# An Overview of CubeSat Missions and Applications
## 4 The Use of CubeSats as Telecommunication and Asset-Monitoring Platforms
### Optical Communication CubeSat Missions and Applications  
Apart from the traditional radio communication technologies, CubeSats in recent years have also begun incorporating laser-optical communication technologies. Optical communication utilizes light as the means of transmitting information over long distances using lasers. Compared to traditional radio communication technologies, laser-optical communications feature several advantages which include the following. First and foremost, due to the higher frequencies of the optical spectrum compared to the radio spectrum, laser-optical communication systems offer the potential for much higher data rates and a better signal/noise ratio in good atmospheric conditions. Thus, for the same data rate,laser-optical communication systems exhibit a considerably smaller size and lower overall power requirements, as well as a greater efficiency compared to radiofrequency-based communication systems. Moreover, since optical communications so far are not subject to international telecommunication regulations, no long-lead licensing authorization activities are needed for signal transmission. Finally, when compared to radiofrequency communication links, laser-optical communication links are considered safer as the narrow laser beam utilized by such systems is much more difficultly detected, intercepted, and exploited by third parties. However, it should be noted that despite their significant array of advantages, laser-optical communications also exhibit certain disadvantages when compared to radio communication technologies. For example, a much higher pointing accuracy is required of the space-platform for the execution of a laser-optical link, which in turn adds cost and complexity to the design and manufacturing of the satellite platform. Furthermore, laser-optical communications are considerably vulnerable to weather-based disruptions such as beam attenuation due to atmospheric absorption and the presence of cloud cover, fog, or rain [184; 185]. The first CubeSat mission ever to attempt the realization of an optical communication link was FITSAT-1, a 1U CubeSat developed by the Fukuoka Institute of Technology for JAXA, which was deployed from the ISS on 5 October 2012. Its main mission involved the high-speed transmission of pictures via a 5.8 GHz microwave and the execution of an experimental low-light-level optical communication link with its ground station by using 50 green and 32 red 3 W LEDs by which it transmitted a 1 kHz Morse code signal. During the mission, the team of the Fukuoka Institute of Technology was successful in detecting the light signal transmitted by FITSAT-1 using a telescope equipped with a photo-multiplier. FITSAT-1 remained operational until its atmospheric reentry on 4 July 2013 [186]. Other examples of past laser-optical communication CubeSats include AeroCube-11A and AeroCube-11B, two 3U spacecrafts which were developed by the Aerospace Corporation under the mission of acquiring multispectral image data of the Earth's surface. The second leg of their mission involved the downlink of the captured images with data-rates reaching 100 Mbps, using an on-board compact laser-optical communication system. The AeroCube-11 CubeSats successfully demonstrated the capability of combining the task of Earth observation with the very-high data transfer rates offered by laser-optical communications technologies inside the limited volume available to a 3U satellite platform [187; 188]. Perhaps the most prominent example of a laser-optical communications CubeSat mission that has been completed up until this point is NASA's Pathfinder Technology Demonstrator 3 (PTD-3) mission, which was launched on 25 May 2022.