Multi-mission capable 1550 nm lasercom terminal for space applications

Abstract

General Atomics Electromagnetics (GA-EMS) has developed a free space optical laser communication terminal (LCT) for space applications. The system operates at 1550 nm and utilizes on-off keying to support a data rate of up to 5 Gbps. The system architecture is expandable regarding total output power and can support links from various orbits up to and including GEO-GEO as predicted from the amplifier testing and link budget analysis. The amplifier is based off of a TRL9 system originally used by GA-EMS for airborne applications that has been redesigned for space applications and is currently TRL6 based on a TVAC test conducted in 2018. The system utilizes a software defined modulation scheme that can change between non-return to zero (NRZ) and return to zero (RZ) to support various cross link distances by transitioning between RZ and NRZ. While the current LCT uses OOK, the architecture can support multiple modulation schemes including DPSK, which was tested as part of the 2018 T-VAC test. The LCT uses a novel acquisition scheme which is introduced here that enables rapid acquisition for systems even when the bus level pointing accuracy is in excess of 350urad. This results in a bus agnostic LCT architecture that can be used on multiple mission without necessitating extensive redesign and qualification. GA-EMS plans to launch two of these terminals in cubesats to host an on orbit demonstration of crosslinks between the two terminals and downlinks to a ground station.