ILRS Governing Board Meeting

Nice, France
Wednesday, April 24, 2002


Graham Appleby, David Carter, John Degnan, Hermann Drewes, Werner Gurtner, Carey Noll, Ron Noomen, Mike Pearlman, Wolfgang Schlueter, Bob Schutz, Wolfgang Seemueller, Peter Shelus

IERS Update:

Peter Shelus reported on the IERS Workshop that had been held at the Paris Observatory on April 18 and 19. The Workshop dealt with those IAU 2000 Resolutions that require actions from the IERS. Resolutions B1.1 and B1.2 concern the celestial reference systems and frames; they reflect the increasing need for more accurate and dense frames, in different wavelengths, with respect to which the motions and rotations of celestial bodies are observed. Resolutions B1.3, B1.4 and B1.5 concern the use of general relativity in astrometry and celestial mechanics to accommodate increasing observational accuracy. Resolution B1.6 concerns the new precession-nutation model that was prepared by the IAU Working Group on Non-rigid Earth Nutation Theory. Resolutions B1.7 and B1.8 concern the transformation between the terrestrial and celestial reference systems; they define the new pole and origins that replace the Celestial Ephemeris Pole, equinox and zero meridian. Resolution B1.9 concerns the new definition of Terrestrial Time in the frame of general relativity. Resolution 2 concerns Coordinated Universal Time (UTC); a working group of the IAU has been established to reconsider the necessity of leap seconds and propose a possible redefinition of UTC. A great deal of very heated discussion took place during the Workshop on the advisability of implementing all of these resolutions within the IERS beginning on 1 January 2003. Great concerns were raised on behalf of the various users of IERS products, as well as questioning whether various analysis centers would be able to make the changes required in a timely and cost effective manner. There were also concerns raised on why the resolutions were to be implemented so quickly within the IERS, prior to the resolutions being adopted by the IAG and the IUGG. A full review of the matters discussed at the IERS Workshop.

IAG Update:

Ron Noomen updated us on the new structure of the IAG, to be ratified during the 23rd general Assembly of the IUGG (July 2003, Saporro, Japan). The new IAG structure will include Commissions (Reference Frames, Earth Rotation and Geodesy, Applications and Engineering, and Gravity Field), Services (IGS, ILRS, IVS, IERS, PSMSL, etc.), Projects, Communications and Outreach, and Intercommission Committees. Although there were concerns on the duplication of activities, the IERS Directing Board approved the new structure of the IAG during their meeting on April 20. The first project being organized is the Integrated Global Geodetic Observing System (IGGOS) that will combine elements of climate, oceans, and solid Earth using measurements of Earth rotation, positioning, and gravity field. The full scope of IGGOS is not yet clear, but the ILRS has been invited to an IGGOS organizational meeting on May 27 in Washington DC. Hermann Drewes was asked to convey our acceptance at the IAG Executive Committee. Mike Pearlman will represent the ILRS at the May 27 meeting as requested. It is intended to have a pilot phase of IGGOS underway by the beginning of 2003.

Action - GB: A follow up letter expressing our intention to participate should be sent to Professor Beutler, the IAG vice-president and leader of the IGGOS working group.

The role and status of the CSTG, presently the only inter-service forum for the measurement techniques, within the new IAG structure is presently unclear.

A new product format, SINEX 2.0, incorporating many of the user comments on shortcomings of SINEX 1.0, is being finalized for implementation.

Working Group Reports:

Networks and Engineering (Werner Gurtner)

In order to enhance data reliability, the NE W/G recommended that the ILRS adopt a minimum content of six data points per normal point for nighttime ranging and three data points for day light ranging. The recommendation included a caveat that fewer data points would be acceptable on lower satellites (5-second normal points) from those systems with lower pulse repetition rates. The GB accepted this unanimously.

Action - CB: Update the web definition of normal points and inform the stations.

The on-line "near real-time" distribution of time biases and other tracking information, implemented by AIUB, and presently in use by EUROLAS, is working very well. The NE W/G recommended that it be implemented worldwide and that we make every effort to further speed up network data submission and delivery to make the on-line information as fresh as possible. The Board directed the CB to look into the feasibility and impact on stations of speeding up the data delivery schedule. The CB will urge all ILRS stations to explore and use the updated time bias information.

Action - CB: Urge the stations to try the on-line facility for "near real time" distribution of time biases and other tracking information and explore options for speeding up data throughput.

Data Formats and Procedures (Wolfgang Seemueller)

In response to both user and engineering requests, it was recommended that we archive and make available full rate data. The CDDIS already archives such data from the NASA stations, and EDC does it for some EUROLAS stations, which send their full rate data to EDC. The GB agreed and a small study group, Wolfgang Seemueller, Carey Noll, and Werner Gurtner was set up to work out the details.

Action - Full Rate Study Group: Work out details for full-rate data submission, archive, and access system.

Analysis Working Group (Ron Noomen)

The Position and Earth Orientation Pilot Projects continue toward the development of ILRS products for the user community. The Etalon Campaign to date has more than doubled the data yield on the two satellites, attributed to both more passes tracked and more segments per pass. The analyses to date indicate only a small improvement (5%) in the quality of Earth Orientation Parameters, and that the improvement could be attributable merely to the increase in total data yield. When the Analysis Working Group meets on April 29 and 30, it will discuss future plans with Etalon and whether they would like the campaign to continue. The significance of this 5% improvement was questioned, and it was recognized that other applications such as GM, station characterization etc, were not pursued yet but should be strongly considered in any request to continue the campaign, which has consequences for the data yield on other high satellites such as GPS and GLONASS.

New Tracking Approval:

The Reflector Satellite is being tracked under an emergency campaign to demonstrate the usefulness of a distributed retroreflector array in determining satellite attitude. The IPIE in Russia was invited to give us an update on their progress to date, to determine whether the experiment was useful. Unfortunately no one from the project was able to attend. The CB will contact the satellite owners to give them an opportunity to respond quickly with a written progress report. In the meantime, the campaign will continue on the emergency basis. At the request of the IPIE, some full rate date (NASA Stations) has been made available through the CDDIS for analysis.

Action - CB: Request a status report from IPIE on the progress of the REFLECTOR experiment.

The IPIE in Russia has requested that the ILRS track the Meteor-3M satellite to support the on-board atmospheric measurements and the testing of a new spherical retroreflector. Although the orbit requirements are not very stringent, the need became more urgent when the radio tracking system failed in early April. The Board agreed to track Meteor-3M at its altitude determined priority, but to instruct the stations that only one pass a day was necessary.

Action - CB: Place Meteor-3M on the priority schedule and inform the stations and IPIE.

Data Usage:

We still have not received a written requirement from IERS on their data requirements from SLR.

Action - Ron Noomen: Contact the IERS and see what is delaying their requirement.

ILRS has had no progress report from IGLOS.

Action- CB: Request a status report from IGLOS on the use of the SLR data

It was suggested that we should get more feedback from the data users on the SLR applications. Reports presently come in the form of short presentations at the ILRS meetings. Possibilities suggested included written reports to be included in the ILRS Annual Report and enhanced user surveys.

Report on Status and Future Plans:

Based on his experience with IVS, Wolfgang Schlueter strongly recommended that we develop a report on ILRS status and future plans. We should know more about what our users are doing with the SLR data and where we see ourselves in the future. What future roles do we foresee for the ILRS and SLR? The IVS developed such a document and believes that, although it took considerable work, it helped to them to develop a vision for the future.

Action - John Degnan and Mike Pearlman: Examine this more closely and, if appropriate, come up with a plan to proceed

Station Qualification:

The Analysis Working Group has reviewed and accepted the Station Qualification Plan prepared by the CB. As recommended by the CB, Core Stations would be defined as those meeting the Shanghai data criteria. The Analysis Working Group recommended setting the threshold for the Participating Stations at 200 Lageos passes per year, or one-half the Shanghai Lageos Criteria, but with the same quality criteria as for the Core Stations. Those stations below this level would fall into the Associate status. Peter Shelus and Mike Pearlman were asked to write up the full recommendation with the resulting station impact for GB deliberation.

Action - Peter Shelus and Mike Pearlman: Provide a full recommendation with resulting station impact for GB deliberation

Other Items:

The members of the GB were provided with copies of the Agenda for the General Assembly on April 25 and the draft program for the Thirteenth Workshop on Laser Ranging to be held in Washington during the week of October 7 -11, 2002.

The Annual Report for 2000 has been sent out. A full report will be assembled for 2001. The table of contents to the report was provided to the GB members. Contributions are due by May 31.

Elections for the next Governing Board will be conducted by the CB this summer, for completion by the meeting in Washington. Prior to elections, the three networks will be solicited for reconfirmation or replacement of their appointed representatives to the GB.

The next Governing Board Meeting is scheduled for October 9, 2002.

Note: These minutes are also available in Microsoft Word format.