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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Design and Performance of Sampled Data Loops for Subcarrier and Carrier Tracking

Design parameters and resulting performance are presented for the sampled data analogies of continuous time phase locked loops of second and third order containing perfect integrators. Expressions for noise equivalent bandwidth and steady state errors are given. Stability and gain margin are investigated using z plane root loci. Finally, an application is presented for Voyager subcarrier and carrier tracking under the dynamics of the encounters with Uranus and Neptune. For carrier tracking, loop bandwidth narrow enough for satisfactory loop signal to noise ratios can be achieved using third order loops without rate aiding, whereas second order loops would require aiding. For subcarrier tracking, third order loops can be used when the sampling rate is limited to approximately once per second, as in the Baseband Assembly, whereas second order loops sufficiently wide to track the dynamics have stability problems at that sampling rate.

Aguirre, S.↗
NASA NTRS1991

NASA SETI microwave observing project: Sky Survey element

The SETI Sky Survey Observing Program is one of two complimentary strategies that NASA plans to use in its microwave Search for Extraterrestrial Intelligence (SETI). The primary objective of the sky survey is to search the entire sky over the frequency range of 1.0 to 10.0 GHz for evidence of narrow band signals of extraterrestrial intelligent origin. Frequency resolutions of 30 Hz or narrower will be used across the entire band. Spectrum analyzers with upwards of ten million channels are required to keep the survey time approximately 6 years. Data rates in excess of 10 megabits per second will be generated in the data taking process. Sophisticated data processing techniques will be required to determine the ever changing receiver baselines, and to detect and archive potential SETI signals. Existing radio telescopes, including several of NASA's Deep Space Network (DSN) 34 meter antennas located at Goldstone, CA and Tidbinbilla, Australia will be used for the observations. The JPL has the primary responsibility to develop and carry out the sky survey. In order to lay the foundation for the full scale SETI Sky Survey, a prototype system is being developed at the JPL. The system will be installed at the new 34-m high efficiency antenna at the Deep Space Station (DSS) 13 research and development station, Goldstone, CA, where it will be used to initiate the observational phase of the NASA SETI Sky Survey. It is anticipated that the early observations will be useful to test signal detection algorithms, scan strategies, and radio frequency interference rejection schemes. The SETI specific elements of the prototype system are: (1) the Wide Band Spectrum Analyzer (WBSA); a 2-million channel fast Fourier transformation (FFT) spectrum analyzer which covers an instantaneous bandpass of 40 MHz; (2) the signal detection processor; and (3) the SETI Sky Survey Manager, a network-based C-language environment that provides observatory control, performs data acquisition and analysis algorithms. A high level description of the prototype hardware and software systems will be given and the current status of the system development will be reported.

Klein, M. J.↗
NASA NTRS1992

Effects Of Asymmetry Of NRZ Data Signals On Performance

Report presents theoretical analysis of effects of asymmetry in binary non-return-to-zero (NRZ) data signals upon performance of radiotelemetry system. Simple mathematical model predicting overall degradation of bit signal-to-noise ratio of telemetry system derived. Shows degradation increases with asymmetry.

Nguyen, Tien M.↗
NASA NTRS1963

The fm demodulator with negative feedback

This paper describes the design and theory of operation of the wideband FM demodulator with feedback (FMFB receiver) used at the Andover, Maine, earth station for Telstar satellite communications tests. Performance data for the FMFB receiver indicate a clear advantage over the conventional FM receiver in many cases. The principal advantage lies in the ability of the FMFB receiver to raise the threshold at which “breaking” occurs for TV and other wideband signals.

TELSTAR SATELLITE↗
NASA NTRS1963

The satellite traveling-wave tube

The traveling-wave tube amplifier described provides a minimum output power of 3.5 watts at 4.0 to 4.2 gc. Design aspects that lead to lifetimes in excess of 10 years and to tube efficiencies between 35 to 40 per cent are discussed. The tube is focused by an improved version of the single-reversal magnetic circuit. Performance data pertinent to this particular satellite operation are shown. Highlights from the final production run and the subsequent life test serve to illustrate the care with which this TWT has been built.

TELSTAR SATELLITE↗
NASA NTRS1966

State-of-the-Art Study for High-speed Deceleration and Stabilization Devices

Documented aerodynamic deployable decelerator performance data above Mach 1. 0 is presented. The state of the art of drag and stability characteristics for reentry and recovery applications is defined for a wide range of decelerator configurations. Structural and material data and other design information also are presented. Emphasis is given to presentation of basic aero, thermal, and structural design data, which points out basic problem areas and voids in existing technology. The basic problems and voids include supersonic "buzzing" of towed porous decelerators in the wake of the forebody, the complete lack of dynamic stability data, and the general lack of aerothermal data at speeds above Mach 5.

STABILIZATION↗