The Spectrum Engineering Group conducted a series of terrestrial interference tests at Goldstone, California, on October 23-25, 2009, using Deep Space Station (DSS)-13 to receive at 32 GHz. The role of interfering emitter was played by a 1-W transmitter and a 1-m dish antenna. Three locations were used for the emitter: 2.1 km distant from DSS-13 with line of sight (LOS), 3.8 km distant without LOS, and 32.4 km distant without LOS. At the two latter locations, the LOS was blocked by hills near DSS-13. At each location, the emitter antenna was first pointed toward DSS-13 and the power received at DSS-13 was measured. (For the locations without LOS, the emitter antenna was pointed along the great circle path toward DSS-13.) Then the emitter antenna was pointed away from DSS-13 along an azimuthal direction (that is, horizontally) in order to measure the resulting decrease in received power. Measured data indicated that when the emitter antenna was pointed toward DSS-13, the measured received power agreed to within about 3 dB of the calculated received power. The calculated received power was based on the propagation loss models of the International Telecommunication Union (ITU). More importantly, it was found that when the emitter antenna was pointed away from DSS-13, the received power decreased more slowly with azimuthal angular offset for the two locations with no LOS, relative to the LOS case. The lesson from this is that for Deep Space Network (DSN) antennas to be adequately protected from trans-horizon interferers, interferer antennas should be pointed away from the great circle path to the DSS by a substantial offset.

A KA -band atmospheric noise temperature and attenuation statistical model is developed for Goldstone, based on water vapor radiometer measurements at 31.4 GHz made during winter and spring 1981. An equivalent X-band model is derived from these measurements, and the two sets of data are compared to determine the possible advantages of developing DSN telecommunications links at 32 GHz. For a nominal elevation angle of 30 degrees and identical antennas, it is found that a KA -band system at Goldstone will show a 5 to 10 dB signal-to-noise ratio advantage over an X-band system more than 99 percent of the time.

Two uncertain factors affecting a telecommunication system’s performance are effective antenna gain and system noise temperature. For an Earth-geostationary satellite–Moon system, they are attributed to the atmospheric attenuation and radiation. In the super-high frequency band, the attenuations are mostly weather related and have the same values for both upward- and downward-propagating signals, while brightness temperatures have different effects for upward- and downwardlooking antennas. In this study, six link scenarios for this system are analyzed. Analysis of atmospheric attenuation and brightness temperatures for each link are presented. This study also discusses the general methodology for determining the noise temperature for a receiving antenna pointing to a blackbody of a given angular extent. A set of curves is presented that is independent of the sizes and brightness temperatures of black bodies. Antenna noise temperature increases are calculated as a function of distance between the antenna beam center and the blackbody disk center normalized by the disk radius. To show an example, these ratios are applied to a case of an Earth-based antenna looking toward the Moon.

Radio noise emissions seen by a spacecraft orbiting Mars or a lander located on the Martian surface are expected to be from Mars’ atmospheric emission, surface noise, and extra-Martian sources. Compared with Earth, Mars has lower surface temperatures and much lower atmospheric absorption and radiation. However, Mars has higher surface emissivity due to the roughness of soil and rocks. Because of very low atmospheric density and optical depth, Mars’ atmospheric emission from oxygen and water vapor is almost negligible. The upwelling brightness temperature at Mars is caused mainly by its surface temperature, with strong local time and latitudinal dependence. Downwelling brightness temperature is dominated by sky temperature. The actual radio noise contributing to the antenna temperature is also a function of antenna orientation, elevation angle, and gain pattern. Assuming a dish antenna with 1-m diameter, for a downward-looking antenna the total noise temperature is about the same as the Earth’s for all frequency bands of interest, with ±15 percent deviations. For an upward-looking antenna, the noise temperature is less than half that of Earth.

Ground antennas are the major visible components of NASA's Deep Space Network (DSN). The role, key characteristics, and performance of these antennas in deep-space telecommunications are described. The system analyses and tradeoffs to optimize the overall ground-to-spacecraft link and to define future missions are elaborated from an antenna perspective. Overall performance of receiving systems is compared using the widely accepted G/T figure-of-merit, i.e., net antenna gain divided by the operating system noise temperature. Performance of past, present, and future antennas and receiving systems is discussed, including the planned development of a worldwide network of 34-m-diameter beam-waveguide antennas. The need for multifrequency operation, presently at S- and X-bands, and in the future at Ka-band, is discussed. The resulting requirements placed on antenna technology are highlighted. Beam-waveguide antenna performance to further improve performance and operational advantages is discussed.

Efficiency measurements at 8.45 and 32 GHz (X- and Ka -bands) have been carried out on a new 34-m-diameter beam-waveguide antenna now in use at the NASA/JPL Goldstone Deep Space Communications Complex. The use of portable test packages enabled measurements at both the Cassegrain and the beam-waveguide focal points. Radio sources (quasars and Venus) were used as calibrators, and updated determinations of flux and source size correction were made during the period of the measurements. Gain and efficiency determinations as a function of elevation angle are presented, and the effects of the beam-waveguide system and antenna structure are clearly seen. At the beam-waveguide focus, an 8.45-GHz peak efficiency of 72.38% was measured; at 32 GHz, 44.89% was measured

Radio frequency interference (RFI) from the DSS 14 Goldstone Solar System Radar (GSSR) was investigated at DSS 12 and DSS 16 with the goal of assisting in the choice of the location of future DSN antennas. Total power measurements at both locations were made at the S-band carrier frequency of 2320 MHz. X-band measurements at the carrier frequency of 8495 MHz could not be made. Exciter-chain output spectrum and klystron output spectrum measurements were made at S- and X-bands using a probable worst-case modulation of the radar signal (short pseudorandom number (PN) code length and short pulse length). Based on these measurements, it is estimated that RFI levels in the DSN receiving bands at both sites (above 10-deg elevation) would be below -192 dBm for a 1-Hz bandwidth

Aperture efficiency measurements made during 1988 on the three 70-m stations (DSS-14, DSS-43, and DSS-63) at X-band (8420 MHz) and S-band (2295 MHz) have been analyzed and reduced to yield best estimates of antenna gain versus elevation. The analysis has been carried out by fitting the gain data to a theoretical expression based on the Ruze formula. Newly derived flux density and source-size correction factors for the natural radio calibration sources used in the measurements have been used in the reduction of the data. Peak gains measured at the three stations were 74.18 (plus or minus 0.10) dBi at X-band, and 63.34 (plus or minus 0.03) dBi at S-band, with corresponding peak aperture efficiencies of 0.687 (plus or minus 0.015) and 0.762 (plus or minus 0.006), respectively. The values quoted assume no atmosphere is present, and the estimated absolute accuracy of the gain measurements is approximately plus or minus 0.2 dB at X-band and plus or minus 0.1 dB at S-band (1-sigma values).

The X- and S-band system operating noise temperatures of the Deep Space Network (DSN) 70-m antennas are presented. Models of atmosphere and ground noise temperature contributions, as they affect the antenna calibrations, are given for future use in telecommunications link modeling. The measured 70-m antenna network gain/system noise temperature (G/T) performance is presented. Compared with the earlier 64-m antenna network, G/T improvements of from 1.8 dB to 2.5 dB, depending on elevation angle, were achieved. G/T comparisons are made with the DSN/Flight Project Design Handbook and the Voyager telecommunications design control table. Actual Voyager telecommunications link performance is compared with predictions made by TPAP (the Voyager telecommunications prediction and analysis program) and with measured performance of the individual 70-m antennas. A modification in the use of antenna gain, system noise temperature, and atmospheric attenuation in existing telecommunications design control tables is suggested.

The efficiency and noise temperature characteristics of the DSN 64 m antenna network prior to its upgrading to 70 m configuration are documented. The DSS 14 (Goldstone, California) is the last of the three large antennas to be upgraded, and the test results presented document its performance just prior to its downtime during the end of 1987. Antenna area efficiency was found to be somewhat higher at DSS 14 than at DSS 43 (Australia) and DSS 63 (Spain). The peak X-band efficiency was determined to be 49.8 percent (without atmosphere), compared with 45.4 and 45.1 percent for DSS 43 and DSS 63, respectively. The X-band zenith system noise temperature was found to be 1 to 3 Kelvins higher than at the other two stations, depending on which maser was chosen for the measurements. Ascribing efficiency differences to small-scale antenna surface roughness, DSS 14 may be regarded as having a 1.5 to 1.6 mm rms surface as compared to the other two antennas with 1.7 to 1.8 mm rms surfaces.

The X-band system noise temperature near the Sun was measured at the DSS 15, a 34 meter high efficiency (HEF) antenna, in November 1987. Data was taken at angles off the center of the Sun from 0 to 4 degrees. At angles greater than 0.5 degree, the measured results agree with Voyager tracking data taken at solar conjunction in late December 1987. Within the solar disk, at angles lower than 0.27 degree, the temperature measured was lower than the prediction of a model by 30 percent, after adjusting for known receiver nonlinearities. The discrepancy in this extreme case is probably caused by unknown nonlinearities in the receiver, uncertainties in the model, or both. The measurement is nevertheless credible for practically all Sun-Earth-probe angles of interest to deep space missions.

The very satisfactory performance of a conceptual 34-m DSS-12 type HA-Dec antenna feed sysem over the frequency range of 1 to 10 GHz is demonstrated. A seven-feedhorn baseline design is developed which will allow Search for Extra-Terrestrial Intelligence (SETI) investigations using each horn over a 1.4:1 frequency range. A gain/system noise temperature (G/T) figure of merit is calculated for the frequency range of each horn; it is found that system performance down to 20 deg elevation is possible with a G/T degradation of less than 3 dB at every frequency. The design presented here will allow shared but independent antenna use by the Deep Space Network (DSN) and SETI with a minimum of operational impacts to DSN functions and no intrusions into the DSN microwave equipment configuration.