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NASA NTRS1990

Enhanced Data-Acquisition System

Time-consuming, costly digitization of analog signals on magnetic tape eliminated. Proposed data-acquisition system provides nearly immediate access to data in incoming signals by digitizing and recording them both on magnetic tape and on optical disk. Tape and/or disk later played back to reconstruct signals in analog or digital form for analysis. Of interest in industrial and scientific applications in which necessary to digitize, store, and/or process large quantities of experimental data.

Mustain, Roy W.↗

NASA NTRS1990

Satellite radar altimetry over ice. Volume 2: Users' guide for Greenland elevation data from Seasat

A gridded surface-elevation data set and a geo-referenced data base for the Seasat radar altimeter data over Antarctica are described. It is intended to be a user's guide to accompany the data provided to data centers and other users. The grid points are on a polar stereographic projection with a nominal spacing of 20 km. The gridded elevations are derived from the elevation data in the geo-referenced data base by a weighted fitting of a surface in the neighborhood of each grid point. The gridded elevations are useful for the creating smaller-scale contour maps, and examining individual elevation measurements in specific geographic areas. Tape formats are described, and a FORTRAN program for reading the data tape is listed and provided on the tape.

Zwally, H. Jay↗

NASA NTRS1990

Satellite radar altimetry over ice. Volume 4: Users' guide for Antarctica elevation data from Seasat

A gridded surface-elevation data set and a geo-referenced data base for the Seasat radar altimeter data over Greenland are described. This is a user guide to accompany the data provided to data centers and other users. The grid points are on a polar stereographic projection with a nominal spacing of 20 km. The gridded elevations are derived from the elevation data in the geo-referenced data base by a weighted fitting of a surface in the neighborhood of each grid point. The gridded elevations are useful for the creating of large-scale contour maps, and the geo-referenced data base is useful for regridding, creating smaller-scale contour maps, and examinating individual elevation measurements in specific geographic areas. Tape formats are described, and a FORTRAN program for reading the data tape is listed and provided on the tape.

Zwally, H. Jay↗

NASA NTRS1990

SPOT 4 space magnetic recorder mechanisms

The design of the SPOT 4 satellite will be quite different from the previous ones. The design of the new magnetic tape recorder, which was derived from industrial knowledge and mission requirements; the main technical characteristics of the recorder; and the mechanical subsystems of the recorder and their locations and contributions to the final performance are all discussed. The philosophy of the development program, required to achieve the desired performance and reliability for each flight model, is described, and information on the schedule and current development is presented. The components of the tape plate system, (the transmission belts, tape rollers of the recorders, and reel hub ball bearings) which are subjected to heavy mechanical operation, fatigue, and wear in the thermal environment of the mission, are discussed. For each of the components, a description of its function in the recorder is given, as well as the mechanical stress imposed during the various operational phases. The quality testing program, which was used to verify the design safety margins, is described. Finally, the first test results of a functioning model of the flight system are presented.

Borrien, A.↗

NASA NTRS1990

Comparison of surface-derived and ISCCP cloud optical properties

One objective of the FIRE Project is to validate the cloud parameters given on ISCCP tapes. ISCCP first defines whether or not a region is clear or has clouds based on two threshold algorithms. If the region has clouds, then a cloud optical depth is given as well as a cloud height. Special high resolution ISCCP CX tapes were created for the time period of the Wisconsin FIRE experiment. These tapes did not include the cloud height product, however, other parameters used to make up the standard ISCCP Cl products were available. The ISCCP cloud/no cloud and cloud depth parameters are compared with surface derived values for the Wisconsin FIRE region during the October 27 and 28 case study days.

Whitlock, C. H.↗

NASA NTRS1990

Climate data system supports FIRE

The NASA Climate Data System (NCDS) at Goddard Space Flight Center is serving as the FIRE Central Archive, providing a centralized data holding and data cataloging service for the FIRE project. NCDS members are carrying out their responsibilities by holding all reduced observations and data analysis products submitted by individual principal investigators in the agreed upon format, by holding all satellite data sets required for FIRE, by providing copies of any of these data sets to FIRE investigators, and by producing and updating a catalog with information about the FIRE holdings. FIRE researchers were requested to provide their reduced data sets in the Standard Data Format (SDF) to the FIRE Central Archive. This standard format is proving to be of value. An improved SDF document is now available. The document provides an example from an actual FIRE SDF data set and clearly states the guidelines for formatting data in SDF. NCDS has received SDF tapes from a number of investigators. These tapes were analyzed and comments provided to the producers. One product which is now available is William J. Syrett's sodar data product from the Stratocumulus Intensive Field Observation. Sample plots from all SDF tapes submitted to the archive will be available to FSET members. Related cloud products are also available through NCDS. Entries describing the FIRE data sets are being provided for the NCDS on-line catalog. Detailed information for the Extended Time Observations is available in the general FIRE catalog entry. Separate catalog entries are being written for the Cirrus Intensive Field Observation (IFO) and for the Marine Stratocumulus IFO. Short descriptions of each FIRE data set will be installed into the NCDS Summary Catalog.

Olsen, Lola M.↗

NASA NTRS1991

Compression behavior of graphite-thermoplastic and graphite-epoxy panels with circular holes or impact damage

An experimental investigation of the compression behavior of laminated specimens made from graphite-epoxy tape, graphite-thermoplastic tape and graphite-thermoplastic fabric was conducted. Specimens with five different stacking sequences were loaded to failure in uniaxial compression. Some of the specimens had central circular holes with diameters up to 65 percent of the specimen width. Other specimens were subjected to low speed impact with impact energies up to 35 J prior to compressive loading. This investigation indicates that graphite-thermoplastic specimens with holes have up to 15 percent lower failure stresses and strains than graphite-epoxy specimens with the same stacking sequence and hole size. However, graphite-thermoplastic specimens subjected to low speed impact have up to 15 percent higher failure stresses and strains than graphite-epoxy specimens with the same stacking sequence and impact energy. Compression tests of graphite-thermoplastic specimens constructed of unidirectional tape and fabric indicate that the material form has little effect on failure strains in specimens with holes or low speed impact damage.

Jegley, Dawn C.↗

NASA NTRS1991

Organic contamination of LDEF

A brown stain of varying thickness was present on most of the exterior surface of the retrieved Long Duration Exposure Facility (LDEF). Tape lifts of Earth-end LDEF surfaces taken showed that the surface particle cleanliness immediately after retrieval was very good, but faint footprints of the tape strips on the tested surfaces indicated a very faint film was removed by the tape. Solvent wipes of these surfaces showed that the stain was not amenable to standard organic solvent removal. Infrared spectra of optical windows from tray E5 show that the organic film is hydrocarbon in composition, but is not similar to the oil that seeped from tray C12. Very dark and heavy deposits of the stain is present at openings and vents to the interior of LDEF. Heavy brown and blue-green deposits are present in the interior of LDEF where sunlight penetrated through cracks and vent openings. The exterior of LDEF had significant areas painted with a white polyurethane paint for thermal control, and almost all of the interior was painted with a black polyurethane paint. Brown staining is consistent with outgassing of hydrocarbons from these paints by rapid solar UV induced polymerization of the outgassed hydrocarbons when they hit sunlight exposed areas.

Harvey, Gale A.↗

NASA NTRS1991

A high data rate recorder for astronomy

A magnetic tape recorder developed for the special requirements of radio astronomy and geodesy is described. These requirements include a high bit packing density and long record times. The current version of this longitudinal recorder used by the Very Long Baseline Array (VLBA) records 5.5 Terabits on a 14-in diameter reel of inch-wide tape. A maximum record rate of 256 Mb/s is achieved in the VLBA configuration with one recorder operating at 4 ms and utilizing 32 of the heads in a single stack. The VLBA recorders have been tested using a longitudinal density of 2.25 fr/micron; 448 data + 56 system tracks are recorded in 14 passes, each lasting 50 min, for a total record time (at 128 Mb/s) of 12 h on 14-in diameter reel of inch-wide 13-microns-thick D1-equivalent tape.

Hinteregger, H. F.↗

NASA NTRS1992

Organic contamination of LDEF

A brown stain of varying thickness was present on most of the exterior surface of the retrieved Long Duration Exposure Facility (LDEF). Tape lifts of Earth-end LDEF surfaces taken in Feb. 1990 showed that the surface particle cleanliness immediately after retrieval was very good, but faint footprints of the tape strips on the tested surfaces indicated a very faint film was removed by the tape. Solvent wipes of these surfaces showed that the stain was not amenable to standard organic solvent removal. Infrared spectra of optical windows from tray E5 and scrapings indicate that the film is primarily of organic composition, but is not similar to the oil that seeped from tray C12. Very dark and heavy deposits of the stain are present at openings and vents to the interior of the LDEF. Heavy brown and blue-green deposits are present in the interior of LDEF where sunlight penetrated through cracks and vent openings. Photographs of the deintegrated LDEF graphically show the stain distribution. The exterior of the LDEF had significant areas painted with a white polyurethane paint for thermal control, and almost all of the interior was painted with a black polyurethane paint for thermal control. The brown staining of the LDEF is consistent with long-term outgassing of hydrocarbons from these paints followed by rapid solar-ultraviolet-induced polymerization of the outgassed hydrocarbons when the outgassed molecules stuck to surfaces exposed to sunlight.

Harvey, Gale A.↗

NASA NTRS1990

Compression behavior of graphite-epoxy and graphite-thermoplastic panels with circular holes or impact damage

An experimental investigation of the compression behavior of laminated specimens made from graphite-epoxy tape (AS4-3502), graphite-thermoplastic tape (AS4-PEEK), and graphite-thermoplastic fabric (AS4-PEEK) was conducted. Specimens with five different stacking sequences were loaded to failure in uniaxial compression. Some of the specimens had central circular holes with diameters up to 65 percent of the specimen width. Other specimens were subjected to low speed impact with impact energy up to 30 J prior to compressive loading. This investigation indicates that graphite-thermoplastic specimens with holes have up to 15 percent lower failure stresses and strains than graphite-epoxy specimens with the same stacking sequence and hole size. However, graphite-thermoplastic specimens subjected to low speed impact have up to 15 percent higher failure stresses and strains than graphite-epoxy specimens with the same stacking sequence and impact energy. Compression tests of graphite-thermoplastic specimens constructed of unidirectional tape and of fabric indicate that the material form has little effect on failure strains in specimens with holes or low speed impact damage.

Jegley, Dawn C.↗

NASA NTRS1993

Dosimeter Badge Detects Hydrazines

Disposable dosimeter badge indicates approximate cumulative exposure to hydrazine or monomethyl hydrazine in air. Indication is change in colors of both paper tapes; one coated with para-N, N-dimethylaminobenzaldehyde. Colors of exposed tapes compared with colors on two preprinted color wheels to obtain estimate of exposure. Badges help minimize risks associated with exposure of personnel to hydrazine or monomethyl hydrazine, or suspected carcinogens. Also used as stationary monitors by taping them on walls or equipment at strategic locations.

Young, Rebecca C.↗

NASA NTRS1992

Silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

A SrO-Al2O3 - 2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

Bansal, Narottam↗

NASA NTRS1992

Production of SSM/I data sets

This Final Report is a summary of the work that was performed under Contract NAS8-38075 between NASA Marshall Space Flight Center and Remote Sensing Systems from September 1989 to September 1992. The primary accomplishment was the delivery of Special Sensor Microwave/Imager (SSM/I) data tapes containing sensor and geophysical products. In all, 515 tapes (80 gigabytes) were delivered. These tapes contained the F08 SSM/I data for the period from July 1988 through December 1991 and the F10 SSM/I data for the period from December 1990 through December 1991. For the F08 SSM/I, a data inventory was compiled and an engineering assessment was done. Ephemeris tables for the F08 and F10 spacecrafts were computed. Scientific studies on the oceanic wind vector and water vapor field were published, and color atlases of monthly ocean products were produced. This investigation was part of NASA's WETNET program.

Wentz, Frank J.↗

NASA NTRS1992

Data management in NOAA

NOAA has 11 terabytes of digital data stored on 240,000 computer tapes. There are an additional 100 terabytes (TB) of geostationary satellite data stored in digital form on specially configured SONY U-Matic video tapes at the University of Wisconsin. There are over 90,000,000 non-digital form records in manuscript, film, printed, and chart form which are not easily accessible. The three NOAA Data Centers service 6,000 requests per year and publish 5,000 bulletins which are distributed to 40,000 subscribers. Seventeen CD-ROM's have been produced. Thirty thousand computer tapes containing polar satellite data are being copied to 12 inch WORM optical disks for research applications. The present annual data accumulation rate of 10 TB will grow to 30 TB in 1994 and to 100 TB by the year 2000. The present storage and distribution technologies with their attendant support systems will be overwhelmed by these increases if not improved. Increased user sophistication coupled with more precise measurement technologies will demand better quality control mechanisms, especially for those data maintained in an indefinite archive. There is optimism that the future will offer improved media technologies to accommodate the volumes of data. With the advanced technologies, storage and performance monitoring tools will be pivotal to the successful long-term management of data and information.

Callicott, William M.↗

NASA NTRS1993

Ceramic fiber reinforced glass-ceramic matrix composite

A slurry of BSAS glass powders is cast into tapes which are cut to predetermined sizes. Mats of continuous chemical vapor deposition (CVD)-SiC fibers are alternately stacked with these matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite which is heated to burn out organic constituents. The remaining interim material is then hot-pressed to form a BSAS glass-ceramic fiber-reinforced composite.

Bansal, Narottam P.↗

NASA NTRS1991

High Density Digital Data Storage System

The High Density Digital Data Storage System was designed to provide a cost effective means for storing real-time data from the field-deployable digital acoustic measurement system. However, the high density data storage system is a standalone system that could provide a storage solution for many other real time data acquisition applications. The storage system has inputs for up to 20 channels of 16-bit digital data. The high density tape recorders presently being used in the storage system are capable of storing over 5 gigabytes of data at overall transfer rates of 500 kilobytes per second. However, through the use of data compression techniques the system storage capacity and transfer rate can be doubled. Two tape recorders have been incorporated into the storage system to produce a backup tape of data in real-time. An analog output is provided for each data channel as a means of monitoring the data as it is being recorded.

Wright, Kenneth D., II↗

NASA NTRS1994

Method of producing a ceramic fiber-reinforced glass-ceramic matrix composite

A fiber-reinforced composite composed of a BaO-Al2O3-2SiO2 (BAS) glass ceramic matrix is reinforced with CVD silicon carbide continuous fibers. A slurry of BAS glass powders is prepared and celsian seeds are added during ball melting. The slurry is cast into tapes which are cut to the proper size. Continuous CVD-SiC fibers are formed into mats of the desired size. The matrix tapes and the fiber mats are alternately stacked in the proper orientation. This tape-mat stack is warm pressed to produce a 'green' composite. The 'green' composite is then heated to an elevated temperature to burn out organic constituents. The remaining interim material is then hot pressed to form a silicon carbide fiber-reinforced celsian (BAS) glass-ceramic matrix composite which may be machined to size.

Bansal, Narottam P.↗