Laser communication terminals for data relay applications: Todays status and future developments

Laser Communication Terminals are now applied in commercial satellite communication systems. The European Data Relay System (EDRS) is relying on optical intersatellite links at a data rate of 1.8 Gbps for its commercial data relay service. As of today, for data relay applications, there are two LCTs on board of GEO satellites and four LCTs on board of LEO satellites. Since end of 2016, the EDRS service is operational. In this paper, the key design elements of the Laser Communication Terminal (LCT) are presented and an overview of the in orbit experiences will be given. The focus of the paper is on the new LCT data relay development activities both on the user side as well as on the GEO side. The SMART LCT has the target to significantly reduce complexity on the user side. It is the goal of the so-called next generation GEO LCT (NGGL) development to expand the data relay application to global GEO rings and to broaden the user base. Furthermore, the operational efficiency of the data relay system will be improved. For both terminals, the key parameters and related design considerations will be given.