The role of satellite laser ranging in space geodesy: developments, applications and Indian perspective

Satellite laser ranging (SLR) has been a key geodetic technique for over 60 years, contributing to reference frame realisation, Earth orientation monitoring, orbit determination, and gravity field modelling.The International Laser Ranging Service (ILRS) operates a global network of 50 tracking stations, ensuring millimetre-precision measurements for the International Terrestrial Reference Frame (ITRF).However, challenges such as uneven station distribution, atmospheric effects, and retroreflector degradation impact data accuracy.The United Nations (UN) adopted the Global Geodetic Reference Frame (GGRF) resolution in 2015, aiming for 1 mm accuracy and 0.1 mm/year stability; however, the current precision stands at 5 mm and 0.5 mm/year.Advancements such as MiniSLR technology, automation, and high-power kHz lasers enhance precision.India is expanding its SLR capabilities with ISRO-tracked stations at Mount Abu and Ponmudi, alongside colocated geodetic sites at IIT Kanpur's Geodesy Village.The National Geospatial Policy 2022 (NGP 2022) supports the Continuously Operating Reference Stations (CORS) network for horizontal datum definition, strengthening India's self-reliance in space geodesy and terrestrial reference frame realisation.The objective of the present article is to consolidate global and Indian developments in SLR, highlighting its applications in geodesy and India's geodetic future.