NASA will be performing network maintenance on Wednesday, November 20, 2024, between 11:00 AM EST and 1:00 PM EST (16:00 to 18:00 UTC). There will be two periods of about five minutes of disruption. During these peroids, the ILRS website will be unavailable during the outages. If you experience problems outside this window, contact support-cddis@nasa.gov.

close window

Second General Assembly of the International Laser Ranging Service (ILRS)

The Hague, Netherlands
Thursday, April 22, 1999

Editor's Note: All Attachments are available in hard-copy. Please contact Dr. Michael Pearlman (email Pearlman@cfa.harvard.edu), ILRS Central Bureau Secretary,  if you would like a copy of an attachment.

The Second General Meeting of the International Laser Ranging Service (ILRS) was held at the Hague, Netherlands, on 22 April 1999, in conjunction with the European Geophysical Society Symposium. The list of attendees and the meeting agenda are included as Attachments 1 and 2.

The Governing Board (GB) Chair, John Degnan, welcomed the participants and gave a brief overview of the first GB meeting in Deggendorf, Germany, in September 1998 and subsequent GB activities (see Attachment 3). The formation of the Working Groups, the further review and development of their charters, and the formulation of their tasks and priorities has been a major step in the organization of the ILRS. Several new tracking campaigns have been organized to support user needs.

It is likely that the International Association of Geodesy (IAG), the parent organization of the CSTG, will be reorganized at the IUGG meeting in Birmingham. Bob Schutz announced at the GB meeting that the IERS is also being reorganized. It has been suggested by Gerhard Beutler, President of CSTG, that the ILRS, IGS, and IVS (and possibly other radio technique services) be given equal Technique Center Status within the IAG. The precise level within the IAG is not yet clear, but the centers will have representation on both the CSTG and IERS Executive Boards. It has been proposed that each Center will have two representatives to the IERS, one each from networks and analysis. Each of the Technique Centers will have its own data archive and be responsible for organizing product submission to the IERS. These will be discussed in Boston during AGU in early June. The IERS wants single products from each technique; it will be the responsibility of the technique to do the integration into a single product. The reorganization will be discussed at the AGU Meeting in Boston in early June and finalized in Birmingham.

Central Bureau

The Central Bureau has been active over the last six months. Van Husson reviewed the status and performance of the network (see Attachment 4). Over the last year, eight new stations have begun operations. Mt. Stromlo (replacing Orroral) has had an impressive performance since last May. The new station in Kunming, the new LLR station in Grasse, the four Keystone systems, and TIGO started contributing data this past year. Nearly half the stations met or came close to the 1000 pass standard for LEO satellites. Fifteen of the stations (about 40%) met or approached the 400 pass standard for LAGEOS. About half the network provided at least minimum performance on the high satellites, driven mainly by the IGEX 98 Campaign. Several stations on the ILRS roles have been inactive and it was noted that we do not have an on-line report on network station status. The FTLRS is being upgraded to support the JASON mission. Plans are afoot by EOS to upgrade the Riyadh station with components from the now closed Orroral Station. Several stations were noted as being non-compliant with data delivery, normal point bin size, and/or configuration files. It also appears that some stations are starting their LAGEOS normal point intervals at other than the even minute as specified in the normal point definition. Four new SLR stations are imminent in (1) Argentina (TLRS-4), (2) South Africa (MOBLAS-6), (3) Kiev, and (4) MLRO (Matera)

Mike Pearlman reviewed other areas of progress by the Central Bureau (see Attachment 5). Dialogue has been underway with the SUNSAT Mission; the Mission Support Request Form was completed and submitted to the Missions Working Group for its recommendation. The Central Bureau has continued the development of the ILRS web site. Mirrored sites are now available at CRL and EDC. The Science Pages have been expanded to include bibliographies and Earth science links. Historical satellites, collocation histories, updated SLR brochure material, and mail exploders have been added. The brochure provides some new charts for SLR presentations; everyone is invited to use them. Campaign weekly reports are being routinely issued. The first version of the SLR bibliography, organized by year and author, is on line for review and augmentation. Members are urged to access the site and add additional material. It is intended to have all SLR related material properly referenced for access. A hard copy library of early documentation has been assembled and is listed in the on-line bibliography. It was agreed that we are not getting proper review and concurrence on all of the web contents, and that the GB and CB should proceed with its plan for formalizing "ownership" of all of the ILRS web pages. A first outline of the ILRS Annual Report was presented for members to begin thinking about their contribution. The first report should be issued in early 2000 and will therefore be a major topic at the Fall 99 ILRS meeting in Florence , Italy. Our plan is to issue the full report on the "electronic press" with a summary in hard copy. All ILRS functions are expected to contribute. The Central Bureau has met with most of the working groups. A list of Central Bureau action items on the web site and databases are included in Attachment 5. A number of additional Central Bureau action items will result from the working group reports to follow later in the meeting.

The ILRS banner and stationary were presented for approval (see Attachment 5). It was agreed that the first letter in each word should be green (the same color as the flash) instead of blue in order to further highlight "ILRS".

Peter Dunn reported that "Fence data", a radar product from the US Navy, has been made available to NASA on a number of LEO satellites, including GFZ-1, to test its utility for SLR predictions (see Attachment 6). The Fence data will soon be incorporated by GFZ into the GFZ-1 acquisition process, and all stations are urged to make a special effort to track. GFZ-1 is now at an altitude of about 300 km and losing altitude quickly, with reentry estimated by early June. It was suggested that perhaps the past Fence data and doppler data could also be used for the GFZ-1 orbit analysis during this reentry process. One minute orbit data are now being posted daily at: http://magus.stx.com/GFZ.

Issues that need attention from the Central Bureau include:

  • Develop on-line weekly reports on station status;
  • Follow-up on station compliance issues; and
  • Implement a structure for web page "ownership" to ensure proper concurrence prior to placing material on the ILRS web site.

Working Groups

Task lists presented by each of the Working Groups (below) often involve other Working Groups and the Central Bureau. At the end of this report we have separated these tasks by each entity.

Missions (M/WG)

Scott Wetzel presented the report for the M/WG (see Attachment 7). Its charter has been drafted and its membership recruited. The Mission Support Request Form has been developed and is now awaiting installation on the ILRS web site in interactive form. The form has been completed by the SUNSAT mission and it is now with the M/WG for review and recommendation. The form has also been sent to the IRS-P5 (India) and VCL (NASA) missions to be completed for submission. After submission of the form and approval by the Governing Board, the next step is the development of a tracking support plan. It was agreed that new missions should submit a preliminary form early so that the M/WG and the Governing Board can provide early feedback and suggestions. A final version of the form can be submitted closer to launch. It was suggested that proposers of new campaigns using satellites already in orbit should also have to submit a Missions Support Request Form or some variant of it. Several of the working groups pointed out the need for standardization and documentation of the center-of-mass corrections. This will be the responsibility of a newly organized ad hoc working group (see below), but the center-of mass definition for each satellite is the responsibility of the M/WG. There are still some unresolved issues on the GLONASS numbering system, but it isn’t clear if this adversely affects SLR tracking.

The M/WG identified the following items that they need to address:

  • Define the submission requirements for new campaigns using satellites already in orbit;
  • Formulate a procedure for the development of tracking support plans and specify the contents required;
  • Develop a system to keep track of user requirements and to reaffirm the need to keep satellites on the tracking priority list; and
  • Resolve the GLONASS numbering system to the extent that it is necessary for SLR tracking identification

It was also pointed out that fuel use changes the center-of-mass over the lifetime of satellites. It was agreed that the Missions Working Group should determine this significance and, if necessary, develop a means of quantifying and keeping track of it.

Data Formats and Procedures (DFP/WG)

John Luck presented the report for the DFP/WG (see Attachment 8). The Working Group membership and its charter were ratified in January 1999. A meeting of the Working Group and friends was held on Tuesday, April 20. The members developed a list of tasks and issues to be addressed within the ILRS. The following three special study groups or teams were proposed:

Improve Prediction (Prediction Study Group within DFP/WG)

The present experience with GFZ-1 shows a clear shortcoming of our current prediction system. The DFP/WG has organized a Prediction Study Group to investigate ways of updating predictions more rapidly (sub-daily if necessary) using expedited data product flow, rapid inter-station updates, and new options for orbital element formats. The Prediction Study Group will include: Roger Wood (Convener), Rolf Koenig, Wolfgang Seemueller, Brion Conklin, Werner Gurtner, and Jan McGarry (if she is available). The first report with recommendations is due at the ILRS Meeting in Florence in September, but a plan of attack should be developed over the next 90 days.

Minimum Data per Normal Point (Normal Point Study Group within DFP/WG)

Some of the groups that process SLR data have the feeling that normal points with few raw data points add little to the information content, suffer a significant rate of rejection, and add labor to the analysis process. The DFP/WG has organized a Normal Point Study Group to determine the minimum number of raw data for viable normal points. They would do this by examining the frequency of rejection as a function of raw data count per normal point to determine if there is a pattern that would help define a reasonable minimum raw data requirement for different satellite classes. The Normal Point Study Group members include: John Luck (convener), Richard Eanes (LAGEOS I &II), Graham Appleby (ETALON I & II), Gerd Gendt (ERS I & II), Peter Dunn (Starlette and Stella), Vladimir Glotov (WESTPAC), Tim Springer (GLONASS and GPS). Reports on each satellite are due on June 14 to John Luck with recommendations.

Center-of-Mass and Signal Processing (Signal Processing Ad Hoc Working Group - Recommended)

In spite of our past efforts, center-of-mass corrections for the retroreflector satellites for the various system configurations and concurrent signal processing have not been standardized or documented in accessible form. It was recommended that an Ad Hoc ILRS Working Group be formed to: determine the accurate corrections for the major observing configurations, determine the optimum processing strategies, and propose procedures for documenting and applying the corrections. Candidate members for the Signal Processing Working Group include: Graham Appleby (convenor), John Luck, Andrew Sinclair, Reinhart Neubert, Ulrich Schreiber, Georg Kirchner, Toshi Otsubo, Tom Zagwodzki, Mike Selden, Stefan Riepl, Leigh Dahl, and Peter Dunn. The first step in the working group activity would be to provide a broad characterization of the geodetic (spherical) satellites at the ILRS Meeting in Florence in September. GPS was also identified as a high priority candidate.

The DFP/WG recommended the following:

1. The ILRS should adopt the format used for ERS by D-PAF for notification of satellite maneuvers; DFP/WG will prepare a statement of the required format for the CB to post on the ILRS web site and for the Missions WG to advise satellite operators;

2. DFP/WG should provide the format of drag function coefficients and the algorithm for their implementation to the CB for posting on the ILRS web site;

3. The ILRS should adopt official ILRS names for formats and products:

   ILRS NP for Normal Point formats and data (formerly "CSTG ONP")
   ILRS FR for Full-Rate formats and data (formerly "MERIT-II Full-Rate");

   The CB should note these definitions on the ILRS web site;

4. The Data and Operations Centers should document file naming conventions, recipient addresses (E-mail, FTP), delivery schedules, and transmitted file structures (e.g. all passes/day in one file, sequence constraints) currently in satisfactory use by the stations and the CB should post them on the ILRS web site;

5. The CB should document IRV provider names, their acronyms (e.g. as used in the time bias functions), and the satellites they support, and post them on the ILRS web site;

6. The Missions Working Group should clarify satellite identification by:

  • documenting standard names, acronyms and designators for all retroreflector satellites and provide them to the CB for posting on the ILRS web site; and
  • recommending a standard system of designators for satellites in data and file-naming (it was noted that our 7-digit COSPAR ID is unknown to COSPAR);

7. The contents of certain fields (epoch time scale indicator, wavelength, and calibration and configuration indicators) in the ILRS FR files should be made consistent with ILRS NP conventions; the CB should post these changes in the format definition on the web site;

Byte 44, the Epoch Time Scale Indicator, add UTC(GPS) is to be code 4

Bytes 65-68, Wavelength,  Same as ILRS NP bytes 21-24

Bytes 126-128, Calibration & Configuration Indicators, Amend to agree with ILRS NP bytes 45-47

8. The CB should institute a web site report on weekly system status with non-producing stations being designated as "status unknown" unless the status for such stations is reported;

9. The DFP/WG should develop standardized software packages for use by the ILRS entities by;

  • documenting the algorithms used in data preprocessing; and
  • organizing an activity to write standardized software routines in the most-used languages for the most-used platforms, for all new algorithms;

10. The DFP/WG should propose a method of standardization for assigning Site Occupancy Designators (which are changed for occupancy by mobile systems, or when major upgrades occur), that will be consistent with the DOMES Designators and CSTG GGSS requirements;

11. The CB should implement an on-line site information directory, starting with forms developed by the Networks and Engineering Working Group to be completed by the stations, and including a means to ensure reliably and timeliness of the information; and

12. The CB should make Y2K information and experience available by posting:

  • the results of the Y2K tests conducted by NASA/ATSC for many elements within the NASA Network;
  • information offered by UNAVCO (Barbara Perin) on PC Y2K issues;
  • Other relevant Y2K information provided by ILRS affiliates based on their experience or references that they have found; and

The DFP/WG Coordinator exhorts all participants to test ALL their systems and to beware of complacency.

Networks and Engineering (NE/WG)

Werner Gurtner presented the report for the NE/WG (see Attachment 9). The working group has drafted its charter and has confirmation of participation from most of its candidate members. The Working Group Activity Plan included the following:

1. Develop qualifying procedures for new SLR systems to join the ILRS;

2. Develop a catalog of satellite specific tracking properties including link budgets for use in tracking operations;

3. Develop a consistency and format check program for ILRS normal point files to be run on-site (may be consolidated with #9 under DFP/WG);

4. Develop a catalog of quality checks performed by the Analysis Center with specification of feedback required by the tracking sites;

5. Develop a flow chart for the SLR data from the stations to the Data Centers (may be consolidated with #4 under the DFP/WG);

6. Develop a site/system description form to be used in development of site catalog (may be consolidated with # 11 under DFP/WG);

7. Define the requirements for time tagging SLR data;

8. Develop a flow chart of the SLR predictions incorporating all stations and sources (may be consolidated with #5 under DFP/WG);

9. Document system calibration procedures; and

10. Develop procedures for prioritizing special passes and preventing the tracking of others during specified periods.

Several of these items will involve other working groups and the Central Bureau. The NE/WG will prioritize these items and distribute responsibility among its membership to begin addressing them.

Analysis (A/WG)

Ron Noomen presented the report for the A/WG (see Attachment 10). The Working Group has drafted its charter (see ILRS web site) and has confirmed participation of its members. More will be invited to join. Lunar data is now submitted in ILRS Normal Point Format from both Texas and Grasse. The University of Texas is also undertaking the conversion of the back data. The biggest issue for the A/WG is to work toward integrated ILRS data products for the IERS.

The Working Group has identified the following items that it needs to address:

1. Complete the adoption of SINEX format for all ILRS data products;

2. Examine options for providing ILRS data results as time series products;

3. Organize a program to compare solutions (results) from the Analysis and Associate Analysis Centers and to document the differences; and

4. Develop an integrated data product for ILRS submission to IERS.

The Working Group plans to organize a workshop prior to the next ILRS meeting in Florence to develop a plan of action.

Campaigns

Diademe Campaign

Richard Biancale reported on the Diademe (D1C and D1D) SLR tracking campaign which took place April – November 1997 (see Attachment 11). Twenty-six stations provided about 5000 passes between the two satellites. The campaign was considered successful with a few caveats. Tracking was weak in the Southern Hemisphere due to the combination of few stations and magnetic stabilization of the satellite. There was some difficulty interpreting the normal points (at the few cm level) due to the number and distribution of the retroreflectors. Some success at precise ranging (separating the signals from the separate arrays) was achieved with the full-rate data and the SPAD detectors (first photon detection).

The data has been used to improve the GRIM5 gravity field. SLR residuals for the D1C and D1D satellites are reduced considerably with the improved field.

IGEX 98

Werner Gurtner reported on the IGEX 98 Campaign that ran from mid-October, 1998 through mid-April 1999 (see Attachment 12). The SLR Network provided 6650 pass segments on the nine original GLONASS satellites (one of them failed during the campaign) and the three new GLONASS satellites launched during the campaign. Several analysis groups are now comparing the radio and SLR results. Some preliminary result presented by Tim Springer showed a few cm offset between the radio and SLR data, a number comparable to the radio-SLR offset observed on GPS. Graham Appleby presented some results that showed a 1/rev oscillation, suggesting a reference frame issue. Discontinuities in the residuals also need some scrutiny. Since Graz and RGO are the only groups presently presenting radio-SLR results, it was suggested that both should be included as analysis centers within IGEX 98. Further examination of the data will focus on such things as center-of-mass correction and phase center of the radio antenna. A workshop in IGEX 98 is scheduled for September 13-14 in Nashville, Tennessee (USA). Orbital comparisons will be one of the topics of discussion.

An informal request for continued SLR tracking was made by IGEX 98. They were requested to structure a more formal (more specific) request based on inputs from its analysis centers and its plan to continue operating GLONASS receivers in the field. It was agreed to continue the IGEX 98 SLR campaign for an additional two weeks (through May 10) while such a request could be formulated.

GEOS-3

Peter Dunn, standing in for Frank Lemoine, reported on the GEOS-3 Campaign that ran from mid-October 1998 through mid-April 1999 (see Attachment 13). The campaign was considered successful. Over the six month duration, it provided 2225 passes from 31 network stations. The data is being used for refinement of the gravity field. Frank is processing the data and plans to present the results (and its impact) at the IUGG meeting in Birmingham in July. Stay tuned.

GFO-1

Peter Dunn, again standing in for Frank Lemoine, reported on the GFO-1 Campaign which began in earnest when it was realized that the GPS receivers aboard the satellite were not functioning (see Attachment 14). The satellite has a history of spontaneously stowing itself in safe mode. The owner of the satellite, the US Navy, is trying to preempt this erratic behavior by inducing safe mode maneuvers at scheduled times. The spontaneous and programmed maneuver processes has disturbed predictions for the SLR network, complicating the tracking effort, but better communications between the mission operators and the NASA SLR Operations Center have been established in recent weeks. Some altimeter data has been taken and will be available through NOAA, but it too is erratic and the owner’s interest appears to be waning. Additional interest from NASA included the modeling of the macro-model for the non-conservative forces. So far, SLR has provided a full year of data, which is deemed sufficient for this modeling activity. Frank is asking only for a maintenance level of tracking support from this point on, just to examine some of the long period influences. Could this be done with Fence data? At the moment, it is not clear that there is any strong advocate for continued SLR tracking on GFO-1. We need to resolve if the U.S. Navy, NASA, or anyone else needs continued SLR tracking? If so, then proper justification and proper warning of maneuvers must be provided to the network.

ERS-1

Mike Pearlman, standing in for Heiner Massmann, reported on the ERS-1 campaign that started in July 1998 and is scheduled to continue through December, 1999 (see Attachment 15). ERS-1 is now eight years old, far surpassing its original design lifetime. However, since the PRARE tracking system on ERS-1 failed, SLR is the only onboard tracking system. The tracking campaign has been successful, averaging about 10 passes per day. The only shortcomings have been the weakness of coverage in the Southern Hemisphere and the relatively weak data flow over the weekends. The tracking data are being used by: universities, space agencies, and research centers to support the InSAR analysis for the study of Earth motions and deformations. The data are also being used to refine gravity field models. The altimeter on ERS-1 is no longer being operated due to spacecraft power limitations.

GFZ-1

Mike Pearlman, again standing in for Heiner Massmann, reported on the GFZ-1 campaign that started right after launch in April 1995 and will end at its reentry, now estimated to be early June (see Attachment 16). The campaign provided adequate data until the satellite altitude dropped below about 350 km last year. Very few passes have been tracked over the past six months. Fence data is now being incorporated in the predictions to try to help with acquisition. The data has been used to improve harmonics in the gravity field model (GRIM4-S4G) and for intensive studies of surface force models. The GFZ-1 experience was also viewed as a precursor for other low orbiting missions such as CHAMP and GRACE. At this point the value to gravity field modeling is considered marginal at best, but the tracking priority will be maintained as a test of the value of the Fence data.

WESTPAC

John Luck reported on the WESTPAC Campaign that started in July 1998, shortly after launch. Thirty stations have provided a little over 1000 passes over the last nine months (see Attachment 17). This is about a factor of 2-3 times smaller that Starlette. The return rate depends strongly on the angle between the satellite spin axis and the line-of-site, and returns come in bursts, as a consequence of the baffling around the cubes. Preliminary results indicate that the single-shot precision is slightly better than Stella. The MCC is now being funded by WPLTN to support acquisition and analysis of performance.

WPLTN requests that the high priority tracking status be continued and that full-rate data with signal strength information be provided where possible.

SUNSAT

Erricos Pavlis reported on the status of SUNSAT (see Attachment 18). The Missions Tracking Requirement Form is awaiting a recommendation from the Mission Working Group. In the interim, NASA has generated predictions and has attempted ranging with no success. There is some speculation that there may be a problem with the orientation of the spacecraft. The tracking campaign will not start until the performance of the retroreflectors is verified. The GPS seems to be working, but the constraints on its operating schedule, due to limitations in power, have not yet been determined. The retroreflectors are blocked above 80 degrees, but that imposes no serious limitation.

Review of Satellite Priorities

The current list of satellite and lunar tracking priorities are included in Attachment 19. SUNSAT is indicated where it would be included according to the standard formula for priority allocation. We agreed to the following actions:

  1. GEOS-3 will be removed;
  2. GFZ-1 will remain until reentry;
  3. If the need for GFO-1 tracking cannot be supported it will be removed;
  4. IGEX 98 priorities remain until May 10; the revised proposal from IGEX 98 will be reviewed by the Governing Board and a decision on GLONASS priorities will then be made; and
  5. In the longer term, M/WG will implement a survey to reaffirm tracking requirements on all satellites on the list.

Closing Announcements

The next General Meeting and Governing Board Meeting of the ILRS will take place during the week of September 20, 1999 in conjunction with the Colloquium on SLR Calibration Issues and the Conference on Laser Ranging and Atmospheric LIDAR in Florence, Italy. Time has already been allocated for the ILRS on Wednesday, September 22. Information on the Colloquium is included in Attachment 20. For more details contact Ulli Schreiber. Note also that there is an IAU Colloquium on Polar Motion the following week in Cagliari.

The International GLONASS Experiment (IGEX-98) will hold a Workshop in Nashville, Tennessee on September 13-14, just prior to the GPS-99 Conference. Time has been allocated for presentation of the SLR results and for comparison of the radio and SLR measurements. For more details contact Werner Gurtner.

Misc. Material

Some update information on the Helwan SLR system, provided by Tony Novotny, is included in Attachment 21.

Proposals made to the Governing Board for immediate action:

1. Adopt the ERS/D-PAF format for notification of satellite maneuvers;

2. Adopt the following official names for ILRS formats and products:

      ILRS NP for Normal Point formats and data (formerly "CSTG ONP")
      ILRS FR for Full-Rate formats and data (formerly "MERIT-II Full-Rate");

3. Change the current description of the ILRS FR format to make the contents of certain fields in the ILRS FR files consistent with ILRS NP conventions:

Data prepared with the new conventions must contain ‘3’ in Byte 129 (Format Revision Number Indicator). (This makes an implementation date less critical.)

    Byte 44, Epoch Time Scale Ind, UTC(GPS) is to be code 4
    Bytes 65-68, Wavelength, Same definition as ILRS NP bytes 21-24
    Bytes 126-128, Calibration & Configuration Indicators, Amend to agree with ILRS NP bytes 45-47

4. Charter the Signal Processing Ad Hoc Working Group as structured by the DFP/WG.

ACTION PLANS

Central Bureau:

1. Institute a web site report on weekly system status with non-producing stations being designated as "status unknown" unless the status for such stations is reported;

2. Follow-up on station compliance issues;

3. Implement a structure for web page "ownership" to ensure proper concurrence prior to placing material on the ILRS web site;

4. Document (through the Operations and Data Centers) file naming conventions, recipient addresses (E-mail, FTP), delivery schedules, and transmitted file structures (e.g. all passes/day in one file, sequence constraints) currently in satisfactory use by the stations and post them on the ILRS web site;

5. Document IRV provider names, their acronyms (e.g. as used in the time bias functions), and the satellites they support, and post them on the ILRS web site;

6. Document changes to the description of the ILRS FR format to be consistent with ILRS NP conventions;

7. Implement an on-line site information directory, starting with forms developed by the Networks and Engineering Working Group to be completed by the stations, and including a means to ensure reliably and timeliness of the information;

8. Make Y2K information and experience available by posting on the web site:

  1. the results of the Y2K tests conducted by ATSC/NASA for many elements within the NASA Network;
  2. information offered by UNAVCO (Barbara Perin) on PC Y2K issues; and
  3. ILRS member provided Y2K relevant information from either their experience or references that they have found; and

9. Update the satellite tracking priority list by;

  • Deleting Geos-3;
  • Following up as necessary with GFO-1; and
  • Following up as necessary with IGEX-98.

Missions (M/WG)

1. Define the submission requirements for new campaigns using satellites already in orbit;

2. Formulate a procedure for the development of tracking support plans and specify the contents required;

3. Develop a system to keep track of user requirements and to reaffirm the need to keep satellites on the tracking priority list;

4. Resolve the GLONASS numbering system to the extent that it is necessary for SLR tracking identification;

5. Clarify satellite identification by:

  • documenting standard names, acronyms and designators for all retroreflector satellites and provide them to the CB for posting on the ILRS web site; and
  • recommending a standard system of designators for satellites in data and file-naming (it was noted that our 7-digit COSPAR ID is unknown to COSPAR); and

6. Determine the significance of center-of-mass changes over the lifetime of satellites with expendables aboard and, if necessary, develop a means of quantifying and keeping track of it.

Data Formats and Procedures (DFP/WG)

1. Organize a Prediction Study Group to investigate ways of updating predictions more rapidly (sub-daily if necessary) using expedited data product flow, rapid inter-station updates, and new options for orbital element formats, with the first report including recommendations due at the ILRS Meeting in Florence in September;

2. Organize a Normal Point Study Group to determine the minimum number of raw data for viable normal points, by examining the frequency of rejection as a function of raw data count per normal point to determine if there is a pattern that would help define a reasonable minimum raw data requirement for different satellites classes;

3. Prepare a statement of the ERS/D-PAF type format for satellite maneuvers for the CB to post on the ILRS web site and for the Missions WG to advise satellite operators;

4. Provide the format of drag function coefficients and the algorithm for their implementation to the CB for posting on the ILRS web site;

5. Develop standardized software packages for use by the ILRS entities by;

  • documenting the algorithms used in data preprocessing; and
  • organizing an activity to write standardized software routines in the most-used languages for the most-used platforms, for all new algorithms; and

6. Propose a method of standardization for assigning Site Occupancy Designators (which are changed for occupancy by mobile systems, or when major upgrades occur), that will be consistent with the DOMES Designators and CSTG GGSS requirements.

Networks and Engineering (NE/WG)

1. Develop qualifying procedures for new SLR systems to join the ILRS;

2. Develop a catalog of satellite specific tracking properties including link budgets for use in tracking operations;

3. Develop a consistency and format check program for ILRS normal point files to be run on-site (may be consolidated with #5 under DFP/WG);

4. Develop a flow chart for the SLR data from the stations to the data centers (may be consolidated with #4 under the CB);

5. Develop a site/system description form to be used in development of site catalog;

6. Define requirements for timing tagging SLR data;

7. Develop a flow chart of the SLR predictions incorporating all stations and sources (may be consolidated with #5 under CB);

8. Document system calibration procedures; and

9. Develop procedures for prioritizing special passes and preventing the tracking of others during specified periods.

Analysis (A/WG)

1. Complete the adoption of SINEX format for all ILRS data products;

2. Examine options for providing ILRS data results as time series products;

3. Organize a program to compare solutions (results) from the Analysis and Associate Analysis Centers and to document the differences;

4. Develop an integrated data product for ILRS submission to IERS, and

5. Develop a catalog of quality checks performed by the Analysis Center with specification of feedback required by the tracking sites;

The Working Group plans to organized a workshop prior to the next ILRS meeting in Florence to develop a plan of action.

Signal Processing Ad Hoc Working Group (New):

1. Determine accurate center-of-mass corrections for the major observing configurations and the optimum processing strategies;

2. Recommend procedures for applying and documenting these corrections; and

3. Provide a report on the broad characterization of the geodetic (spherical) satellites at the ILRS Meeting in Florence in September.