Publications

NASA's Orion Artemis II Optical Communications System (O2O) will provide operational laser communications between the ground and lunar orbit for the Artemis II crewed mission. In this work we describe a 40 W ground-based laser transmitter for the O2O system. The uplink transmitter operates in the optical C-band and uses an energy-efficient 32- PPM modulation format. Four spatial diversity channels are time-aligned and combined in the far field. Each channel produces up to 10 W of output power and contains both the communications signal and the 7 kHz modulated beacon signal required for acquisition. The transmitter delivers data at 10 Mbits/s and 20 Mbits/s channel rates, corresponding to the 250 MHz and 500 MHz slot rates respectively.

Demand for increased capacity in deep-space to Earth communications systems continues to rise as sensor data rates climb and mission requirements expand. Optical freespace laser communications systems offer the potential for operating at data rates 10 to 1000 times that of current radiofrequency systems. A key element in an optical communications system is the Earth receiver. This paper reviews the design of a distributed photon-counting receiver array composed of four meter-class telescopes, developed as a part of the Mars Laser Communications Demonstration (MLCD) project. This design offers a cost-effective and adaptable alternative approach to traditional large, single-aperture receive elements while preserving the expected improvement in data rates enabled by free-space laser communications systems. Key challenges in developing distributed receivers and details of the MLCD design are discussed.