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The International Laser Ranging Service (ILRS) provides global satellite and lunar laser ranging data and their related products to support geodetic and geophysical research activities as well as IERS products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF). The service develops the necessary global standards/specifications and encourages international adherence to its conventions. The ILRS is one of the space geodetic services of the International Association of Geodesy (IAG).

The ILRS collects, merges, archives and distributes Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) observation data sets of sufficient accuracy to satisfy the objectives of a wide range of scientific, engineering, and operational applications and experimentation. These data sets are used by the ILRS to generate a number of scientific and operational data products including:

Earth orientation parameters (polar motion and length of day)
Station coordinates and velocities of the ILRS tracking systems
Time-varying geocenter coordinates
Static and time-varying coefficients of the Earth's gravity field
Centimeter accuracy satellite ephemerides
Fundamental physical constants
Lunar ephemerides and librations
Lunar orientation parameters

The accuracy of SLR/LLR data products is sufficient to support a variety of scientific and operational applications including:

Realization of global accessibility to and the improvement of the International Terrestrial Reference Frame (ITRF)
Monitoring three dimensional deformations of the solid Earth
Monitoring Earth rotation and polar motion
Support the monitoring of variations in the topography and volume of the liquid Earth (ocean circulation, mean sea level, ice sheet thickness, wave heights, etc.)
Tidally generated variations in atmospheric mass distribution
Calibration of microwave tracking techniques
Picosecond global time transfer experiments
Astrometric observations including determination of the dynamic equinox, obliquity of the ecliptic, and the precession constant
Gravitational and general relativistic studies including Einstein's Equivalence Principle, the Robertson-Walker b parameter, and time rate of change of the gravitational constant
Lunar physics including the dissipation of rotational energy, shape of the core-mantle boundary (Love Number k2), and free librations and stimulating mechanisms
Solar System ties to the International Celestial Reference Frame (ICRF)

Recent News

ILRS Data Files for SLR processing have been updated - The ILRS Analysis Standing Committee (ASC) has released updates to the following files:

(1) Data Handling File
(2) Eccentricity Files
(3) SLRF2020 Positions & Velocities

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Cancellation of ILRS Technical Workshop in Arequipa, Peru - Due to circumstances beyond their control, the University of San Agustin (UNSA) will not be able to host the 2025 International Workshop on Laser Ranging at Arequipa in October 2025. The ILRS thanks the UNSA team for all their efforts planning and preparing for hosting the workshop. The ILRS is considering the option of holding a virtual meeting this year (2025) if there is sufficient interest, support for the organization, and approval by the ILRS Governing Board. The ILRS Central Bureau welcomes your thoughts regarding holding a potential virtual ILRS workshop as well as offers to help organize the meeting along with the Central Bureau. The next in-person ILRS workshop will be in Buenos Aires, Argentina in 2026.

ILRS Central Bureau surveys stations on the ILRS Tracking Priority List - In March 2025, the ILRS Central Bureau (CB) conducted a survey of the ILRS stations to try and understand better how stations used the ILRS Priority List. Currently, the ILRS priority list is constructed to according to satellite orbit parameters as well as according to special project needs. The satellite tracking priority is generally arranged by altitude such that the satellites at the lowest altitude (and thus the shortest satellite passes) have the highest tracking priority. While logical, this mode paradoxically places the geodetic ITRF satellites (i.e. LAGEOS-1, LAGEOS-2, LARES-2) at the apparently high tracking priorities of 24, 25 & 18 respectively. In order to provide information that could inform a redesign of how tracking priorities are presented and communicated to the stations, the ILRS CB asked a series of short questions in a short survey. The survey was designed to be anonymous and left the possibility for survey participants to provide more information and other comments.

The ILRS station tracking priority survey results can be found here.

The decommissioned geodetic satellite WESTPAC will be returned to the ILRS target list with a low priority, not resulting in a significant burden to station scheduling or impact on other priority targets. In tests led by the ILRS Network and Engineering Standing Committeee (NESC), ILRS stations have demonstrated that with good predictions Westpac can be tracked routinely during the day and night, without a significant impact on the station tracking schedules or at the expense of other ILRS targets.

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Meetings

Munich Satellite Navigation Summit, Munich, Germany, March 26-28, 2025

FIG Working Week 2025, Brisbane, Australia, April 6-10, 2025

EGU General Assembly 2025, Vienna, Austria, April 27 - May 2, 2025

Publications

2016-2019 ILRS Report

Proceedings from the 19th International Workshop on Laser Ranging

International Laser Ranging Service

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