Optimization of a Deep-Space Ka-Band Link Using Atmospheric-Noise-Temperature Statistics

Statistics for atmospheric-noise-temperature data at a 31.4-GHz frequency were calculated for the Madrid and Goldstone Deep Space Communications Complexes from the data collected by the water vapor radiometer. These data consist of 74 months of measurements at Madrid and 46 months of measurements at Goldstone. The statistics then were used to optimize a deep-space 32-GHz (Ka-band) link at each site in terms of return data volume at a 30-deg elevation. The atmospheric-noise value obtained through this optimization then was used to calculate the Ka-band return-data volume advantage over 8.4 GHz (X-band) as a function of elevation for a 34-m beam-waveguide antenna at each site. It was observed that, for both sites, the Ka-band advantage is maximized at a 60-deg elevation, providing from 7 to 8.4 dB more data than that provided by a 90 percent weather X-band link, depending on the antenna configuration. At lower elevations, this advantage is reduced to 4 to 5 dB. Finally, the average return-data volume advantage for Ka-band was calculated over two actual elevation trajectories. For the high-elevation trajectory, Ka-band offers an advantage of 6.5 to 7.8 dB more data volume at Madrid and 6.6 to 7.9 dB more at Goldstone, depending on the antenna configuration. For the low-elevation trajectory, Ka-band offers an advantage between 5.7 and 6.8 dB in Madrid and between 5.7 and 6.9 dB at Goldstone.