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13th International Laser Ranging Workshop
"Toward Millimeter Accuracy"

Scientific Achievements, Applications, and Future Requirements
( R. Noomen and S. Klosko)

Session Summary

Title Primary Author
SLR Contribution to the International Terrestrial Reference Frame Zuheir Altamimi
Time-Variable Gravity Analysis Using Satellite-Laser-Ranging as a Tool for Observing Long-Term Changes in the Earth’s Systems -- Invited Christopher Cox
The Development of NASA Gravity Field Models and their Dependence on SLR – Invited Frank Lemoine
Evaluation of potential systematic bias in GNSS orbital solutions Graham Appleby
Contributions of SLR to the Success of Satellite Altimeter Missions -- Invitedv Remko Scharroo
SLR and the CHAMP Gravity Field Mission -- Invited Rolf König
The SLR Contribution to Precision Orbit Determination in the GPS Era Scott Luthcke
Prospects for an Improved Lense-Thirring Test with SLR and the GRACE Gravity Mission -- Invited John Ries
Lunar Geophysics, Geodesy, and Dynamics -- Invited James Williams
Seasonal Changes in the Icecaps of Mars from Laser Altimetry and Gravity David Smith
Future Interplanetary Laser Ranging: Science Goals and Methods -- Invited Ken Nordtvedt
Geophysical Applications of SLR Tidal Estimates -- Invited John Wahr
Laser Ranging Contributions to Monitoring and Interpreting Earth Orientation Changes -- Invited Richard Gross
Monitoring The Origin of the TRF with Space Geodetic Techniques -- Invited Erricos Pavlis
Absolute Earth Scale from SLR Measurements -- Invited Peter Dunn
First results of the French Transportable Laser Ranging Station during the 2002 Corsica campaign for the JASON-1 calibration and validation experiment Joëlle Nicolas
Preliminary orbit determination of GRACE satellites using laser ranging data Milena Rutkowska

The Workshop opened on Monday with the session on “Scientific Achievements, Applications and Future Requirements”. The session addressed a variety of subjects, nicely articulating the broad spectrum of physical phenomena and problems that can be tackled with the laser ranging technique.

The most important aspect of the laser ranging technique is its absolute character, i.e., the extremely accurate (down to several mm in an absolute sense) observation of the distance between a ground station and a satellite target. A second important element is its simplicity of measurement concept; SLR measures the observable (range) directly. A historic disadvantage, which has improved greatly in recent years, is the global station distribution, with resulting limitations in terms of resolution of certain scientific products. All three elements were discussed in the science session presentations.

A clear and unique scientific study area is the global aspect of the terrestrial reference system, the implementation of which requires an absolute measure of origin and scale. Altamimi discussed these issues in his opening paper on the development of the most recent version of the International Terrestrial Reference Frame and in particular the contribution of SLR. By virtue of its relatively long history, SLR provides a long time-series (in some cases 25-30 years) of solutions for specific parameters. A very good example of this was given in the second paper, by Cox, who addressed specific components in the gravitational parameters of the Earth. Due to the length of the time-series, Cox has been able to pick up unusual variations in the dynamic flattening of the Earth, which may be related to other, more general changes in the characteristics of the Earth (i.e., Global Change). Lemoine addressed the steady contribution of SLR to understanding and modeling the entire gravity field of the Earth, emphasizing the impact on our knowledge of this aspect of System Earth.

Several papers focused on a direct application of the SLR observations, notably the immediate link between a ground station and the satellite, or orbit determination and/or validation. Appleby (presenter) and Otsubo, addressed the use of the absolute SLR observations to better characterize and validate the orbital solutions for radionavigation satellites (GPS, GLONASS). The absolute nature of the SLR observation can be instrumental in determining the exact location and orientation of the antennas aboard the navigation spacecraft for calibration and verification purposes. This was followed by a presentation by Scharroo, on one of the main applications of the SLR technique: orbit determination for altimeter satellites. Scharroo gave an overview of the various altimeter missions that have flown, their orbit determination results and the scientific output in terms of absolute sea-level variations. König et al (presented by Grunwaldt) focused on the recent developments in gravity field estimation, where the new missions (CHAMP and GRACE) using new technologies such as spaceborne GPS receivers, accelerometers, and satellite-to-satellite tracking are making significant progress in the state of our knowledge of the Earth’s gravity field. SLR plays a crucial role in the validation of the solutions, again by virtue of its direct and unambiguous measurement of range to the satellite targets. A presentation by Luthcke et al, on the computation of precise satellite orbits, again, highlighted the importance and unique contribution of the SLR technique for such purposes.

Next there were several papers on the more exotic subjects and applications of laser ranging. Ries et al gave a paper on the consequences of Einstein’s General Law of Relativity and the unique role of SLR to observe this. Next, Williams and Dickey (presenter) gave an overview of the status and scientific contributions of laser ranging to targets on the Moon. Smith gave a presentation on the laser altimetry results that have been obtained on the planet Mars. Nordtvedt addressed application of laser ranging to track and communicate with interplanetary spacecraft.

Wahr et al discussed the application of SLR to measure tidal effects on and inside the Earth and the use of this information to study geophysical properties. Gross gave a presentation on the long-standing role of SLR in the observation of the rotational dynamics of the Earth. Pavlis addressed the contributions of the laser ranging technique to the establishment of the terrestrial reference frame and, in particular, its origin component. The complementary global aspect of this frame, absolute scale, was discussed by Dunn, who highlighted historic developments and elaborated on recent achievements. Nicolas et al shared their experience on the operation of the French Transportable Laser Ranging System (FTLRS) and its support of the Jason-1 calibration/validation (cal/val) experiment. The session was ended with a talk by Rutkowska and Zielinski (presenter) on an SLR-only orbit determination of the GRACE satellites.

The opening session of the Workshop gave a good reflection of the broad range of scientific topics that are supported by the laser ranging technique. In some cases, SLR/LLR are unique; in others they play a very valuable supporting role.

Ron Noomen is ILRS Analysis Coordinator
Steve Klosko is ILRS Science Coordinator


Content Owner and Webmaster: Carey Noll
Responsible NASA Official: Frank Lemoine
Last Updated: February 23, 2024



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