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At least 1,423 records · Page 79
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NASA NTRS1989

Tropical squall lines of the Arizona monsoon

Three cases of squall lines composed of strong to severe thunderstorms that formed over Arizona, and Sonora (Mexico) on July, 16-17 and 17-18, 1984, and August 2-3, 1986, are examined. Data, which included satellite imagery, VISSR-derived fields, surface data, and records or cloud-to-ground lightning strikes, indicate that the initiation, growth, and dissipation of all three squall lines were very similar. Results indicate that these mesoscale convective systems developed in an environment of relatively strong low-level shear with very weak shear aloft and that they possessed almost all the properties of a typical tropical squall line.

Smith, Walter P.↗
NASA NTRS1989

High-resolution microwave images of Saturn

An analysis of high-resolution microwave images of Saturn and Saturn's individual rings is presented. Radio interferometric observations of Saturn taken at the Very Large Array in New Mexico at wavelengths of 2 and 6 centimeters reveal interesting new features in both the atmosphere and rings. The resulting maps show an increase in brightness temperature of about 3 K from equator to pole at both wavelengths, while the 6-centimeter map shows a bright band at northern midlatitudes. The data are consistent with a radiative transfer model of the atmosphere that constrains the well-mixed, fully saturated, NH3 mixing ratio to be 0.00012 in a region just below the NH3 clouds, while the observed bright band indicates a 25 percent relative decrease of NH3 in northern midlatitudes. Brightness temperatures for the classical rings are presented. Ring brightness shows a variation with azimuth and is linearly polarized at an average value of about 5 percent. The variations in ring polarization suggest that at least 20 percent of the ring brightness is the result of a single scattering process.

Grossman, A. W.↗
NASA NTRS1989

Disturbances in the Arizona Monsoon

Numerical modeling simulations of tropical squall lines were begun to determine the role of large scale terrain features over Arizona and Mexico in their initiation and propagation. Installation was completed for a short-base, high resolution lightning location and detection network in and around Tucson. Data from a Doppler wind profiler is being analyzed to determine the role of large scale heating over the inter-mountain plateau region in governing local diurnal wind variations and possible relationships to the monsoon flow. The portable solar photometer for determining high temporal resolution values of the local precipitable water vapor was completed and calibrated. The assembly is nearly completed for a multi-channel microwave passive radiometer to determine local temperature and water vapor profiles.

Gall, Robert↗
NASA NTRS1989

Contrasting landform perception with varied radar illumination geometries and at simulated resolutions of Venera and Magellan

The high sensitivity of imaging radars to slope at moderate to low incidence angles enhances the perception of linear topography on images. It reveals broad spatial patterns that are essential to landform mapping and interpretation. As radar responses are strongly directional, the ability to discriminate linear features on images varies with their orientation. Landforms that appear prominent on images where they are transverse to the illumination may be obscure to indistinguishable on images where they are parallel to it. Landform detection is also influenced by the spatial resolution in radar images. Seasat radar images of the Gran Desierto Dunes complex, Sonora, Mexico; the Appalachian Valley and Ridge Province; and accreted terranes in eastern interior Alaska were processed to simulate both Venera 15 and 16 images (1000 to 3000 km resolution) and image data expected from the Magellan mission (120 to 300 m resolution. The Gran Desierto Dunes are not discernable in the Venera simulation, whereas the higher resolution Magellan simulation shows dominant dune patterns produced from differential erosion of the rocks. The Magellan simulation also shows that fluvial processes have dominated erosion and exposure of the folds.

Ford, J. P.↗
NASA NTRS1989

GPS-aided gravimetry at 30 km altitude from a balloon-borne platform

A balloon-borne experiment, flown at 30 km altitude over New Mexico, was used to test dynamic differential Global Positioning System (GPS) tracking in support of gravimetry at high-altitudes. The experiment package contained a gravimeter (Vibrating String Accelerometer), a full complement of inertial instruments, a TI-4100 GPS receiver and a radar transponder. The flight was supported by two GPS receivers on the ground near the flight path. From the 8 hour flight, about a forty minute period was selected for analysis. Differential GPS phase measurements were used to estimate changes in position over the sample time interval, or average velocity. In addition to average velocity, differential positions and numerical averages of acceleration were obtained in three components. Gravitational acceleration was estimated by correcting for accelerations due to translational motion, ignoring all rotational effects.

Lazarewicz, Andrew R.↗
NASA NTRS1989

Performance of FFT methods in local gravity field modelling

Fast Fourier transform (FFT) methods provide a fast and efficient means of processing large amounts of gravity or geoid data in local gravity field modelling. The FFT methods, however, has a number of theoretical and practical limitations, especially the use of flat-earth approximation, and the requirements for gridded data. In spite of this the method often yields excellent results in practice when compared to other more rigorous (and computationally expensive) methods, such as least-squares collocation. The good performance of the FFT methods illustrate that the theoretical approximations are offset by the capability of taking into account more data in larger areas, especially important for geoid predictions. For best results good data gridding algorithms are essential. In practice truncated collocation approaches may be used. For large areas at high latitudes the gridding must be done using suitable map projections such as UTM, to avoid trivial errors caused by the meridian convergence. The FFT methods are compared to ground truth data in New Mexico (xi, eta from delta g), Scandinavia (N from delta g, the geoid fits to 15 cm over 2000 km), and areas of the Atlantic (delta g from satellite altimetry using Wiener filtering). In all cases the FFT methods yields results comparable or superior to other methods.

Forsberg, Rene↗
NASA NTRS1990

En route noise: NASA propfan test aircraft (corrected data - simplified procedure)

Surface noise measurements were made during a joint National Aeronautics and Space Administration (NASA) and Federal Aviation Administration (FAA) program to study the high-altitude, low-frequency acoustic noise propagation characteristics of the Advanced Turboprop (propfan) Aircraft. The measurements were made on October 26-31, 1987 in Huntsville, Alabama and on April 3-13, 1989 at the White Sands Missile Range (WSMR), New Mexico. To effectively compare flight-to-flight data as received on the ground, the procedures and practices of Federal Air Regulation (FAR) Part 36 were used as a guide in adjusting the measured ground data at the time of LA(sub MAX) to a set of reference conditions. After the data for each event were processed using slow detector characteristics, the data record at LA(sub MAX) was then identified and the coordinates of the aircraft at the time of emission were calculated, taking into account atmospheric refraction effects. The effects of atmospheric absorption through the test day and reference day atmosphere were also taken into account and the 1/3-octave data were adjusted accordingly.

Rickley, E. J.↗
NASA NTRS1990

The development of the July 1989 1 deg x 1 deg and 30' x 30' terrestrial mean free-air anomaly data bases

In June 1986 a 1 x 1 deg/mean free-air anomaly data file containing 48955 anomalies was completed. In August 1986 a 30 x 30 min mean free-air anomaly file was defined containing 31787 values. For the past three years data has been collected to upgrade these mean anomaly files. The primary emphasis was the collection of data to be used for the estimation of 30 min means anomalies in land areas. The emphasis on land areas was due to the anticipated use of 30 min anomalies derived from satellite altimeter data in the ocean areas. There were 10 data sources in the August 1986 file. Twenty-eight sources were added based on the collection of both point and mean anomalies from a number of individuals and organizations. A preliminary 30 min file was constructed from the 38 data sources. This file was used to calculate 1 x 1 deg mean anomalies. This 1 x 1 deg file was merged with a 1 x 1 deg file which was a merger of the June 1986 file plus a 1 x 1 deg file made available by DMA Aerospace Center. Certain bad 30 min anomalies were identified and deleted from the preliminary 30 min file leading to the final 30 min file (the July 1989 30 min file) with 66990 anomalies and their accuracy. These anomalies were used to again compute 1 x 1 deg anomalies which were merged with the previous June 86 DMAAC data file. The final 1 x 1 deg mean anomaly file (the July 89 1 x 1 deg data base) contained 50793 anomalies and their accuracy. The anomaly data files were significantly improved over the prior data sets in the following geographic regions: Africa, Scandinavia, Canada, United States, Mexico, Central and South America. Substantial land areas remain where there is little or no available data.

Kim, Jeong-Hee↗
NASA NTRS1990

Calibration of the visible and near-infrared channels of the LANDSAT-5 Thematic Mapper using high-altitude aircraft measurements

Visible near-infrared sensors mounted on operational satellites now in use do not have on-board full aperture absolute calibration devices. One means of establishing an in-orbit calibration for a satellite sensor is to make simultaneous measurements of a bright, uniform scene along the satellite view vector from a calibrated instrument on board a high altitude aircraft. In the work reported here, aircraft data were recorded over White Sands, New Mexico at satellite overpass time for the LANDSAT-5 Thematic Mapper (TM). A comparison of the coincident aircraft and orbiting satellite data showed the radiometric gain for TM channel 1 had degraded 4.7 percent by August 28, 1985; gains for TM channels 2 and 3 were within 1 percent of prelaunch values.

Smith, G. R.↗
NASA NTRS1989

Soil moisture and the persistence of North American drought

Numerical sensitivity experiments on the effects of soil moisture on North American summertime climate are performed using a 12-layer global atmospheric general circulation model. Consideration is given to the hypothesis that reduced soil moisture may induce and amplify warm, dry summers of midlatitude continental interiors. The simulations resemble the conditions of the summer of 1988, including an extensive drought over much of North America. It is found that a reduction in soil moisture leads to an increase in surface temperature, lower surface pressure, increased ridging aloft, and a northward shift of the jet stream. It is shown that low-level moisture advection from the Gulf of Mexico is important in the maintenance of persistent soil moisture deficits.

Oglesby, Robert J.↗
NASA NTRS1989

Infrared emission measurements of morning stratospheric N2O5

Infrared emission spectra obtained during a balloon flight of the Air Force Geophysics Laboratory Stratospheric Cryogenic Interferometer Balloon Experiment system by the University of Denver are used to measure stratospheric N2O5 after sunrise over New Mexico (latitude 33 deg N). This is the first daytime measurement of N2O5. Comparisons with photochemical modeling show consistency between the observed and predicted decline of N2O5 during the morning hours.

Blatherwick, R. D.↗
NASA NTRS1989

Lea County 001, an H5 chondrite, and Lea County 002, an ungrouped type 3 chondrite

A search of active deflation basins near Jal, Lea County, New Mexico resulted in the discovery of two meteorites, Lea County 001 and 002. Lea County 001 has mean olivine and low-Ca pyroxene compositions of Fa(19) and Fs(17), respectively. These and all other mineralogical and petrological data collected indicate a classification of H5 for this stone. Lea County 002 has mean olivine and low-Ca pyroxene compositions of Fa(2) and Fs(4), and is unequilibrated. Although it is mineralogically most similar to Kakangari and chondritic clasts within Cumberland Falls, the high modal amount of forsterite makes Lea County a unique type 3 chondrite. Oxygen isotope data for Lea County 002 fall on an 0-16-mixing line through those of the enstatite meteorites and IAB irons, a feature shared by Kakangari.

Zolensky, Michael E.↗
NASA NTRS1989

Earth observations during Space Shuttle flight STS-29 - Discovery's voyage to the earth

The environmental, geologic, meteorologic, and oceanographic phenomena documented by earth photography during the Space Shuttle STS-29 mission are reviewed. A map of the nadir point positions of earth-viewing photographs from the mission is given and color photographs of various regions are presented. The mission photographs include atmospheric dust and smoke over parts of Africa and Asia, Sahelian water sites, center pivot irrigation fields in the Middle East, urban smog over Mexico City, isolated burning in the Bolivian Amazon, and various ocean features and cloud formations.

Lulla, Kamlesh↗
NASA NTRS1990

Solar EUV irradiance derived from a sounding rocket experiment on November 10, 1988

Results are presented on the solar EUV irradiance measurements in the range 30-100 nm obtained in a sounding rocket experiment launched from the White Sands Missile Range, New Mexico, on November 10, 1988. The observed solar EUV irradiance was found to be about 20 percent less than the solar EUV flux from a proxy model based on the daily 10.7-cm solar flux and its 81-day mean and the AE-E solar EUV data taken in the 1970s. The November 10 measurement of the solar EUV flux provides a good calibration reference spectrum for the solar EUV instruments on the San Marco satellite.

Woods, Thomas N.↗
NASA NTRS1990

New instruments for solar research

In fulfilment of its goal to develop early detection and warning of emerging solar magnetic fields, the Center for Applied Solar Physics (CASP) has designed and constructed a solar vector magnetograph (VMG) that will provide unique data on the sunspot regions where flares originate. The instrument is reportedly beginning to approach its goals of measuring all three components of the solar magnetic field with a sensitivity of 50 to 100 G and a spatial resolution on the sun of about 700 km (1 arcsec). Importance of new high-resolution capabilities is stressed and the interpretation of VMG measurements is discussed. The performance of the solar VMG, installed in a 6-m dome at the National Solar Observatory at Sacramento Peak in Sunspot, New Mexico, and its construction and environment are described; particular attention is given to the use and function of the filters. Initial results are examined, including a description and analysis of a magnetogram obtained after installation of an improved blocking filter.

Rust, David M.↗
NASA NTRS1990

Regional aeolian dynamics and sand mixing in the Gran Desierto - Evidence from Landsat Thematic Mapper images

Mesoscale mapping of spatial variations in sand composition of the Gran Desierto (Sonora, Mexico) was carried out on multispectral Landsat TM images of this region, making it possible to examine the dynamic development of sand sheets and dunes. Compositions determined from remote imagery were found to agree well with samples from selected areas. The sand populations delineated were used to describe the sediment source areas, transport paths, and deposition sites. The image analysis revealed important compositional variations aver large areas that were not readily apparent in the field data.

Blount, Grady↗
NASA NTRS1991

Fourth Annual Workshop on Space Operations Applications and Research (SOAR 90)

The papers presented at the Space Operations, Applications and Research (SOAR) Symposium, hosted by the Air Force Space Technology Center and held at Albuquerque, New Mexico, on June 26-28, 1990, are documented in these proceedings. Over 150 technical papers were presented at the Symposium, which was jointly sponsored by the Air Force and NASA Johnson Space Center. the technical areas included were: Automation and Robotics, Environmental Interactions, Human Factors, Intelligent Systems, and Life Sciences. NASA and Air Force programmatic overviews and panel sessions were also held in each technical area. These proceedings, along with the comments by technical area coordinators and session chairmen, will be used by the Space Operation Technology Subcommittee (SOTS) of the Air Force Systems Command and NASA Space Technology Interdependency Group (STIG) to assess the status of the technology, as well as the joint projects/activities in various technical areas. The Symposium proceedings include papers presented by experts from NASA, the Air Force, universities, and industries in various disciplines.

Life Sciences↗
NASA NTRS1990

Rocket observations of the ultraviolet spectrum of comet Austin (1989c1)

Long slit ultraviolet spectra of Comet Austin (1989c1) were obtained from a sounding rocket experiment launched from White Sands Missile Range, New Mexico, on 21 April 1990 at 1015 UT. The instrument, known as the Faint Object Telescope, consisted of f/15.5 Dall-Kirkham telescope, a Rowland Circle spectrograph and a microchannel plate intensifier coupled to a Reticon diode array. An onboard television camera transmitted images to the ground during flight, which permitted real-time maneuvers in order to center the comet in the entrance slit. The comet was held near the center of the slit for approximately 270 seconds by sending six pointing corrections, all but one of which was less than 30 arcseconds. The comet's parameters at the time of observation, along with the characteristics of the instrument, are given.

Sahnow, D. J.↗