## 2 Previous Space-Based Laser Communication Missions  
In recent decades, a variety of space missions utilizing optical terminals have been launched for diverse purposes. For instance, the National Aeronautics and Space Administration (NASA) of the United States demonstrated a laser transmission link to the Galileo probe in outer space in 1992, as a part of Galileo Optical Experiment (GOPEX). The communication link used Earth-emitted pulses with megawatt power at a 532 nm wavelength, captured by a camera onboard the Galileo probe around 6 million kilometers away [30]. The first space-to-ground (i.e., GEO to the optical GNS) bi-directional laser communications link was demonstrated by LCE aboard the Japanese Engineering Test \begin{table}
\begin{tabular}{c c c c} \hline
**Platform** & **Project/Experiment** & **Maximum Link Span (km)** & **Maximum Data Rates** \\ \hline LEO to Ground Station & LUCE [13], OPALS, Test LCT links [12] & 5000 & 1.8 Gbps \\ LEO to GEO Satellite & SILEX [14], EDRS [15] & 45,000 & 50 Mbps to 1.8 Gbps \\ LEO to Aircraft & OCSD [9] & 200 & 100 Mbps \\ Aircraft to Ground Station & [21] & 50–79 & 1.25 Gbps \\ Balloon to LEO Satellite & STROPEX [23], CAPANINA [24] & 200 & 2.5 Gbps \\ GEO to Ground Station & LCE aboard ETS-VI [8; 9] & - & 1 Mbps \\ HAP to Ground & Stratobus [2; 29] & 20 km above earth surface & - \\ Ground to Deep Space & LLCD, LCRD [7; 18; 19] & 380,000–400,000 & 620 Mbps to 20 Gbps \\ Deep Sea & JAMSTEC [26] & 0.9 & 1 Gbps \\ Inter-satellite Link & OICETS, SILEX [16], LCRD [17] & 45,000 & 50 Mbps \\ \hline \end{tabular}
\end{table} 
Table 1: An example of optical space communication across various platforms. Figure 1: Architecture of satellite communication systems via different communication link types. Satellite-VI (ETS-VI) satellite in 1994, with a data rate of 1 Mbps, weight of 22 kg, and power consumption of 60 W [8; 9]. Similarly, another milestone in creating the world's first inter-satellite laser communication link was developed, named the Advanced Relay and Technology Mission Satellite (ARTEMIS) by the European Space Agency (ESA). The communication link provided mobile services with a data transfer rate of 50 Mbps and a data relay from French Earth Observation satellite SPOT-4, positioned in LEO, through an optical channel to the geostationary ARTEMIS satellite. Then, the ARTEMIS satellite transmitted the information between the LEO and the GND via radio waves [14; 31]. Likewise, the Optical Inter-orbit Communication Engineering Test Satellite (OICETS) demonstrated LEO to GND inter-orbit laser communication experiments in conjunction with ESA's ARTEMIS, known as \"Ki-rari\", and was a product of the collaborative efforts of the Japan Aerospace Exploration Agency (JAXA) [32]. It showcased an advanced on-orbit pointing, acquisition, and tracking methodologies. Structurally, Kiriar was designed with a three-axis stabilization mechanism, weighing ~570 kg and having a power consumption of 1200 W, which was measured at the end of the satellite's operational life. The optical link can achieve a downlink data rate of 50 Mbps and uplink rates of 2 Mbps at a wavelength of 800 nm. The Kiriar's orbital path is sun-synchronous, characterized by an inclination of 97.8\({}^{\circ}\) that occurs due to its altitude variations, ranging from 550 km at its operational end to 610 km at its commencement [13]. Alternatively, a HAP inter-connected with optical links was initiated by EADS Astrium (currently known as Airbus Group) in collaboration with the French Ministry of Defense's arms procurement division (DGA), in which a seamless laser communication link was established between an optical terminal on-board an aircraft flying at 9 km and the SILEX terminal on the ARTEMIS geostationary satellite. The link characteristics are dictated by the SILEX system, in terms of data rate, which is recorded as 50 and 2 Mbps for downlink and uplink channel, respectively, laser wavelength of ~800 nm and COK (On-Off Keying) modulation [33].