Engineering topics

Trowbridge, D. L.

Publications and source records attributed to Trowbridge, D. L..

10 records

NASA NTRS1995

System noise temperature investigation of the DSN S-band polarization diverse systems for the Galileo S-band Contingency Mission

This article describes measurements made at all three Deep Space Network 70-m S-band polarization diverse (SPD) systems to determine and eliminate the cause of the 1-K elevation in follow-up noise temperature in the listen-only mode of the SPD systems at DSS 43 and DSS 63. The system noise temperatures obtained after finding and correcting the cause of the elevated follow-up noise temperature are also reported.

Fernandez, J. E.↗

NASA NTRS1990

An 8.4-GHz dual-maser front-end system for Parkes reimplementation

An 8.4-GHz front-end system consisting of a feedhorn, a waveguide feed assembly, dual masers, and downconverters was reimplemented at Parkes as part of the Parkes Canberra Telemetry Array for the Voyager Neptune encounter. The front-end system was originally assembled by the European Space Agency and installed on the Parkes antenna for the Giotto project. It was also used on a time-sharing basis by the Deep Space Network as part of the Parkes Canberra Telemetry Array to enhance the data return from the Voyager Uranus encounter. At the conclusion of these projects in 1986, part of the system was then shipped to JPL on loan for reimplementation at Parkes for the Voyager Neptune encounter. New design and implementation required to make the system operable at Parkes included new microwave front-end control cabinets, closed-cycle refrigeration monitor system, noise-adding radiometer system, front-end controller assembly, X81 local oscillator multiplier, and refurbishment of the original dual 8.4-GHz traveling-wave masers and waveguide feed system. The front-end system met all requirements during the encounter and was disassembled in October 1989 and returned to JPL.

Trowbridge, D. L.↗

NASA NTRS1988

An 8.4-GHz dual maser front end for Parkes reimplementation

An 8.4 GHz front-end system consisting of a feedhorn, a waveguide feed assembly, dual masers, and downconverters is being reimplemented at Parkes as part of the Parkes-Canberra Telemetry Array for the Voyager Neptune encounter. The front-end system was originally assembled by the European Space Agency on the Parkes antenna for the Giotto project. It was also used on a time-sharing basis by the DSN as part of the Parkes-Canberra Telemetry Array to enhance the data return from Voyager 2 at Uranus. At the conclusion of these projects in 1986, the front-end system was dismantled, packed, and shipped to Europe. Part of the system was then shipped to JPL on loan for reimplementation at Parkes for the Voyager Neptune encounter. The system is being redesigned and refurbished for operation at Parkes. Tasks include new microwave front-end control cabinets, a closed-cycle refrigeration data acquisition system, a new noise-adding radiometer system, a front-end controller assembly, and refurbishment of the dual 8.4 GHz traveling-wave masers (TWMs) and waveguide feed system.

Trowbridge, D. L.↗

NASA NTRS1986

Block 2A traveling-wave maser

Two 8.4GHz low-noise traveling-wave masers (TWMS) with effective input noise temperatures of 3.6 to 3.9 K and bandwidth in excess of 100 MHz have been supplied to the Deep Space Network. These TWMs are used on the 64-meter antennas at Deep Space Stations 14 and 43 to meet the requirements of the Voyager Uranus encounter. The TWMs have improved isolator assemblies and new interstage matching configurations to reduce gain/bandwidth ripple. They are equipped with followup Field Effect Transistor Amplifiers as part of the design to meet the 100-MHz bandwidth requirements of very long baseline interferometry.

Trowbridge, D. L.↗

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

Low Noise Amplifiers

One of the great technical challenges facing the Deep Space Network is receiving signals from a severely weight limited spacecraft hundreds of thousands to billions of kilometers from Earth. This weight limitation has always imposed strict limitations on the size of the spacecraft antenna and the amount of transmitter power radiated. The communication burden is placed upon the ground systems of the Deep Space Network which must recover an extremely weak signal in the presence of nearly overwhelming amounts of noise. Two key parameters that determine the signal to noise ratio of a received signal using a deep space station are the collecting area and efficiency of the antenna, and the amount of noise which is generated in, as well as allowed to enter in, the antenna-mounted receiver. These parameters are used to describe the relative ability of a deep space station to receive weak signals. As spacecraft to Earth communication distances have increased, the Deep Space Network engages in a relentless effort to increase the figure of merit through larger and more efficient antennas, higher frequencies, and lower system noise temperature.

Petty, S. M.↗

NASA NTRS1980

X-band, low-noise, traveling-wave maser

The development and performance of X-band traveling-wave maser (TWM) systems with effective input noise temperature of 3.5 K and bandwidths varying from 65 to 108 MHz is discussed. These TWMs are used on the 64-meter antennas at Deep Space Stations 14, 43 and 63 at 8420 MHz to meet the requirements of the Voyager-Saturn encounter. The TWMs use shortened and cooled signal input waveguide to reduce noise and are equipped with superconducting magnets and solid-state pump sources to provide the required stability performance.

Trowbridge, D. L.↗

NASA NTRS1978

Direct-reading group-delay measurement

Technique for measuring modulation signal retardation in microwave components gives direct plot of dependence of delay time on carrier frequency. Recorder sensitivity can be adjusted to give convenient scale factor for group delay. From family of such recordings, it is possible to observe changes in group delay due to temperature, mechanical stress, and other factors.

Trowbridge, D. L.↗

NASA NTRS1978

Swept group delay measurement

Direct recording of group delay measurements on a system under temperature and stress tests employs modulated carrier frequency sweep over an S or X band. Reference path and test paths to separate detectors utilize a power divider e.g., a directional coupler or a hybrid T junction. An initially balanced phase comparator is swept in frequency by modulated carrier over the band of interest for different conditions of temperature and/or mechanical stress to obtain characteristic group delay curves.

Trowbridge, D. L.↗

NASA NTRS1977

Independent gain and bandwidth control of a traveling wave maser

An X-band traveling wave maser of the folded-comb type is presented, with two figure-eight coils for gain and bandwidth control. One figure-eight coil covers the full lengths of the comb structure for bandwidth adjustment of an external magnetic field. The other coil covers a central half of the comb structure for independent gain adjustment of the external magnetic field. The half of each figure-eight coil at the turn around end of the comb structure is oriented to aid the external magnetic field, and the half of each coil at the input-output end of the comb structure is oriented to buck the external magnetic field. The maser is pumped in the push-push mode with two different frequencies.

Trowbridge, D. L.↗