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First General Meeting of the International Laser Ranging Service (ILRS)

Deggendorf, Germany
Tuesday, September 22, 1998

The transition meeting between the SLR/LLR Subcommission and the new International Laser Ranging Service (ILRS) was held in Deggendorf, Germany on September 22, 1998 in conjunction with the Eleventh International Workshop on Laser Ranging. The list of attendees is included as Attachment 1 (Editor's note: Attachment 1 is the hand written attendance list and is not available online. Please contact mpearlman@cfa.harvard.edu if you wish to get a copy of the attendees). We could tell folks to contact us if they need a list. Although the official date for the start of the ILRS is November 1, 1998, work is already underway to make the transition as smooth as possible.

ILRS Organization

John Degnan gave an overview of the recent activities leading to the establishment of the ILRS (see the ILRS web site at: ILRS History), the selection of participants from the proposals submitted (see Attachment 2), and the election of the Governing Board members (see Attachment 3). It is critical that we get the Working Groups set up as soon as possible. Coordinators and some of the key members of the Working Groups will be selected at the first ILRS Governing Board Meeting on Friday, September 25. Non-board members wishing to volunteer for service on a Working Group should contact John Degnan. Degnan reminded the attendees that the new ILRS web site already contains a great deal of technical and programmatic information and many links to related sites, and we solicit feedback from the general ILRS membership regarding the current and future content of the ILRS Web site. Comments should be sent to Carey Noll or Van Husson.

John Bosworth reviewed the ILRS Charter, ILRS Scientific and Operational Data Products, and the ILRS Components and Organization (see Attachment 4). He then discussed the Role of the Central Bureau, its organization and key personnel, and gave an overview of the major activities underway toward Central Bureau establishment (see Attachment 5). Mike Pearlman gave an item by item status on the setup of the Central Bureau (see Attachment 6). The process of transition has been underway since early in the year. Most of the activity has been focussed on the development of the Central Bureau web site and the rapid production of performance assessment reports for SLR network stations.

Gerhard Beutler, the President of the CSTG, addressed the meeting, pointing out that he was pleased with the progress and plans to date, but that we should not lose sight of the fact that the analysis and the science were areas that needed much attention.

Steve Klosko discussed his role as the new Science Coordinator for the Central Bureau (see Attachments 7, 7a and 7b). The Science Coordinator will work to enhance science dialogue, promote SLR goals and capabilities, promote multi-discipline approaches, and operate proactively to stimulate new and improved science products. Steve sees this as a collaborative effort, with the scientists and analysts all contributing to its success. Major activities here will include the establishment of a web page containing reference lists of SLR-specific publications and publications on related scientific and analysis developments. The need for more user-friendly SLR data products was stressed; routine availability of data products at levels higher than the present normal points would make SLR more useable to the non-specialist. In particular, if observation equations could be generated during the network operations and QC procedures, they could be made available with little or no additional effort.

ILRS Web Site

Van Husson gave a demonstration of the ILRS web site, its layout, features and some of the planned division of responsibilities (see Attachment 8). The web site, which has been developed and managed by Van Husson and Carey Noll, with help from Mark Torrence, is located at http://ilrs.gsfc.nasa.gov.

IGEX 98 Campaign

Werner Gurtner reviewed the preparations for the IGEX 98 Campaign (see Attachment 9). IGEX 98, which is the first global GLONASS campaign and the first real test of the combined GLONASS/GPS receivers, will start on October 19 and run for three months. A web site for the activity has been established at:

http://Lareg.ensg.ign.fr/IGEX

Werner discussed some of the hardware and data considerations and the request for SLR support. SLR can provide an evaluation of the microwave-determined orbit. Nine GLONASS satellites have been chosen as targets, three in each orbital plane. Since some SLR stations have scheduling constraints, the Governing Board will set some hierarchy of priority within these nine satellites (see notes from the ILRS Governing Board meeting on October 25). It may even make sense to define strategies to share the tracking among stations which are in close proximity. The request for SLR support includes 1 to 2 five minute normal points at the start, middle, and end of each pass tracked.

Satellite Predictions

During the past two years the SLR community has implemented very successful procedures for daily updates of satellite orbital (prediction) elements with Time Bias Functions (TBF). IRV providers generate the updates, RGO is the clearinghouse, and EDC distributes the files.

To improve predictions further, in particular for some of the more difficult satellites where TBF ‘s degrade rapidly over a day or where maneuvers make predictions obsolete, RGO has been generating sub-daily IRV’s for distribution to the stations.

Roger Wood reported that RGO plans to generate sub-daily IRV’s for the satellites in the GLONASS Campaign using positional data derived by AIUB from broadcast elements.

In the long run, Roger recommends provision of daily or sub-daily elements for all SLR satellites to be used with automated processing at all of the stations, thereby eliminating the need for the TBF. Roger sees this as an opportunity to replace the present force and reference models with one that takes better account of drag and solar radiation pressure. Eventually, we might expect real-time corrections at the stations using the tracking data. This proposal will be turned over to the Data Formats and Procedures Working Group for a recommendation.

Satellite Status

We agreed to discontinue SLR tracking on RESURS1/3 and METEOR-2/Fizeau. The retroreflector experiments can continue with tracking of the new WESTPAC satellite. Since the last meeting of the SLR/LLR Subcommission, approval has been granted for SLR tracking of GFO-1 and WESTPAC, and for the special three-month campaign on GEOS-3 that is scheduled to begin in October.

Next Meeting

The strategy for scheduling ILRS General Meetings was discussed. There was general consensus that we should continue to meet twice a year (at workshops, WEGENER Meetings, EGS or AGU Symposia, etc.) as we did under the SLR/LLR Subcommission. Best options for the next general meeting are the EGS meeting at the Hague in April or the AGU meeting in Boston in May. The IUGG/WEGENER meeting in July was viewed as too late.