This article presents the derivation of a new formula for calculating the noise temperature of mirrors in cascade in a beam-waveguide (BWG) system. Resistive and spillover losses of each mirror are taken into account. No simplifying assump- tions are made, and loss factors are not assumed to be unity. Comparison of noise temperatures calculated by the new formula and a simpler approximate formula (used by other authors in the past) shows negligible differences when used to calcu- late noise temperatures of cascaded low-loss mirrors such as those in current Deep Space Network BWG antenna systems.

This article presents the results of a study that shows that approximate formulas that have been used in the past for computing the noise temperatures of reflectors (due to surface resistivity losses) are more accurate than previously believed. In- stead of being accurate only for incidence angles up to 40 deg, the recent study shows that at 8.45 GHz for a flat aluminum reflector the formulas are accurate to 0.0003 K and to 0.5 K for incidence angles up to 89.2 deg for perpendicular and parallel polarizations. Derivations of the exact and approximate noise temperature formulas also are given.

With the advent of cryogenically cooled front-end assemblies, it has become the practice to define antenna system noise temperature at the horn aperture rather than at the low-noise amplifier (LNA) input port. It is not generally known that when the reference port is moved towards the horn aperture, the values of the operating system noise temperature, Top, and effective receiver noise temperature, Te, will always increase. It is also not generally known that, when the horn and waveguide are at cryogenic rather than ambient temperature, as will be shown in two examples in this article, the value of Tia defined at the LNA reference port can be either larger or smaller than the value of Tia defined at the horn aperture. This fact is not obvious from studying approximate formulas that neglect products of the loss factors of the components between the horn aperture and the LNA. In this article, the exact expressions for Top at different ports are derived. The exact and approximate formulas are compared, and calculations are made on a DSN 8.4-GHz (X-band) and DSN 32-GHz (Ka-band) feed system showing the magnitudes of errors that result when using the approximate formula. The magnitudes of errors were about 0.1 K and 1 K for the X- and Ka-band systems, respectively.

This article presents results of studying noise-temperature contributions due to leakage through the holes on perforated panels of the 34-m beam-waveguide (BWG) and 70-m antennas at 32 GHz and above. The noise-temperature contributions for the 34-m BWG antenna were 0.4 K at 32 GHz and increased to about 6 K at 45 GHz. For the 70-m antenna, the noise-temperature contribution was 0.8 K at 32 GHz and increased to about 16.4 K at 47 GHz. The highest frequencies at which the antennas were free of grating lobes were 45 GHz for the 34-m BWG antenna and 47 GHz for the 70-m antenna. It is conventional practice not to use antennas at and above any frequency at which grating lobes are generated.

This article presents tutorial discussions of available and delivered system noise temperatures as well as antenna e‐ciency and how mismatch errors afiect the expected values. Derivation of the mismatch error equations begins with fundamental considerations, and subsequent steps are purposely presented in detail. Mismatch errors are shown to be functions of the voltage re∞ection coe‐cients of the ambient load, antenna, and receiver. The errors can also be functions of the receiver correlation coe‐cient. Plots are presented showing how each of these coe‐cients afiects deviations of the true operating-system noise-temperature values from the assumed matched-case values for a typical DSN receiving system at 8.45 GHz (X-band).

This article presents the derivations of both the exact and approximate equations for determining the follow-up receiver noise temperature from measured output powers when the first-stage low-noise amplifier (LNA) power supply is turned on and off. Although approximate equations have been used by DSN engineers since the early 1960s when the LNA was a maser, it is important to know whether the equation and experimental procedure are still valid when the LNA is a cryogenically cooled high-electron mobility transistor (HEMT) rather than a maser. In this article, it is shown that the approximate equations and experimental procedure being used for masers can also be used for HEMTs for obtaining an accurate value of the follow-up receiver temperature. However, if the first stage amplifier is not cryogenically cooled, but is at room temperature, it is shown that, if the approximate equation is used, a correction factor (also derived in this article) might have to be applied in order to get an accurate value. Since the derivations do not appear to be documented in any reports, the equations are rederived and presented in this article.

This article presents the results of tests performed to verify predicted sources of receive antenna gain-to-system noise temperature ratio (G=T ) improvements for the DSS-13 beam-waveguide antenna. The sources that gave the most improvement were (1) covering holography adjustment holes with aluminum-tape circular disks, (2) covering all panel gaps on the main-re∞ector surface with aluminum tape, and (3) installing a liquid-nitrogen load to capture stray signals that normally would be absorbed by an ambient environment. The total measured improvement for all sources of improvement tested was 1.2 K at 8.420 GHz and 2.9 K at 32 GHz. The improvement was larger at 32 GHz because a liquid-nitrogen load test was not performed at 8.420 GHz. I. Introduction The Deep Space Network (DSN) consists of an array of large antennas located worldwide for deep-space communication. Improving the G=T of these antennas and their associated receive subsystems translates into increasing the ground received-signal-to-noise ratios. The symbol G refers to the receive antenna gain and T refers to the system noise temperature. The primary objectives of the G=T improvement task are to (1) identify sources where G=T improvements can be made and (2) verify the predicted values through analysis or experimental work. For convenience, in this article the terms system temperature and operating system temperature, Top, will be used interchangeably to mean system-noise temperature, and the terms S-, X- and Ka-band will be used to refer to center frequencies of 2.295, 8.420, and 32 GHz, respectively. Although the goal is to simultaneously improve bothG andT , the experimental work was restricted to testing only improvements of system temperature. Any receive-system gain changes caused by a change in test conflguration are assumed to be negligibly small or to be predictable through theoretical calculations.

This article discusses the development of a net designed to keeps birds out of the 34-m beam-waveguide antenna opening on the dish surface. Test results on a prototype net showed that the net did not deteriorate when 20 kW at 7.165 GHz were transmitted through it. When dry, the worst-case net contribution to the system-noise temperature was measured to be 0.04 K and 0.18 K at 8.425 GHz and 32 GHz, respectively. When wet, the worst-case net contributions were 0.4 K at 8.425 GHz an d3Ka t 32GHz.

This article presents the results of tests performed to verify predicted sources of receive antenna gain-to-system noise temperature ratio (G=T ) improvements for the DSS-13 beam-waveguide antenna. The sources that gave the most improvement were (1) covering holography adjustment holes with aluminum-tape circular disks, (2) covering all panel gaps on the main-re∞ector surface with aluminum tape, and (3) installing a liquid-nitrogen load to capture stray signals that normally would be absorbed by an ambient environment. The total measured improvement for all sources of improvement tested was 1.2 K at 8.420 GHz and 2.9 K at 32 GHz. The improvement was larger at 32 GHz because a liquid-nitrogen load test was not performed at 8.420 GHz. I. Introduction The Deep Space Network (DSN) consists of an array of large antennas located worldwide for deep-space communication. Improving the G=T of these antennas and their associated receive subsystems translates into increasing the ground received-signal-to-noise ratios. The symbol G refers to the receive antenna gain and T refers to the system noise temperature. The primary objectives of the G=T improvement task are to (1) identify sources where G=T improvements can be made and (2) verify the predicted values through analysis or experimental work. For convenience, in this article the terms system temperature and operating system temperature, Top, will be used interchangeably to mean system-noise temperature, and the terms S-, X- and Ka-band will be used to refer to center frequencies of 2.295, 8.420, and 32 GHz, respectively. Although the goal is to simultaneously improve bothG andT , the experimental work was restricted to testing only improvements of system temperature. Any receive-system gain changes caused by a change in test conflguration are assumed to be negligibly small or to be predictable through theoretical calculations.

The last of a series of three articles on the subject, this flnal paint study arti- cle presents excess noise temperatures and added-gain losses at 32 GHz for various combinations of paints and primers currently being studied for use on DSN an- tenna re∞ector surfaces. It is shown that 500FHR6 acrylic urethane-based paint has the lowest excess noise-temperature contribution and should be used for all new DSN beam-waveguide antennas being constructed and for all those 34-m and 70-m antennas whose re∞ector surfaces need repainting.

In past years, it was known that paint on re∞ector surfaces causes degradation of antenna gain and noise temperatures, but it was not known how much degradation occurs as a function of paint and primer thickness or frequency. This article presents an approach used to study the properties of paint by flrst measuring the complex dielectric constants of paint and primers at frequencies of interest. After the complex dielectric constants become known, theoretical calculations then can be made of degradation of antenna gain and noise temperatures due to paint/primer thicknesses as functions of incident-wave polarization and incidence angles in free space. Tables are presented for measured complex dielectric constants over a frequency range from 24 through 34 GHz for (1) the paint and primer currently being used on DSN antenna main and subre∞ector surfaces and (2) paint and primer that are candidate replacements.

The conventional way of expressing power loss in decibels/meter for a multimode waveguiding system with finite wall conductivity (such as a beam-waveguide (BWG) system with protective shroud) can be incorrect and misleading. The power loss (in decibels) for a multimode waveguiding system is, in general, not linearly proportional to the length of the waveguide. New power-loss formulas for multimode system are derived in this paper for arbitrarily shaped conducting waveguide tubes. In these formulas, there are factors such as [exp(jx)-1]/(jx), where x=(/spl beta//sub a/-/spl beta//sub b/)l, with /spl beta//sub a/ and /spl beta//sub b/ being the propagation constants of the different propagating modes and l being the distance from the source plane to the plane of interest along the guide. For a large BWG supporting many propagating modes, /spl beta//sub a/'s are quite close to /spl beta//sub b/'s, thus the mode coupling terms remain important for a very long distance from the source plane. The multimode power loss formula for a large circular conducting tube has been verified by experiments. This formula was also used to calculate the additional noise temperature contribution due to the presence of a protective shroud surrounding a millimeter-wave BWG system.

This article presents a set of theoretical and measured zenith-antenna noise tem- peratures at 8.45 GHz for the DSS-13 34-m beam-waveguide antenna when horns of difierent gains are installed at F1. The methodology for calculations is shown in detail. The major difierences between calculated and measured values are at- tributed to changes in subre∞ector support leg scattering when illuminated by the various horns.

An analytical expression is presented for calculating the effects of multipath on group delay. The expression was experimentally verified by the tests made at the Telecommunications Development Laboratory of the Jet Propulsion Laboratory using the Mariner Venus/Mercury 1973 radio frequency subsystem, block 3 receiver, and the Mu 1 ranging machine. The motivation for the research is explained, and the results are put in the context of other applications to antenna and time-delay measurements.

The results of X-band noise temperature tests on two types of antenna surface panels are presented. The first type tested was a solid antenna panel, while the second type was a perforated panel with 3/16-in.-diameter holes. Measurements were made at 8.45 GHz using an X-band radiometric system. Included in this article are measured noise temperature contributions from: (1) thermal diffusive white paint on solid and perforated panels, and (2) water sprayed on both painted and unpainted perforated panels. Experiments on perforated panels were restricted to the 3/16-in.-diameter hole panels formerly used on Deep Space Network 64-m antennas. Rigorous calibration equations, applicable to a variety of antenna panel and dichroic plate test configurations, are presented. It was demonstrated that an accurate, stable radiometric measurement system of the type used for the results of this research makes it possible to obtain information that would be much more difficult to obtain using other techniques.

A description is given of the dual coupler configuration which was installed at DSS 14 for station delay calibrations during the Voyager era. The Z correction values determined for these new and previous configurations are presented.