Optical communications performance of hybrid 34-meter microwave antennas

There is considerable interest in determining whether suitably modified versions of existing 34-meter antennas at NASA´s Goldstone Communications Complex, originally designed for X-band (nominally 8 GHz) and Ka-band (32 GHz) operation, could also be used to receive near-infrared optical signals. The robust backup structure of these antennas, together with extremely large collecting apertures and milli-degree pointing capabilities suggest that dual RF/Optical communications may indeed be possible, at optical data-rates approaching 1 gigabit per second (GBPS) from typical Mars distances. Several design concepts have emerged as possible candidates, requiring modifications ranging from polishing and coating of the existing aluminum panels of the main reflector, to significant redesign involving replacement of the panels with optical reflectors. Optical receiver parameters such as collecting area, field-of-view (FOV), and immunity to reflected sunlight differ markedly for each design concept, hence will likely lead to different levels of performance in terms of data-throughput at a given BER, and in terms of the ability to point close to the sun. The communications performance of two candidate design concepts operating under realistic daytime conditions is evaluated, with particular emphasis on spatial and temporal acquisition algorithms and receiver optimization to achieve the best possible communication performance at high data rates.