Engineering topics
Publications and source records attributed to Franco, Manuel M..
Method of computing noise temperature in beam waveguide system involves both theoretical and experimental elements. Circumvents problem of computing noise temperature exactly from first principles: in case of typical practical system, noise-temperature problem so complex and difficult exact solution impossible.
Frequency instability of antenna under test determined from measurement of phase deviation between outputs of two antennas. Fiber-optic system used to minimize spurious component of frequency instability contributed by propagation of signal from reference antenna to Allan-variance-measuring instrument. Intended primarily to reveal contributions of wind and air-temperature effects on antenna and beam-waveguide structures to overall frequency instabilities of received signals. Technique simpler, less expensive, potentially capable of providing instability data in shorter measuring times, and more precise.
This article presents techniques for measuring frequency stability of a deep space station that was configured with a new X-band transmitter subsystem to enable high-quality radio science data to be obtained for a Gravity Wave Experiment. The instrument and test procedures for performing frequency stability measurements in the field are described. Test results from measurements made on various transmit receive subsystems, as well as the overall transmit-receive end-to-end systems below the antenna feed horn are presented. The subsystem test data proved to be useful for assessing the frequency stabilities of various subsystems. This assessment design improvements needed to meet stringent frequency stability requirements for forthcoming gravity wave experiments.
Portable microwave test packages used to evaluate a new 34-m-diameter beam-waveguide (BWG) antenna are described. The experimental methodology involved transporting test packages to different focal points of the BWG system and making noise temperature, antenna efficiency, and holography measurements. Comparisons of data measured at the different focal points enabled determinations of performance degradations caused by various mirrors in the BWG system. It is shown that, due to remarkable stabilities and accuracies of radiometric data obtained through the use of the microwave test packages, degradations caused by the BWG system were successfully determined.
Efficiency measurements at 8.45 and 32 GHz (X and Ka bands, respectively) were carried out on the new 34 m diameter beam waveguide antenna now in use at the NASA Goldstone Deep Space Communications Complex. The use of portable test packages enabled measurements at both the Cassegrain and 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 pct was measured; at 32 GHz, 44.89 pct was measured.