We report the design of OPTEL-D which is an optical communication system for direct data transfer from deep space to earth. OPTEL-D extends the link distances of current optical communication systems to the deep space. The design covers the electrical, thermal, mechanical and optical challenges that such a link distance imposes to both the ground and the space segment. The detailed conceptual system design is presented together with its trade-offs and performance analyses. The space terminal is based on a modular approach which groups the fiber-optical, the opto-mechanical, and the electrical functions into separated modules for independent accommodation. The transmitter beam is provided by an amplitude modulated MOPA system operating at 1.5um. The opto-mechanical unit accomplishes beam forming and steering of the transmit beam as well as reception of the uplink channel. An electrical unit comprises power-conditioning, data-handling, and terminal control through its interfaces to the spacecraft. It is concluded that the OPTEL-D space terminal mass and power are 34 kg and 116 Watts. Depending on the ground station configuration, a data rate of several Mbps is reached over distances of >75 Mio kilometers. Critical assumptions on the receiver sensitivity were verified by tests and the results will be presented. The design of OPTEL-D was derived in collaboration with the European Space Agency to serve the Asteroid Impact Mission. Due to its modular approach using commercially available technology, it can be realized in a competitive schedule and cost frame providing flexible yet powerful data downlinks to most deep space missions.
The OPTEL-μ terminal is designed to transmit data generated on-board LEO satellites to an optical ground station at a data rate of 2 Gbps. This would allow operators of LEO satellites to downlink the large amounts of data being generated by their payload to ground. To make this technology attractive to LEO satellite user community the design of the OPTEL-μ has minimal impact to the spacecraft resources.