ILRS Home Page

Overview

Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) use short-pulse lasers and state-of-the-art optical receivers and timing electronics to measure the two-way time of flight (and hence distance) from ground stations to retroreflector arrays on Earth orbiting satellites and the Moon. Scientific products derived using SLR and LLR data include precise geocentric positions and motions of ground stations, satellite orbits, components of Earth’s gravity field and their temporal variations, Earth Orientation Parameters (EOP), precise lunar ephemerides and information about the internal structure of the Moon. Laser ranging systems are already measuring the one-way distance to remote optical receivers in space and can perform very accurate time transfer between sites far apart. Laser ranging activities are organized under the International Laser Ranging Service (ILRS) which provides global satellite and lunar laser ranging data and their derived data products to support research in geodesy, geophysics, Lunar science, and fundamental constants. This includes data products that are fundamental to the International Terrestrial Reference Frame (ITRF), which is established and maintained by the International Earth Rotation and Reference Systems Service (IERS). The ILRS develops the necessary global standards/specifications for laser ranging activities and encourages international adherence to its conventions.

Quick Links

Welcome

LAGEOS (LAser GEOdynamics Satellite-1), tracked by SLR since May 10, 1976. (Credit: NASA)

Highlights

24th International ILRS Workshop on Laser Ranging Announcement, Buenos Aires Argentina, Nov 1-6, 2026 Release Date: 08/05/2026

We are pleased to announce that the 24th International Workshop on Laser Ranging (IWLR) will take place in Buenos Aires, Argentina the week of November 1-6, 2026. An SLR school will take place on Sunday, November 1st, followed by the Workshop Monday through Friday. An excursion to the AGGO observatory is scheduled for Thursday afternoon of November 5, 2026. Please note that the meeting is planned as a face-to-face (in person) event.

More information is available at the meeting website, which is as follows: https://bkg.bund.de/en/bkg/events/ilrs-workshop

On the website you will find information about the workshop, including registration fees, venue, conference dinner, accommodations, SLR school, and more. Registration will open soon, followed by abstract submissions. Please note that the website is still under construction in some places. [Some may find it expedient to use a browser other than Firefox, if they encounter certificate issues].

The Workshop is hosted by BKG (Bundesamt für Kartographie und Geodäsie - Federal Agency for Cartography and Geodesy), AGGO (Argentine German Geodetic Observatory), CONICET (the Argentine National Scientific and Technical Research Council), and the National Technical University (Universidad Tecnológica Nacional – UTN).

List of Sessions for the 24th International Workshop on Laser Ranging:

Session 00: Opening Session and Keynote(s)
Session 01: Resilience of the network in the context of GGOS.
Session 02: Lessons learned from 50 years of tracking geodetic satellites: from LAGEOS to LARES-2.
Session 03: SLR for Science: the Terrestrial Reference Frame, Altimetry, and Geophysics.
Session 04: SLR for Gravitation and Relativity.
Session 05: Network and Station Operations, In-sky Safety, and Upgrade.
Session 06: New Applications and Advances in LR technologies.
Session 07: SLR Data Processing, Analysis, Automation, and Quality Control.
Session 08: Lunar Laser Ranging, Deep Space Missions, and Time Transfer.
Session 09: AGGO: Role model of a GGOS station.
Session 10: GNSS, Space Debris, and Other Applications of SLR.
Session 11: Closing Session

Important Dates:

Abstract Submission Deadline: September 15, 2026, 23:59 CEST.
(Regarding abstract submission, please follow the instructions on the meeting website).
Registration Deadline: September 30, 2026, 23:59 CEST.

Special note regarding travel to Buenos Aires during the IWLR:

During the week of the 2026 IWLR meeting and the weeks surrounding the IWLR meeting, the main international airport in Buenos Aires (EZE, Ezeiza International Airport) will be undertaking runway maintenance on their #2 runway, which will close that runway and also reduce the length of the primary runway by a significant amount. As a result, wide-body jets (e.g. Airbus A330, Boeing 777, Airbus A350, Boeing 747) will not be able to take off from EZE at full capacity during that period.

With a couple exceptions, this means that travel to/from Buenos Aires from outside South America will require a stopover somewhere in South America, prior to continuing onward to Buenos Aires on a medium-body aircraft (e.g. Airbus A320/A321, Boeing 737/757). (These stopover airports may be São Paulo, Santiago, Bogota, Rio de Janeiro, Montevideo, etc.). Travelers should make sure they allocate sufficient time (3-4 hrs) to make a transfer at these airports. Onward connection flights are then available to both EZE (Ezeiza International Airport) and to AEP (Aeroparque Jorge Newberry), the two airports near Buenos Aires that serve international, regional and domestic traffic. Please consult with a travel advisor or your airline for more information.

More news...

Recent News

Official ILRS contribution to ITRF2020-u2025 (v101) Released - The ILRS Analysis Standing Committee (ASC) has published the final version of the official ILRS contribution to the ITRF2020-u2025, and made it available to the ITRS combination centers: IGN, DGFI-TUM and JPL.

Read more

LAGEOS, LAGEOS-2, LARES-2 SLR data Provide Refined Tests in Fundamental Physics & General Relativity - Three papers have recently been published using Satellite Laser Ranging (SLR) data that provide further tests in fundamental physics and general relativity.

Read more

Altimetry Satellite Mission News from the 2026 OSTST meeting in Wiesbaden, Germany - The Ocean Surface Topography Science Team (OSTST) meeting held its annual meeting in Wiesbaden, Germany (June 22 – 26, 2026). The first session of the meeting was devoted to summarizing the status for many current and planned altimetry missions. We provide a summary of the mission plans for those missions that include SLR tracking for Precise Orbit Determination (POD) (as well as GNSS and/or DORIS).

Read more

NASA Small Satellite Could Make Global Positioning More Precise - A NASA satellite the size of a suitcase, which aims to merge different observing systems and lead to more accurate mapping of Earth, launched July 7 from the Vandenberg Space Force Base in California aboard SpaceX’s Transport-17 mission.

Read the NASA press release.

Read more