This presentation discusses optical satellite communication. It introduces different types of satellites like LEO, MEO, and GEO. GEO satellites orbit above the equator at an altitude that allows around 180 satellites spaced approximately 2 degrees apart. Early communication satellites included Relay, Telstar, and Syncom 2. The presentation covers link design considerations for optical satellite communication like wavelength, polarization, link budgets, pointing, acquisition, and tracking. It provides an overview of a direct detection optical ground terminal, describing its main components - the terminal head unit and remote electronics module. The optical antenna assembly comprises the telescope and coarse pointing assembly. Major challenges for optical satellite communication include positioning satellites in orbit, maintaining stability, power requirements, and operating in the harsh space