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At least 793 records · Page 44

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NASA NTRS1973

Orbital design strategy for domestic communication satellite systems.

Review of some of the considerations pertinent to efficient orbit utilization in the design of domestic communications satellite systems. A strategy is developed to efficiently locate a heterogeneous system of satellites within the available arc and provide room for future growth. A practical design is illustrated, using a computer simulation model, for the placement of 25 satellites within 73% of the available arc employing frequency and polarization coordination techniques. A number of widely variable factors that influence satellite spacing are examined. These factors include such critical system elements as telephony and television interference noise limits, frequency plan coordination, polarization plan coordination, ground antenna diameter, signal protection ratio, and satellite station keeping.

Ramji, S.↗

NASA NTRS1973

Absorption lines in the spectrum of the quasar Markarian 132.

Wavelengths and profiles of several absorption lines in the spectrum of the quasar Markarian 132, obtained with the aid of an integrating television sensor, are presented. An attempt is made to derive column densities and internal Doppler velocities by fitting theoretical Voigt profiles to the observed spectra. C IV lines show that the absorption must occur in at least two separate clouds with a relative velocity of 160 km/sec.

Morton, D. C.↗

NASA NTRS1973

ERTS-1 - Teaching us a new way to see.

The ERTS-1 payload is discussed, giving attention to three television cameras, which view the same area in three different spectral bands. The payload includes also a multispectral scanner subsystem and a data collection system which collects information from some 150 remote, unattended, instrumented ground platforms. Many government agencies use ERTS-1 data as integral parts of their ongoing programs. Through its EROS program, the Interior Department represents the largest single recipient and user agency of data obtained from NASA aircraft and spacecraft designed to gather repetitive information related to a wide variety of earth-science and natural-resources disciplines. Questions of environmental impact are considered together with applications in agriculture, forestry, marine resources, geography, and the survey of water resources.

Mercanti, E. P.↗

NASA NTRS1971

Teleconferencing, an annotated bibliography, volume 3

In this annotated and indexed listing of works on teleconferencing, emphasis has been placed upon teleconferencing as real-time, two way audio communication with or without visual aids. However, works on the use of television in two-way or multiway nets, data transmission, regional communications networks and on telecommunications in general are also included.

Shervis, K.↗

NASA NTRS1972

Mariner 9 control net of Mars, August 1972

Results are presented for a planet-wide geodetic control net of Mars which is based on Mariner 9 pictures as of August 1972. Aerocentric and aerographic coordinate of 809 control points were computed from 407 television frames. Photogrammetric parameters and methodology used in the computations are discussed. The coordinates of the features are given and figures that show the locations of the control points on the surface of Mars are included.

Davies, M. E.↗

NASA NTRS1973

Data storage, image tube type

Method and apparatus for the storage of digital or analog electrical signals are provided by a memory storage system employing a conventional vidicon tube. At the beginning of an operating cycle, the vidicon is conditioned to accept electrical data input by exposing its photosensitive target to a short, high intensity light flash. A first electron beam scan of the photosensitive surface then sets up a charge pattern on the photosensitive target. A second electron beam scan of the photosensitive surface by an unmodulated electron beam then develops an output signal across an output resistor by using capacitive currents. The conditioning and scanning steps are operated repetitively at high speed using conventional television camera scan, sync, and power supply circuitry to provide a low cost data storage system.

Lipoma, P. C.↗

NASA NTRS1973

Surface features on Mars: Ground-based albedo and radar compared with Mariner 9 topography

Earth-based albedo maps of Mars were compared with Mariner 9 television data and ground-based radar profiles to investigate the nature of the bright and dark albedo features. Little correlation was found except at the boundaries of classical albedo features, where some topographic control is indicated. Wind-blown dust models for seasonal and secular albedo variations are supported, but it is not clear whether the fines are derived from bright or dark parent rock. Mars, like the Earth and Moon, has probably generated two distinct types of crustal material.

Frey, H.↗

NASA NTRS1973

On the capabilities of the spin-scan imaging technique

A summary description is made of spin-scanning devices for various space missions. Compared to television, scan-imaging has remarkable advantages and these are listed.

Gehrels, T.↗

NASA NTRS1974

Fixed-base simulation study of decoupled controls during approach and landing of a STOL transport airplane

A fixed-base visual simulation study has been conducted to evaluate the use of decoupled controls as a means for reducing pilot workload during approach and landing of an externally blown jet-flap short take-off and landing (STOL) transport. All six rigid-body degrees of freedom were employed with the aerodynamic characteristics based on wind-tunnel data. The primary piloting task was to use a flight director to capture and maintain a two-segment glide slope, with a closed-circuit television display of a STOL airport used during simulations of the flare and landing. The decoupled longitudinal controls used constant prefilter and feedback gains to provide steady-state decoupling of flight-path angle, pitch angle, and forward velocity. The pilots were enthusiastic about the decoupled longitudinal controls but believed the decoupled concept offered no significant advantage over conventional controls in the lateral mode.

Miller, G. K., Jr.↗

NASA NTRS1974

Apollo experience report: Command and service module communications subsystem

The development of spacecraft communications hardware from design to operation is described. Programs, requirements, specifications, and design approaches for a variety of functions (such as voice, telemetry, television, and antennas) are reviewed. Equipment environmental problems such as vibration, extreme temperature variation, and zero gravity are discussed. A review of the development of managerial techniques used in refining the roles of prime and subcontractors is included. The hardware test program is described in detail as it progressed from breadboard design to manned flight system evaluations. Finally, a series of actions is recommended to managers of similar projects to facilitate administration.

Lattier, E. E., Jr.↗

NASA NTRS1973

Technology requirements for communication satellites in the 1980's

The key technology requirements are defined for meeting the forecasted demands for communication satellite services in the 1985 to 1995 time frame. Evaluation is made of needs for services and technical and functional requirements for providing services. The future growth capabilities of the terrestrial telephone network, cable television, and satellite networks are forecasted. The impact of spacecraft technology and booster performance and costs upon communication satellite costs are analyzed. Systems analysis techniques are used to determine functional requirements and the sensitivities of technology improvements for reducing the costs of meeting requirements. Recommended development plans and funding levels are presented, as well as the possible cost saving for communications satellites in the post 1985 era.

Burtt, J. E.↗

NASA NTRS1974

Wind tunnel investigation of simulated helicopter engine exhaust interacting with windstream

A wind tunnel investigation of the windstream-engine exhaust flow interaction on a light observation helicopter model has been conducted in the Langley V/STOL tunnel. The investigation utilized flow visualization techniques to determine the cause to determine the cause of exhaust shield overheating during cruise and to find a means of eliminating the problem. Exhaust flow attachment to the exhaust shield during cruise was found to cause the overheating. Several flow-altering devices were evaluated to find a suitable way to correct the problem. A flow deflector located on the model cowling upstream of the exhaust in addition to aerodynamic shield fairings provided the best solution. Also evaluated was heat transfer concept employing pin fins to cool future exhaust hardware. The primary flow visualization technique used in the investigation was a newly developed system employing neutrally buoyant helium-filled bubbles. The resultant flow patterns were recorded on motion picture film and on television magnetic tape.

Shaw, C. S.↗

NASA NTRS1974

Automatic frequency control for FM transmitter

An automatic frequency control circuit for an FM television transmitter is described. The frequency of the transmitter is sampled during what is termed the back porch portion of the horizontal synchronizing pulse which occurs during the retrace interval, the frequency sample compared with the frequency of a reference oscillator, and a correction applied to the frequency of the transmitter during this portion of the retrace interval.

Honnell, M. A.↗

NASA NTRS1973

Holography: A survey

The development of holography and the state of the art in recording and displaying information, microscopy, motion, pictures, and television applications are discussed. In addition to optical holography, information is presented on microwave, acoustic, ultrasonic, and seismic holography. Other subjects include data processing, data storage, pattern recognition, and computer-generated holography. Diagrams of holographic installations are provided. Photographs of typical holographic applications are used to support the theoretical aspects.

Dudley, D. D.↗

NASA NTRS1974

Rotating raster generator

A rotating raster generator is provided which enables display of a television raster at any arbitrary roll angle. The generator includes four integrator circuits each of which receives a first voltage input corresponding to the sine or cosine of the desired roll angle and a second input comprising conventional horizontal or vertical sync pulses. The integrator circuits each comprise an operational amplifier and a capacitor connected for producing a ramp output having a rate of change proportional to the roll angle input, an electronic switch responsive to the sync input for resetting the integrator, and a summer that adds the ramp output of the integrator to the roll angle input so as to provide a zero-centered deflection control voltage.

Wagner, C. A.↗

NASA NTRS1973

The many faces of Mars

The Mariner Mars 1971 spacecraft was the first to orbit another planet. For 349 days, it transmitted a vast amount of data, including 7300 television pictures, gathered by its five scientific instruments. This memorandum presents some of the findings on the characteristics of the surface, atmosphere, and satellites of Mars. Included are photographs of the surface, atmosphere, satellites, surface maps, and spectrometric data for the atmosphere.

Source record↗

NASA NTRS1973

The resolution of temporal and spatial variations in auroral particle measurements from sounding rockets

The problems involved in the resolution of the temporal/spatial ambiguity in sounding rocket observations are discussed with reference to an experiment involving a mother-daughter rocket combination, together with a flashing light beacon on the rocket and television cameras on the ground. The ambiguity was successfully removed, enabling a proper interpretation of the observations of precipitating low energy electrons to be made.

Johnstone, A. D.↗

NASA NTRS1974

Values of the photometric parameters of Mars and their interpretation

Photometric data for the Martian disk obtained by Thorpe from television-camera pictures taken by Mariner 9 were used to derive values for the parameters in the photometric function. The photometric function can be applied to Mars and to the design of cameras for photography of Mars. Values of the parameters are for one wavelength only, 0.56 micros and are average or effective values for the Martian disk. The values derived were interpreted to provide semi-quantitative information on the soil. The results do not disagree with other indications that the effective mean diameter of the surface particles is about 400 micros. Another result is that the mean intercenter spacing of adjacent particles may be about 4/3 of the mean diameter.

Weaver, W. R.↗