Comparative Study of Optical and Radio-Frequency Communication Systems for a

We have performed a study on telecommunication systems for a hypothetical mission to Mars. The objective of the study was to evaluate and compare the beneflts that microwave|X-band (8.4 GHz) and Ka-band (32 GHz)|and optical communications technologies afiord to future missions. The telecommunication sys-tems were required to return data after launch and in orbit at 2.7 AU with daily data volumes of 0.1, 1.0, or 10.0 Gbits (Gb). Spacecraft terminals capable of de-livering each of the three data volumes were proposed and characterized in terms of mass, power consumption, size, and cost. The estimated parameters for X-band, Ka-band, and optical frequencies are compared and presented here. For all cases, the optical °ight terminal exhibits about 60 percent of the mass of the correspond-ing radio frequency (RF) subsystem. Power consumption is comparable for all three technologies at a 0.1 Gb/day data volume, but the power required at either Ka-band or optical is less than half of the X-band requirement at 10 Gb/day. These beneflts can be obtained only with a suitable investment in reception facilities for Ka-band or optical frequencies. As part of an overall study plan to examine the future of space communications across the solar system, we explored the application of these three design points for other possible destinations and, in particular, for Neptune. Although the data return capability at Neptune is reduced by over two orders of magnitude from the Mars case, the relative comparison between the three bands is little changed. I