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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Use of ERTS-1 data: Summary report of work on ten tasks

The author has identified the following significant results. Depth mapping's for a portion of Lake Michigan and at the Little Bahama Bank test site have been verified by use of navigation charts and on-site visits. A thirteen category recognition map of Yellowstone Park has been prepared. Model calculation of atmospheric effects for various altitudes have been prepared. Radar, SLAR, and ERTS-1 data for flooded areas of Monroe County, Michigan are being studied. Water bodies can be reliably recognized and mapped using maximum likelihood processing of ERTS-1 digital data. Wetland mapping has been accomplished by slicing of single band and/or ratio processing of two bands for a single observation date. Both analog and digital processing have been used to map the Lake Ontario basin using ERTS-1 data. Operating characteristic curves were developed for the proportion estimation algorithm to determine its performance in the measurement of surface water area. The signal in band MSS-5 was related to sediment content of waters by modelling approach and by relating surface measurements of water to processed ERTS data. Radiance anomalies in ERTS-1 data could be associated with the presence of oil on water in San Francisco Bay, but the anomalies were of the same order as those caused by variations in sediment concentration and tidal flushing.

Thomson, F. J.↗
NASA NTRS1974

A study of the utilization of ERTS-1 data from the Wabash River Basin

The author has identified the following significant results. The most significant results were obtained in the water resources research, urban land use mapping, and soil association mapping projects. ERTS-1 data was used to classify water bodies to determine acreages and high agreement was obtained with USGS figures. Quantitative evaluation was achieved of urban land use classifications from ERTS-1 data and an overall test accuracy of 90.3% was observed. ERTS-1 data classifications of soil test sites were compared with soil association maps scaled to match the computer produced map and good agreement was observed. In some cases the ERTS-1 results proved to be more accurate than the soil association map.

Landgrebe, D. A.↗
NASA NTRS1974

Comparison of ERTS-1 and Skylab-EREP for interdisciplinary coastal investigations

The author has identified the following significant results. NASA's ERTS-1 satellite and Skylab EREP have both provided imagery suitable for investigating coastal vegetation, land use, current circulation, water turbidity, waste disposal, and sea state. Based on high contrast targets, such as piers and breakwaters, the ERTS-1 MSS seems to have a resolution of 70-100 meters, Skylab's S190A about 30-70 meters, and its S190B about 10-30 meters. Important coastal land use details can be more readily mapped using Skylab's imagery. On the other hand, the regular eighteen day cycle of ERTS-1 allows observation of important manmade and natural changes, and facilitates collection of ground truth. The Skylab/EREP multispectral scanner offers 13 spectral bands as compared to 4 bands on ERTS-1. However, EREP scanner tapes require special filtering to remove several types of noise and their conical line scan pattern must be linearized before one can identify small targets based on spatial features.

Klemas, V.↗
NASA NTRS1973

Multispectral combination and display of ERTS-1 data

A significant problem in the use of ERTS-1 data is the extraction of information pertinent to each application and the presentation of that information in a form most suitable to users. When the information is to be displayed for visual study by an observer, the problem can be reduced to two steps: (1) Dimensionality reduction, an objective procedure which attempts to preserve most of the ERTS-1 information in a smaller number of components. (2) Display of the reduced number of components for optimum visibility by an observer. A specific dimensionality reduction technique has been applied to ERTS-1 data for several geographical areas in California and distinct types of earth resources. In the display of the reduced number of components, consideration has to be given to properties of the human visual system and the statistics of the data to be displayed. Previous work on digital image enhancement was applied to this problem to generate color composites which contain and display most of the information provided by the ERTS-1 sensors. Results of this approach were interesting, both in terms of the small mean-square caused by the dimensionality reduction, as well as for the examples of enhanced images that have been obtained.

Algazi, V. R.↗
NASA NTRS1974

Study of low frequency hydromagnetic waves using ATS-1 data

An analysis was made of ATS-1 data to determine at what point in the magnetic storm recovery phase are oscillations most likely to begin. The catalog of hourly values of equatorial Dst was used to determine the time of main phase decrease, and a catalog of oscillations from January to May 1968 to determine onset time as observed by ATS-1. For each oscillation event at ATS-1, the nearest prior main phase decrease with a magnitude of at least -35 gamma was determined, and the time difference between the onset of the event at ATS-1 and the time of main phase decrease was measured. The resulting data indicate that the most probable time to observe onset of transverse oscillations is within 24 hours after the main phase decrease.

Cummings, W. D.↗
NASA NTRS1974

Monitoring the dispersion of ocean waste disposal plumes from ERTS-1 and Skylab

The author has identified the following significant results. About forty miles off the Delaware coast is located the disposal site for waste discharged from a plant processing titanium dioxide. The discharge is a greenish-brown; 15-20% acid liquid which consists primarily of iron chlorides and sulfates. The barge which transports this waste has a 1,000,000 gallon capacity and makes approximately three trips to the disposal site per week. ERTS-1 MSS digital tapes are being used to study the dispersion patterns and drift velocities of the iron-acid plume. Careful examination of ERTS-1 imagery disclosed a fishhook-shaped plume about 40 miles east of Cape Henlopen caused by a barge disposing acid wastes. The plume shows up more strongly in the green band than in the red band. Since some acids have a strong green component during dumping and turn slowly more brownish-reddish with age, the ratio of radiance signatures between the green and red bands may give an indication of how long before the satellite overpass the acid was dumped. Enlarged enhancements of the acid waste plumes, prepared from the ERTS-1 MSS digital tapes aided considerably in studies of the dispersion of the waste plume. Currently acid dumps are being coordinated with ERTS-1 overpasses.

Klemas, V.↗
NASA NTRS1974

Observations of Circinus X-1 from Uhuru

Analysis of Uhuru observations of the X-ray source Cir X-1 (3U 1516-56) suggests that the source may be a binary with a period longer than 15.0 days. Significant intensity variations have been observed on all time scales from 0.1 sec to days. Changes in the X-ray energy spectrum from 2 to 20 keV have also been found. A refined X-ray position, containing no obvious optical counterpart, is reported. The similarities between Cyg X-1 and Cir X-1 suggest that the X rays from Cir X-1 may be produced by accretion onto a massive, collapsed object.

Jones, C.↗
NASA NTRS1978

Rolling-element fatigue life of AISI M-50 and 18-4-1 balls

Rolling element fatigue studies were conducted with AISI M-50, EFR 18-4-1, and VAR 18-4-1. Groups of 12.7 mm (1/2-in) diameter balls of each material were tested in the five ball fatigue tester. Test conditions included a load of 1540 N (347 lbf) giving a maximum Hertz stress of 5520 MPa (800 000 psi), a shaft speed of 10,700 rpm, and a contact angle of 30 deg. Tests were run at a race temperature of 339 K (150 F) with a type 2 ester lubricant. The rolling element fatigue life of AISI M-50 was not significantly different from that of EFR 18-4-1 or VAR 18-4-1 based on a statistical comparison of the test results.

Parker, R. J.↗
NASA NTRS1979

Strain compatibility assessment for SRB sprayable ablator MSA-1

Tensile and compressive strain compatibility testing was performed on as-sprayed samples of the Shuttle Solid Rocket Booster external ablator material, MSA-1. Strain gages on the aluminum substrate were used to monitor strain. Strain compatibility was determined as the percent strain in the substrate at first visual evidence of MSA-1 failure. The 1/8-in. MSA-1, baselined for large areas of the SRB external skin, was characterized by a strain compatibility of 1.5 to 1.8 percent, which far exceeded the yield range of the metal substrate. Thicker MSA-1 applications (1.4 to 3/8 in.) were characterized by a lower level of strain compatibility, which appeared to be a manifestation of application limitations.

Patterson, W. J.↗
NASA NTRS1979

Extended-bandwidth X-ray observations of Cygnus X-1

An energy- and time-resolved observation of Cyg X-1, sensitive from 0.15 to 20 keV, is reported which was performed to investigate the spectrum and time variability of the flux at low X-ray energies. Data in the band from 1.5 to 42 keV, obtained in two previous rocket flights, are reanalyzed to search for any energy dependence of the time signature. No such energy dependence is found, so the explanation of the observed low-energy excess of Cyg X-1 as emission from an extended region separate from the high-energy source is rendered untenable. The evident stability of the power-law spectrum of Cyg X-1 through the observed shot-noise variation is shown to suggest that the spectrum has a Comptonization origin. It is concluded that there is no obvious analogy to be made between Cyg X-1 and X-ray bursters.

Priedhorsky, W.↗
NASA NTRS1981

Rapid X-ray and optical flares from Scorpius X-1

A 1 second time structure in X-ray flares from Sco X-1 and simultaneous optical flares with time structures no faster than 20 s are reported. The shortest reported time scale in the X-ray emission from Sco X-1 is decreased by a factor of 10, while remaining consistent with the parameters of the standard plasma model from Sco X-1. Different mechanisms for the production of X-ray flares and optical flares are suggested, and the production of optical flares by reprocessing on the surface of the binary companion of Sco X-1 is ruled out by the X-ray/optical flare time delay.

Petro, L. D.↗
NASA NTRS1983

VLBI observations of a radio flare of Circinus X-1

VLBI 2.3 GHz observations of a strong radio flare of the binary star system Circinus X-1 indicate a radio source flaring component angular size of 0.0015-0.015 arcsec. This is equivalent to a linear size of 15-150 AU at the 10 kpc distance of Circinus X-1, although interstellar medium scattering may have enlarged the apparent angular source size. Since the radio source quiescent component, observed prior to the flare, had an angular size greater than 0.2 arcsec (equivalent to more than 2000 AU at 10 kpc), the quiescent radio emission comes from a region much larger than that proposed in recent models for Circinus X-1. The quiescent component appears to be variable on a time scale of years, and is probably fueled by the Circinus X-1 binary system.

Preston, R. A.↗
NASA NTRS1983

X-ray observations of LMC X-3 with the monitor proportional counter aboard the HEAO 2 Einstein observatory - A comparison with Cygnus X-1

A comparison is presented of the black hole candidates LMC X-3 and Cygnus X-1 based on Einstein observations of LMC X-3 with the monitor proportional counter. A spectral analysis shows LMC X-3 to be more like the typical bright galactic X-ray source than Cygnus X-1. A search for periodic pulsations over a period range from 0.2 ms to over 1000 s set upper limits at the 90 percent confidence level of the order of 10 percent. An analysis of the aperiodic variability of LMC X-3 shows none of the shot noise behavior characteristic of Cygnus X-1. The absence of distinctive X-ray properties common to both sources suggests that the identification of black hole candidates on the basis of X-ray properties similar to Cygnus X-1 (or LMC X-3) is not reliable.

Weisskopf, M. C.↗
NASA NTRS1984

SMC X-1 variability observed from HEAO 1

Studies are reported of the slow variability of SMC X-1 and its spectrum. An analysis of red-noise random variability is based on a method discussed by Deeter and Boynton (1982). The 0.7 s X-ray pulsar SMC X-1 is in a 3.89 day eclipsing binary system with a B0 I supergiant companion. Observations of the pulsar were conducted with the aid of the UCSD/MIT instrument on HEAO 1 from 1977 August through 1979 January. A light curve was constructed for the period 1977 September to 1978 December. The apparent tendency of SMC X-1 to be in one of two states, high or low, suggests the acquisition of average spectra separately for each state. The total (steady plus pulsed) emission from SMC X-1 displays a continuum spectrum with a dominant exponential form which implies a temperature of 17 keV for thin thermal bremsstrahlung emission or 5 keV if the other limit of a Wien spectrum is assumed.

Gruber, D. E.↗
NASA NTRS1985

Detection of a compact companion of the mild barium star Xi-1 Ceti

In the present paper, the observation of a white dwarf companion of the mild Ba star Xi-1 Ceti (= 65 Ceti = HR 649 = HD 13611) is reported, taking into account also the properties of the mild Ba star and of its companion. The UV spectrum of Xi-1 Ceti is discussed along with an interpretation of this spectrum. Attention is given to the effective temperature of the companion, the absorption bands in the spectrum, the radius and mass of the Xi-1 Ceti companion, and questions regarding the obscuration of the companion by the atmosphere of the Ba star. It is found that the overall energy distribution of the Xi-1 Ceti companion can best be matched with a 14,000 K DA white dwarf of log g = 8 or less. However, the absolute intensity is too small and would require a radius too small and a mass too large for such a gravity.

Bohm-Vitense, E.↗
NASA NTRS1985

Response of the middle atmosphere to Sco X-1

On the night of Mar. 9, 1983 (UT) at Punta Lobos Launch Site, Peru (12.5 deg S, 76.8 deg W, magnetic dip -0.7 deg), a sequence of sounding rockets was flown to study the electrical structure of the equatorial middle atmosphere and to evaluate perturbations on this environment induced by the X-ray star Sco X-1. The rocket series was anchored by two Nike Orion payloads (31.032 and 31.033) which were launched at 0327 and 0857 UT, near Sco X-1 star-rise and after it had attained an elevation angle of 70 deg E. An enhanced flux of X-rays was observed on the second Nike Orion flight (31.033). This increase is directly attributed to Sco X-1, both from the spectral properties of the measured X-ray distribution and by spatial information acquired from a spinning X-ray detector during the upleg portion of the 31.033 flight. Simultaneously, a growth in ion conductivity and density was seen to occur in the lower mesosphere between 60 and 80 km on the second flight, specifically in the region of maximum energy deposition by the Sco X-1 X-rays. The results imply the presence of a significant number of ionized heavy constituents within the lower mesosphere, with masses possibly in the submacroscopoic range.

Goldberg, R. A.↗
NASA NTRS1986

Ultraviolet spectrum and probable chemical composition of the high-excitation planetary nebula M1-1

Data obtained with the IUE and with the image-tube scanner on the Shane 3-m telescope at the Lick Observatory were used to determine the possible chemical composition of the high excitation nebula, M1-1. Though N may be enhanced, the composition of M1-1 does not seem to differ significantly from that of the sun, in contrast to NGC 6537. M1-1 abundances do not appear to differ by more than about a factor of two from those of the mean planetaries or the sun. NGC 6537 and NGC 6302 show large effects of nuclear processing in C, N, and possibly O, while M1-1, in spite of its high excitation and presumed origin from a relatively massive star, shows insignificant effects of nuclear processing.

Aller, L. H.↗
NASA NTRS1986

ERS-1 SAR data processing

To take full advantage of the synthetic aperature radar (SAR) to be flown on board the European Space Agency's Remote Sensing Satellite (ERS-1) (1989) and the Canadian Radarsat (1990), the implementation of a receiving station in Alaska is being studied to gather and process SAR data pertaining in particular to regions within the station's range of reception. The current SAR data processing requirement is estimated to be on the order of 5 minutes per day. The Interim Digital Sar Processor (IDP) which was under continual development through Seasat (1978) and SIR-B (1984) can process slightly more than 2 minutes of ERS-1 data per day. On the other hand, the Advanced Digital SAR Processore (ADSP), currently under development for the Shuttle Imaging Radar C (SIR-C, 1988) and the Venus Radar Mapper, (VMR, 1988), is capable of processing ERS-1 SAR data at a real time rate. To better suit the anticipated ERS-1 SAR data processing requirement, both a modified IDP and an ADSP derivative are being examined. For the modified IDP, a pipelined architecture is proposed for the mini-computer plus array processor arrangement to improve throughout. For the ADSP derivative, a simplified version is proposed to enhance ease of implementation and maintainability while maintaing real time throughput rates. These processing systems are discussed and evaluated.

Leung, K.↗