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At least 199 records · Page 11

ERTS-1, the spacecraft and its sensors

The basic objectives of the ERTS-1 mission are defined as follows: (1) to determine what data can be acquired from an orbiting satellite on the natural and cultural resources and on the environment; and (2) to develop and demonstrate the combination of data-acquisition procedures and interpretative techniques which can make this new knowledge available for use in the many facets of man's life. A general description of the satellite's observatory system and its sensors is given, including the thermal control subsystem, the power subsystem, the attitude control subsystem, the orbit adjust subsystem, the telemetry and tracking systems, the communications and data handling subsystem, the return beam vidicon subsystem, the multispectral scanner subsystem, the two wideband video tape recorders, and the data collection subsystem.

Weiland, S.↗

ERTS operations and data processing

The overall communications and data flow between the ERTS spacecraft and the ground stations and processing centers are generally described. Data from the multispectral scanner and the return beam vidicon are telemetered to a primary ground station where they are demodulated, processed, and recorded. The tapes are then transferred to the NASA Data Processing Facility (NDPF) at Goddard. Housekeeping data are relayed from the prime ground stations to the Operations Control Center at Goddard. Tracking data are processed at the ground stations, and the calculated parameters are transmitted by teletype to the orbit determination group at Goddard. The ERTS orbit has been designed so that the same swaths of the ground coverage pattern viewed during one 18-day coverage cycle are repeated by the swaths viewed on all subsequent cycles. The Operations Control Center is the focal point for all communications with the spacecraft. NDPF is a job-oriented facility which processes and stores all sensor data, and which disseminates large quantities of these data to users in the form of films, computer-compatible tapes, and data collection system data.

Gonzales, L.↗

LST and supporting technology

In order to realize the LST objectives of high angular resolution, extended wavelength coverage and faint object detection, the performance of the instruments must be matched to that of the telescope. To insure that adequate technology is available by 1976, an intensive SR & T program has been initiated which builds on previous work and is coordinated with work in other agencies. The primary areas of concern are detectors, on-board computers, and ultraviolet optical components. In the last area grating work is being emphasized. The on-board computer will be necessary to allow pre-processing of raw data and enable detector operation in a pulse counting mode. For detectors, the SEC Vidicon development will be continued but the use of solid-state arrays in the electron bombarded mode and channel plate detectors are being seriously considered. One challenging problem is to provide 2 K cooling to permit ultra-sensitive IR observations to be made.

Sobieski, S.↗

Optical studies of meteors at Mount Hopkins Observatory

The 10-m optical reflector and an array of phototubes are used to extend the optical measurements beyond the present limit achieved by the Vidicon system. The first detection of optical meteors with M sub v = + 12 is reported. It is hoped that this system can be used to determine intermediate points in the meteor frequency mass curve for sporadic meteors and to study in detail the faint components of meteor showers. Preliminary observations made on three nights in September 1974 are presented.

Weekes, T. C.↗

ERTS 1 flight evaluation report, 23 July 1974 to 23 October 1974

Analyses of ERTS-1 performance during the ninth quarter of its operation are presented. Topics discussed include orbital parameters, power subsystem, attitude control subsystem, command/clock subsystem, telemetry subsystem, orbit adjust subsystem, magnetic moment compensating assembly, unified S band/premodulation processor, electrical interface subsystem, thermal subsystem, narrowband tape recorders, wideband telemetry subsystem, attitude measurement sensor, wideband video tape recorders, return beam vidicon subsystem, multispectral scanner subsystem, and data collection system.

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Weather satellite picture receiving stations, APT digital scan converter

The automatic picture transmission digital scan converter is used at ground stations to convert signals received from scanning radiometers to data compatible with ground equipment designed to receive signals from vidicons aboard operational meteorological satellites. Information necessary to understand the circuit theory, functional operation, general construction and calibration of the converter is provided. Brief and detailed descriptions of each of the individual circuits are included, accompanied by a schematic diagram contained at the end of each circuit description. Listings of integral parts and testing equipment required as well as an overall wiring diagram are included. This unit will enable the user to readily accept and process weather photographs from the operational meteorological satellites.

Vermillion, C. H.↗

Integrating TV/digital data spectrograph system

A 25-mm vidicon camera was previously modified to allow operation in an integration mode for low-light-level astronomical work. The camera was then mated to a low-dispersion spectrograph for obtaining spectral information in the 400 to 750 nm range. A high speed digital video image system was utilized to digitize the analog video signal, place the information directly into computer-type memory, and record data on digital magnetic tape for permanent storage and subsequent analysis.

Duncan, B. J.↗

Development of a spectroscopic photoelectric imaging Fabry-Perot interferometer preliminary observational results

In order to observe extended astronomical objects at high spatial and spectral resolution, a spectroscopic photoelectric imaging Fabry-Perot interferometer was constructed. Among the properties chosen for the instrument are an air-spaced, piezoelectrically scanned design allowing an accurately settable free spectral range and employing a single etalon of high finesse. Careful design of the etalon mountings and optical train preserves high ligh throughput. Spectra of single spatial elements with a photomultiplier were obtained, and an SEC vidicon detector was used to record a series of images through the interferometer while scanning the wavelength in discrete steps. The latter procedure yields sufficient information to reconstruct spectral features over the entire object, and for the conditions assumed, either series of observations requires only a small fraction of a rotational period for Jupiter or Saturn. An electronic control system was also constructed which permits rapid and flexible variation of the operational mode of the Fabry-Perot and its ancilliary devices so as to minimize loss of observational time.

Smith, W. H.↗

Potential usefulness of CCD imagers in astronomy

Two dimensional detectors have been important in astronomy since the earliest days of the science. Recently, the requirements for greater photometric accuracy, sensitivity and spectral coverage have driven the search for better imaging devices. Electron beam readout devices with a variety of target materials and intensification schemes, including the SEC and silicon vidicons, have been used successfully. The CCD as an image detector has several potential advantages over electron beam readout devices; low noise, simple construction and geometric stability are among them.

Mccord, T. B.↗

Imaging on ballistic missions to comet Encke

Imaging for navigation and science has been studied for a 1980 Encke flyby at 0.4 to 0.8 AU from the sun with spinning and three-axis spacecraft. Trajectory errors, maneuvers, encounter geometry, imaging performance, and data transmission were considered. Onboard comet sightings are needed for navigation. Recommended for a three-axis spacecraft are two vidicon cameras and a nucleus sensor for closed-loop pointing control. The cameras are essentially the Mariner 9 and Mariner 10 instruments; the nucleus sensor is an updated version of a sensor flown on Mariners 6 and 7. For a spinning spacecraft, a framing camera using a charge-coupled device and a spin-scan photometer are proposed. The framing camera would be a new design; it would not be despun, but the spin axis should point along the comet-centered velocity vector. The photometer is essentially that flown on Pioneer 10 and 11.-

Jaffe, L. D.↗

Removal of instrument signature from Mariner 9 television images of Mars

The Mariner 9 spacecraft was inserted into orbit around Mars in November 1971. The two vidicon camera systems returned over 7300 digital images during orbital operations. The high volume of returned data and the scientific objectives of the Television Experiment made development of automated digital techniques for the removal of camera system-induced distortions from each returned image necessary. This paper describes the algorithms used to remove geometric and photometric distortions from the returned imagery. Enhancement processing of the final photographic products is also described.

Green, W. B.↗

Analysis and design of a surface-wave-scanned optical sensor array

This paper treats a scheme for converting the information of the spatial pattern of light of an image into a time-varying voltage pattern by the use of acoustic surface waves. After a brief review of earlier work, the application of the scheme to vidicon-type applications is tested by a feasibility calculation. This is followed by a consideration of various physical configurations possible and some experimental results. The rest of the paper deals with the subject of sensor array design. Included here are discussions of system components, methods of computation used, optimization, and the design of some integrated sensor arrays. The work shows that an integrated acoustically scanned array sensor of 250 or more elements per line in a 5 cm length, with scanning at TV frame rates, should be possible.

Shaw, K. A.↗

Mariner 10 star photography

Two identical television cameras, each having a long and short focal-length capability, were carried aboard the spacecraft for the reconnaissance of Venus and Mercury. These telescopes were used in conjunction with a filter-wheel assembly and a focal-plane shutter to provide an image on a slow-scan vidicon tube. The results obtained with this system are discussed, giving attention to aspects of sensitivity and questions related to focal length and geometric distortion.

Thorpe, T. E.↗

Orange glass - Evidence for regional deposits of pyroclastic origin on the moon

Crystallized spheres of orange glass from Shorty Crater at the Apollo 17 site are shown by spectral reflectance data to be the characteristic ingredient of the dark mantling deposit of the Taurus-Littrow region. This deposit, mapped on spectral vidicon images taken using earth-based telescopes, apparently is thickest 50 km northwest of the Apollo 17 landing area, and has a gradational contact with the surrounding materials. The irregular areal distribution of the dark-mantle deposit and the gradational borders support conclusions based on laboratory studies of the orange soils that these are volcanic pyroclastic materials. Similar deposits are identified by spectral reflectance properties near Rima Bode, Schroeter W, Fauth H, and Higinus W. The same material is likely to occur at Sulpucius Gallus based on visual and photographic observations of orange soil. The apparently restricted occurrence of the orange-glass deposits in a belt along the edges of major mare basins implies structural control of volcanic vents and a possible deep-seated origin.

Adams, J. B.↗

Low-light-level integrating video system

System consists of television camera using 25 mm SEC vidicon, low dispersion spectrograph, and digital video image system used for buffer storage of video data during tube readout scanning. Six-bit ADC converts video to digital data which are stored on magnetic tape for future evaluation.

Duncan, B. J.↗

Video simulator with electronic ranging

Gimbal orientation, raster shrinkage and deflection, and track movement are used to simulate attitude and range. Key component in system is video digitizer that converts vidicon camera signal to digital form, processes it to reduce image size, and reconverts processed data to analog signal for display on cathode ray tube.

Kraemer, W.↗

Landsat-1 and Landsat-2 evaluation report, 23 January 1975 to 23 April 1975

A description of the work accomplished with the Landsat-1 and Landsat-2 satellites during the period 23 Jan. - 23 Apr. 1975 was presented. The following information was given for each satellite: operational summary, orbital parameters, power subsystem, attitude control subsystem, command/clock subsystem, telemetry subsystem, orbit adjust subsystem, magnetic moment compensating assembly, unified S-band/premodulation processor, electrical interface subsystem, thermal subsystem, narrowband tape recorders, wideband telemetry subsystem, attitude measurement sensor, wideband video tape recorders, return beam vidicon, multispectral scanner subsystem, and data collection subsystem.

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Landsat-1 and Landsat-2 flight evaluation

The flight performance of Landsat 1 and Landsat 2 is analyzed. Flight operations of the satellites are briefly summarized. Other topics discussed include: orbital parameters; power subsystem; attitude control subsystem; command/clock subsystem; telemetry subsystem; orbit adjust subsystem; magnetic moment compensating assembly; unified s-band/premodulation processor; electrical interface subsystem; thermal subsystem; narrowband tape recorders; wideband telemetry subsystem; attitude measurement sensor; wideband video tape recorders; return beam vidicon; multispectral scanner subsystem; and data collection subsystem.

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