# Spaceborne LiDAR Systems: Evolution, Capabilities, and Challenges
## 5 LiDAR in Space Missions
### Spaceborne LiDARs for Terrestrial Applications  
Several spaceborne LiDAR missions have been launched to support Earth observation and environmental monitoring. Table 1 summarizes the main missions, detailing the name of the mission, the responsible agency, the deployment platform, the launch year, the LiDAR instrument, the operational status, and the primary scientific objective. Selected missions are discussed in the following subsections, with a focus on the LiDAR instruments and their contributions to spaceborne remote sensing. Representative images and renderings of the deployment platforms are presented in Figure 5. Table 2 provides a basic parameter about the LiDAR instruments used as a payload in the missions of Table 1.  
Figure 5: The selected deployment platforms carrying LiDAR instruments, from the left: LITE instrument on top of the Space Shuttle Discovery, CALIPSO satellite carrying a CALIOP instrument, EarthCARE carrying ALTID and ICESat-2 with ATLAS instrument [112; 113; 114; 115]. \begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline
**Mission** & **Agency** & \begin{tabular}{l} **Deployment** \\ **Platform** \\ \end{tabular} & \
\begin{tabular}{l} **Launch** \\ **Year** \\ \end{tabular} &
\begin{tabular}{l} **LiDAR** \\ **Instrument** \\ \end{tabular} & **Status** & **Primary Objective** & **Cit** \\ \hline STS-64 & NASA & Space Shuttle Discovery & 1994 & LTTE & Completed in 1994 & Test of the spaceborne LiDAR and its related key technologies, investigate the molecular atmosphere, aerosols and clouds & [7,16] \\ ICESat & NASA & ICESat & 2003 & GLAS & Completed in 2009 & Measure ice sheet mass balance: the difference between an ice sheet’s snow input, and the ice loss through melting, ablation, or calving Study the role that clouds and aerosols play in regulating Earth’s weather, climate and air quality & [7,117, 118, 119] \\ CATS & NASA & ISS & 2015 & CATS & Completed in 2017 & Extend global LiDAR climate observations, measure range-resolved profiles of atmospheric aerosol and cloud distributions and properties, testing new LiDAR technologies & [122,123] \\ ADM- & ESA & ADM- & Aeolus & 2018 & ALADIN & Completed in 2023 & Provide global observations of wind profiles with a vertical resolution that meets the accuracy requirements of the World Meteorological Organization (WMO) & [122, 124] \\ ICESat-2 & NASA & ICESat-2 & 2018 & ATLAS & Active & Measure polar ice sheet mass balance, sea ice thickness, and vegetation canopy height better to understand climate change and its impacts & [124] \\ GEDI & NASA & ISS & 2018 & GEDI & Paused & Optimized to measure ecosystem structure - determine how changing climate and land-use impact ecosystem structure and dynamics. Measurement of the canopy structure, biomass and topography. First HSRL in space. Measure aerosol profiles and greenhouse gas (CO\({}_{2}\)) concentrations & [125] \\ Gumang & CAST, CRESDA & Gumang & 2022 & LiDAR & Active & Desider for forest carbon sink observation using both LiDAR and passive sensors. Increase the accuracy and efficiency of carbon dioxide measurements. Detect vegetation biomass, atmospheric aerosols, and chlorophyll fluorescence to view the carbon cycle comprehensively. & [127, 128] \\ EarthCARE ESA, JAXA & EarthCARE & 2024 & ATLID & Active & Observe the vertical profiles of natural and anthropogenic aerosols globally, including their radiative properties and interactions with clouds. Observe the vertical distributions of atmospheric liquid water and ice globally, their transport by clouds, and their radiative impact. Retrieve profiles of atmospheric radiative heating and cooling by combining the retrieved aerosol and cloud properties & [127, 128] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: A list of missions carrying LiDAR instruments for Earth monitoring. \begin{table}
\begin{tabular}{l l l l l l l l l l l l l l l l l} \hline \hline
**Instrument** & **Type** & **PRF [Hz]** & **No. ** & **No. ** & **Channels** & **Lasers** & **Laser.