Spaceborne laser remote-sensing technology has the advantages of high vertical resolution, high accuracy, all-day measurements, and the ability to obtain information that cannot be obtained via traditional passive optical or microwave sensors. With the progress of laser and detection technology, spaceborne laser remote sensing technology with different measurement principles has been developed, such as laser altimeters, aerosol backscattering LiDAR, Doppler wind LiDAR, and differential absorption LiDAR. Spaceborne LiDAR is utilized in many fields, such as deep space exploration as well as Earth, land, and atmosphere observation. The main applications of spaceborne LiDAR include three-dimensional elevation measurements of planets and moons, profiles of atmospheric clouds and aerosols, 3D wind speeds of the atmosphere, concentrations of greenhouse gases, and profiles of the ocean subsurface. Spaceborne LiDAR technology plays an important role in surveying, climate and meteorological research, and environmental monitoring.

The first Laser ALTimeter (LALT) was launched by Japan in 2007 with the lunar exploration satellite SELenological and ENgineering Explorer (SELENE), and it obtained three-dimensional elevation measurements of the lunar orbit for nearly a year. In 2008, India’s first lunar mission, namely, Chandrayaan-1, was equipped with a lunar laser ranging instrument (LLRI) and operated in orbit for ten months to obtain three-dimensional elevation measurements.

In October 2007, China launched its first lunar exploration satellite with the Chang’e-1 Laser Altimeter, which effectively obtained elevation data, including the north and south poles of the moon, for the first time. Moreover, it provided important three-dimensional images of the lunar surface. The Chang’e-2 satellite launched in October 2010 was equipped with the same laser altimeter. The Chang’e-3 lunar mission lander was launched in 2013, and it was equipped with a laser range finder and a laser 3D imaging system to assist the lander in finding the best point on the lunar surface.

In the 21st century, NASA launched several spaceborne LiDAR payloads to measure the global vertical profiles of aerosols and clouds as well as polar ice cover and land elevations. The first Geoscience Laser Altimeter System (GLAS) was launched in 2003. In 2006, the first Cloud Aerosol LiDAR with Orthogonal Polarization (CALIOP) was launched. In 2018, the first six-beam Earth measurement laser altimeter (ATLAS) was launched, and it applied single-photon sensing technology to obtain ice, land, and forest elevation measurements. The European Space Agency (ESA) conducted several spaceborne laser radar missions and launched the first wind LiDAR Atmospheric Laser Doppler Instrument (ALADIN) in 2018. The high-spectrum-resolution LiDAR (HSRL) ATmospheric LIDar (ATLID) was launched in 2024 at 355 nm to measure clouds and aerosols.

In the field of land surveying and mapping, since 2019, China has launched several LiDAR payloads, including the ZY3-02 satellite laser altimeter, GF-7 laser altimeter, and terrestrial ecosystem carbon monitoring satellite (TECIS) multibeam LiDAR. The GF-7 laser altimeter is China’s first long-life laser altimeter with full-waveform sampling. In the field of atmospheric environmental monitoring, China launched the Atmospheric and Carbon Dioxide Detection LiDAR (ACDL) satellite in 2022 for atmospheric carbon dioxide and aerosol monitoring. The ACDL is the first spaceborne carbon dioxide detection LiDAR and the first aerosol-measured HSRL, worldwide. In 2025, a high-precision greenhouse gas comprehensive monitoring satellite (DQ-2) with carbon dioxide measured optical passive and active optical instruments will be installed on the same platform.

The first spaceborne laser altimeter using a xenon lamp-pumped mechanical Q-switched ruby laser was launched by NASA in 1971 during the Apollo 15 mission. Such altimeters have also been applied in the Apollo 16 and 17 lunar missions. The Mars Orbiter Laser Altimeter (MOLA) was launched by NASA in 1996, and it has been in operation for five years. All-solid-state lasers were first used to obtain three-dimensional elevations of the Mars surface. Subsequently, NASA launched the Mercury Laser Altimeter (MLA) in 2004 and the first multibeam Lunar Orbiter Laser Altimeter (LOLA) in 2009.

The long life and high measurement accuracy of spaceborne LiDAR have been verified in orbit, and spaceborne laser remote-sensing technology has gradually realized commercial operations from space demonstrations and will play an important role in future land surveying and mapping, climate and meteorological research, and environmental monitoring. In the past 20 years, China's spaceborne laser remote sensing technology has developed rapidly and achieved world-leading innovation achievements in several fields, thereby serving major national requirements and making important contributions to space-active optical sensors worldwide. In the future, methane-measured LiDAR, multi-beam LiDAR with more than 100 beams, and dedicated ocean-sounding LiDAR will operate in space.