine of NASA, is scheduled to begin on 15 October 1998. The GEOS-3 campaign will last a minimum of three months with a possible extension to six months.

SLR tracking of ERS-1 resumed on 20 July 1998. The European Space Agency (ESA) decided to reactivate some instruments of the retired ERS-1 satellite in order to complete a final Tandem Phase with ERS-2 dedicated to Synthetic Aperture Radar (SAR) experiments. The duration of the tandem operations is expected to be several months but will be dependent on the health of the seven year old ERS-1 satellite.

5.3 Upcoming Missions

Figure 2 gives a timeline on satellites which have been tracked since 1985 or will be tracked in the foreseeable future. At the first ILRS General assembly, it was announced that tracking will cease on the METEOR-Fizeau and RESURS-3 missions. The engineering tests on the Russian Fizeau effect retroreflector designs have been completed, and the new WESTPAC geodetic satellite uses this design.

Table 3 provides a list of upcoming space missions which have requested or are expected to request SLR tracking along with their sponsors, intended application, and projected launch dates. More complete information on these satellites can be found by visiting the ILRS Web Site URL provided previously in this document.

top of document

Table 3: Future SLR Missions

top of document

6. CONCLUDING REMARKS

In the past year or two, we have seen the departure of several individuals who have made significant and longlasting contributions to SLR, and I wish to take this opportunity to publicly acknowledge their efforts.

Dr. Andrew Sinclair has recently announced his retirement from the Royal Greenwich Observatory in the UK. Besides being an outstanding analyst and making major contributions to the establishment and operations of the Herstmonceax SLR station, Andrew served as the first president of EUROLAS and as an active CSTG SLR/LLR Steering Committee Member where he headed the Data Formats and Procedures Working Group for many years.

During the recent SLR Workshop, Dr. Ing. Herman Seeger, who obtained the funding for the German Wettzell SLR Station and the Totally Integrated Geophysical Observatory (TIGO), retired from his post as President of Bundesamt fuer Kartographic und Geodaesie (BKG) in Germany, formerly known as the Institut IfAG. Herman has also been an avid supporter of technology development for Very Long Baseline Interferometry (VLBI).

Dr. Christian Veillet has decided to pursue his astronomical interests on the island of Hawaii. Under Christian’s outstanding technical leadership, the French CERGA station in Grasse became the world’s premier lunar laser ranging facility and the first intercontinental time transfer at the 100 picosecond level was demonstrated using the LASSO instrument on the METEOSAT-P2 satellite.

On behalf of the satellite and lunar laser ranging community, I wish to thank these outstanding individuals for a job well done and extend to them best wishes for the future.

7. REFERENCES

1. Degnan, John J., "1997 CSTG Satellite and Lunar Laser Ranging – Subcommission Report", CSTG Bulletin #13, Section II - Advanced Space Technology, Eds. G. Beutler, H. Drewes, and H. Hornik, Munich, 1997

top of document

Responsible Government Official: Carey Noll
NASA's Privacy Policy and Important Notices

Send us your comments

Last modified date: Friday, November 05, 2004
Author: Carey Noll
Maintained by: Carey Noll