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Slobin, S. D.

Publications and source records attributed to Slobin, S. D..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

DSN 34-meter Antenna Optics Analysis for Wideband SETI Investigations

A DSN 34-meter symmetric Cassegrain antenna configuration is examined for wideband use over the frequency range of 1 to 10 GHz, rather than only at the narrow-band operational design frequencies of 2.295 GHz (S-band) and 8.448 GHz (X-band). Aperture efficiency and surface efficiency are calculated as the components determining the gain of the antenna. Noise temperature contributions arise from the ground, atmosphere, and quadripod scattering. These components are calculated as a function of frequency elevation angle to determine a G/T (gain/system noise temperature) figure-of-merit for a nominal 34-meter antenna configuration. A computational method was developed which will enable design of a multi-horn antenna feed system to optimally cover the 1 to 10 GHz frequency range.

Slobin, S. D.↗
NASA NTRS1983

The Deep Space Network: A Radio Communications Instrument for Deep Space Exploration

The primary purpose of the Deep Space Network (DSN) is to serve as a communications instrument for deep space exploration, providing communications between the spacecraft and the ground facilities. The uplink communications channel provides instructions or commands to the spacecraft. The downlink communications channel provides command verification and spacecraft engineering and science instrument payload data.

Renzetti, N. A.↗
NASA NTRS1983

Antennas

Reception of the exceedingly small signals from spacecraft typical of deep space communication requires antennas of enormous size, complexity, and precision. The two Voyager spacecraft each have 20-watt X-band transmitters; and at their Saturn encounter distances from Earth of approximately 1.5 billion kilometers, the power density received on the Earth was less than 10 to the minus 19th power watts per square meters. The thrust in deep-space communications improvement was in the areas of ground and spacecraft antenna size and performance increases, spacecraft transmitter power increase, ground receiving system design, and telemetry information coding. Ground antenna theory, design, and performance as related to the particular problem of receiving spacecraft signals using the Deep Space Network (DSN) is described.

Slobin, S. D.↗
NASA NTRS1983

Atmospheric Effects

The Earth's atmosphere consists mostly of the dry components oxygen (about 21% by volume), nitrogen (about 78% by volume) argon (about 1% by volume), and wet components (water vapor, clouds and rain). Water vapor at 100% relative humidity is approximately 1.7% by volume assuming the U.S. Standard Atmosphere, 15 C, at sea level. A communications link through the atmosphere suffers attenuation from both the dry and wet components. This results in a decreased signal to noise ratio (SNR) of the communications link due to both the signal attenuation and the increased noise temperature resulting from thermal emission.

Stelzried, C. T.↗
NASA NTRS1982

Propagation effects on radio range and noise in earth-space telecommunications

Attention is given to the propagation effects on radio range and noise in earth-space telecommunications. The use of higher frequencies minimizes ionospheric effects on propagation, but tropospheric effects often increase or dominate. For paths of geostationary satellites, and beyond, the excess range delay caused by the ionosphere and plasmasphere is proportional to the total electron content along the path and inversely proportional to frequency squared. The delay due to dry air is usually of the order of a few meters while the delay due to water vapor (a few tens of centimeters) is responsible for most of the temporal variation in the range delay for clean air. For systems such as that of the Voyager spacecraft, and for attenuation values up to about 10 dB, increased sky noise degrades the received signal-to-noise ratio more than does the reduction in signal level due to attenuation.

Flock, W. L.↗
NASA NTRS1982

Microwave noise temperature and attenuation of clouds - Statistics of these effects at various sites in the United States, Alaska, and Hawaii

The microwave attenuation and noise temperature effects of clouds can result in serious degradation of telecommunications link performance, especially for low-noise systems presently used in deep-space communications. Although cloud effects are generally less than rain effects, the frequent presence of clouds will cause some amount of link degradation a large portion of the time. This paper presents a general review of cloud types and their water particle densities, attenuation and noise temperature calculations, and basic link signal-to-noise ratio calculations. Tabular results of calculations for 12 different cloud models are presented for frequencies in the range 10-50 GHz. Curves of average-year attenuation and noise temperature statistics at frequencies ranging from 10 to 90 GHz, calculated from actual surface and radiosonde observations, are given for 15 climatologically distinct regions in the contiguous United States, Alaska, and Hawaii. Nonuniform sky cover is considered in these calculations.

Slobin, S. D.↗
NASA NTRS1982

K sub A-band weather-dependent system performance estimates for Goldstone

A K sub A 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 K sub A band system at Goldstone will show a 5 to 1 dB signal-to-noise ratio advantage oer an X-band system more than 99 percent of the time.

Clauss, R. C.↗
NASA NTRS1982

X-band noise temperature effects of rain on DSN antenna feedhorns

Simulated rain tests were carried out to determine the noise temperature contribution of liquid water adhering to the aperture cover material on both a standard DSN X-band feedhorn and on an S/X-band common aperture feedhorn. It was found that for the particular common aperture feedhorn tested, system noise temperature increases were much greater when the plastic horn cover material was old and weathered than when it was new. The age and condition of the aperture cover material is believed to be a major factor in the amount of degradation experienced by a telecommunications system during rain events.

Slobin, S. D.↗
NASA NTRS1981

The 20.7- and 31.4-GHz atmospheric noise temperature measurements

The 20.7/31.4-GHz water vapor radiometer was used for atmospheric noise temperature mesurements. Tipping curve data and on/off Sun data are compared. During the time of the data collection (7:00 a.m. to 12:20 p.m.), the sky was clear and the ground temperature and humidity varied from 14 C to 24 C and 65 percent to 51 percent respectively. The tipping curve data is felt to be the most accurate.

Slobin, S. D.↗
NASA NTRS1981

Some 20.7- and 31.4-GHz solar disk temperature measurements

The performance of a 20.7/31.4 GHz water vapor radiometer was evaluated with respect to its use in measuring atmospheric noise temperature. Results are in good agreement with the results previously reported at the same frequency.

Franco, M. M.↗
NASA NTRS1981

Microwave noise temperature and attenuation of clouds at frequencies below 50 GHz

The microwave attenuation and noise temperature effects of clouds can result in serious degradation of telecommunications link performance, especially for low-noise systems presently used in deep-space communications. Although cloud effects are generally less than rain effects, the frequent presence of clouds will cause some amount of link degradation a large portion of the time. Cloud types, water particle densities, radiative transfer, attenuation and noise temperature calculations are reviewed and examples of basic link signal to noise ratio calculations are given. Calculations for twelve different cloud models are presented for frequencies of from 1 to 50 GHz and elevation angles of 30 degrees and 90 degrees. These case results may be used as a handbook to predict noise temperature and attenuation values for known or forecast cloud conditions.

Slobin, S. D.↗
NASA NTRS1981

Calculation of atmospheric loss from microwave radiometric noise temperature measurements

Microwave propagation loss in the atmosphere can be inferred from microwave radiometric noise temperature measurements. The relevant equations are given and a derivation and calculation is made assuming various physical models. Comparison is made with the commonly used lumped element atmospheric model (isothermal and uniform loss) and the model with linear temperature and exponential loss distributions. The results are useful for estimating the integral inversion differences due to the model selection. This indicates that the commonly used lumped element atmospheric model is a very good approximation with judicious choice of the effective physical temperature. For the worst case comparison, the lumped element model agrees with the variable parameter model within 0.2 dB up to a propagation loss of 3 dB.

Stelzried, C.↗
NASA NTRS1979

DSN water vapor radiometer: Tropospheric range delay calibration

A discussion is presented of the Deep Space Network water vapor radiometer by means of simultaneous antenna temperature and radiosonde measurements at Edwards Air Force Base. The calibration of radiometer gain and hot load radiometric noise temperature is also described. Calibration equations are given. It is found that with a selected data set, the RMS error is less than 1 cm over a total delay range of 9 to 38 cm. Limitations on the use of the water vapor radiometer are also given.

Slobin, S. D.↗
NASA NTRS1978

DSN water vapor radiometer development: Recent work, 1978

A water vapor radiometer (WVR) was developed that measures the atmospheric noise temperature at two different frequencies near 22 GHz. These noise temperature are used in empirical-theoretical equations that yield tropospheric range delay, in centimeters, through the atmosphere along the beam of the WVR. This range correction is then applied, as needed, to measurements concerning spacecraft range and to VLBI baseline determinations. The WVR design and calibration techniques are discussed.

Batelaan, P. D.↗
NASA NTRS1977

DSN water vapor radiometer development: Recent work

A water vapor radiometer (WVR) was developed which measures the atmospheric noise temperature at two different frequencies. These noise temperatures are used in empirical-theoretical equations which yield tropospheric range delay, in centimeters, through the atmosphere along the beam of the WVR. This range correction is then applied to measurements concerning spacecraft range and to very long baseline interferometry determinations.

Slobin, S. D.↗