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Smith, D.

Publications and source records attributed to Smith, D..

54 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Precision orbit determination at the NASA Goddard Space Flight Center

This paper describes the GEODYN computer program developed by the Geodynamics Branch at the NASA Goddard Space Flight Center and outlines the procedure for accurate satellite orbit and tracking-data analyses. The capabilities of the program allow the development of gravity fields as large as 90 by 90, and a complete modeling of tidal parameters. It is also feasible to numerically integrate a continuous orbit of a satellite such as Lageos for up to 12 years. The evolution of the orbit can be studied, and, by comparison with locally determined orbits, force model improvements can be made. The GEODYN flow diagrams are presented.

Putney, B.↗
NASA NTRS1988

Responsivity of silicon photodiodes from 0.5 to 1.1 micron at 77 K

The responsivities of Si, Ge, and InSb photodiodes at 77 K are measured and compared. The results are used to determine the wavelength at which a change should occur in the detector materials used in the focal plan of the Mars Observer Visual and IR Mapping Spectrometer (VIMS). Quantitative responsivity data for Si photodiodes in the band from 0.5 to 1.1 were needed for the VIMS system analysis. The results show that the Si array for the focal plane should have two different antireflection coatings. It is found that the Si and InSb materials have equivalent quantum efficiencies at about 0.9 microns. Because of unknown signal chain complications that could be caused by a multiplexer accessing two different capacitances, the focal plane was designed with a change from Si to InSb at 1 micron.

Staller, C.↗
NASA NTRS1984

Feedthrough Seal For High-Pressure Vessel

Combination of ceramic and plastic withstands many depressurizations. Stack of washers surrounds leadthrough electrode. Under pressure washers expand to fill leadthrough hole in high-pressure vessel. Seal thus formed withstands 20 or more pressurization/depressurization cycles. Seal composed of neoprene, polytetrafluoroethylene, nylon and high-purity, high-density commercial alumina ceramic.

Williams, R.↗
NASA NTRS1984

Space simulation testing of the Earth Radiation Budget Satellite (ERBS)

The Earth radiation budget components and dynamics and the interactions of this energy cycle, which influences our climate were investigated. The satellite package was subjected to space simulation testing. The size of the spacecraft dictated that the testing be conducted in the new BRUTUS Thermal Vacuum Facility. Computer aided control (CAC), quartz crystal microbalance (QCM), and residual gas analysis (RGA) monitoring are combined with rigid contamination control procedures to protect the flight hardware from anomalous and potentially destructive out of scope test environments.

Magette, E.↗
NASA NTRS1984

Coupled orbiting inertial reference systems and Geopotential Research Mission (GRM) geodesy

Two spacecraft, one following the other with a separation of a few hundred kilometers and orbiting at an altitude of 160 km in a 90-degree polar orbit, are used to detect the minute variations in the earth's gravitational field. Housed in a capacitive cavity located at the centroid of the spacecraft is a free-floating metallic spherical proof-mass, which is the sensor controlling the thrusters that nullify all nongravitational forces on the spacecraft. The proof-mass in each spacecraft is the inertial-guidance reference for its host spacecraft, and the proof-masses are coupled together by a millimeter-wave link. This coupled system detects minute changes in the spacecraft's orbital positions and thus measures the anomalies present in the gravitational field of the earth. To derive a global geodetic model of the gravitational field with an amplitude resolution of 1 milligal and a spatial resolution of 100 km requires that the relative velocity between the proof-mass references be determined to within 1 micron/s.

Keating, T.↗
NASA NTRS1982

Honeywell multispectral linear array (MLA) instrument design A system overview

In support of NASA's Experimental Land Observing System, a simple, reliable and relatively inexpensive multispectral linear array (MLA) instrument concept has been developed. The design satisfies requirements for multichannel radiometry and wide field imaging. A reflective off-axis anastigmat telescope is mounted in a highly strength-to-weight efficient truss structure, coupled to a solid beamsplitter assembly. Attention is given to the optical design of the MLA instrument, the telescope structure, the detector arrays, detector cooling, on-orbit calibration, signal processing electronics, the spacecraft interfaces, the modulation transfer function, the signal-to-noise ratio, radiometric accuracy, and spatial registration.

Eyring, D.↗
NASA NTRS1980

Automation literature: A brief review and analysis

Current thought and research positions which may allow for an improved capability to understand the impact of introducing automation to an existing system are established. The orientation was toward the type of studies which may provide some general insight into automation; specifically, the impact of automation in human performance and the resulting system performance. While an extensive number of articles were reviewed, only those that addressed the issue of automation and human performance were selected to be discussed. The literature is organized along two dimensions: time, Pre-1970, Post-1970; and type of approach, Engineering or Behavioral Science. The conclusions reached are not definitive, but do provide the initial stepping stones in an attempt to begin to bridge the concept of automation in a systematic progression.

Smith, D.↗
NASA NTRS1977

LANDSAT D: Applications development laboratory study

As the Earth Resources Program has matured through the LANDSAT spacecraft it has begun the transition from an experimental research activity to a sound demonstration of proven utility. This important transition will be complete with the LANDSAT D system which incorporates several key improvements over the current system. These improvements, based on experience with the existing LANDSATs, will provide new capabilities in the spacecraft, the sensor, the ground system, and the overall system design.

Alexander, L.↗
NASA NTRS1975

Phase and amplitude scintillations at 9.6 GHz on an elevated path

Deep fading, e.g., greater than 40 dB, was observed at 9.6 GHz on a 150 km path with terminals at 3025 and 3300 m elevations and with no significant illumination of the earth's surface. Fades at two antennas separated horizontally by 100 m were largely uncorrelated. Phase variability was also measured and is presented in terms of spectra and coherency between antennas with 10 m and 100 m horizontal spacing.

Thompson, M. C.↗
NASA NTRS1973

Control of contaminants on sensors. Report 1: Interdirectorate working group on earth observation sensors

Examples of contamination of sensors from various sources during space missions are presented. Design precautions to provide access to optical surfaces and venting of outgassing products are recommended as methods for coping with contamination. The effects of the sensor materials on sensor contamination are analyzed. Actions to be taken during transportation, storage, and testing of sensors to avoid contamination are discussed.

Hovis, W.↗
NASA NTRS1971

Air Force/Ion Physics hardened lithium doped solar cell development

Introduction of lithium by ion implantation eliminates reproducibility and surface problem deficiencies of other introduction techniques. Implantation has been demonstrated to make possible a degree of control over the cell lithium content which has not previously been available. Front barrier development remains to be completed. Successful development of the barrier will make available the freedom to select optimum lithium concentration throughout the cell, including in the vicinity of the junction.

Kirkpatrick, A.↗
NASA NTRS1971

Experiment T002: Manual navigation sightings

Navigation-type measurements through the window of the stabilized Gemini 12 spacecraft by the use of a hand-held sextant are reported. The major objectives were as follows: (1) to evaluate the ability of the crewmen to make accurate navigational measurements by the use of simple instruments in an authentic space flight environment; (2) to evaluate the operational feasibility of the measurement techniques by the use of the pressure suit with the helmet off and with the helmet on and the visor closed; (3) to evaluate operational problems associated with the spacecraft environment; and (4) to validate ground based simulation techniques by comparison of the inflight results with base line data obtained by the pilot by the use of simulators and celestial targets from ground based observatories.

Smith, D.↗
NASA NTRS1968

Brazing alloy Patent

Brazing alloy adapted for brazing corrosion resistant steel to refractory metals, also for brazing refractory metals to other refractory metals

Smith, D.↗