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At least 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

On the relative locations of the bow shocks of the terrestrial planets

The observed bow shock encounters at Mercury, Venus and Mars are least square fit using the same technique so that their sizes and shapes can be intercompared. The shock front of Mercury most resembles the terrestrial shock in shape, and the shock stand off distance is consistent with the observed moment. The shapes of the Venus and Mars shock fronts more resemble each other than the earth's and the stand off distances are consistent with direct interaction of the solar wind with the ionosphere on the dayside. The Venus shock is closer to the planet than the Mars shock suggesting more absorption of the solar wind at Venus.

Russell, C. T.↗
NASA NTRS1978

Low-speed test limit of V/STOL model located vertically off-center

A vertically off-centered V/STOL model - a 2-ft-diam three-bladed aluminum propeller operating in a rotor mode - is tested in an 8 by 12 ft wind tunnel with and without ground plane along with an associated 3 by 4.5 ft test section insert. The objective was to assess the effect of the vertically off-centered model on the low-speed test limit. The aerodynamic data of the model at a constant negative angle of attack (-3 deg) are recorded at selected tunnel dynamic pressures to provide adequate data points to define the model lift variation with respect to the tip speed ratio. The adverse effect of the rotor low-speed test limit is observed in the form of lift change with respect to the tip speed ratio. A major conclusion is that for rotors tested with a ground plane or in the vicinity of the floor, the ratio of distance between floor and model to rotor radius defines the low-speed test limits.

Shindo, S.↗
NASA NTRS1978

Io-phase motion and jovian decametre source locations

A second-order effect in the relationship between jovian decameter storms and the departure of Io from superior geocentric conjunction is explained on the basis of latitudinal variations in the earth-Jupiter viewing geometry. These variations are defined by the 12-year cycle in the jovicentric declination of the earth. In addition, it is found that the emission of the jovian decameter storm source Io-B (Io-C) is beamed from the northern (southern) magnetic latitudes. These conclusions are compatible with source positions derived from polarimetry and from considerations of planetary-limb shadowing.

Desch, M. D.↗
NASA NTRS1977

Effects of detector threshold, location of the sun, and flight altitude upon spectral variations in remote sensing over water

Photographic flights with Hasselblad cameras were flown on August 28, 1975, at altitudes from 2.66 and 5.3 kilometers over an ocean acid waste dump site while acid dumping was in progress. Repeated flights resulted in broadband spectral radiance data between the wavelengths of 500 to 900 nanometers for sun elevation angles that varied from 26 to 48 degrees, and at all sun azimuth angles over the range of off-nadir angles from 0 to 35 degrees. From film densitometer data, it is shown that before spectral variations in remotely sensed data can be used to quantify substances in water, the longer wavelength data must be above the detection level of the detector, radiance data between + or - 45 degrees in the direction of the sun must be avoided, and off-nadir camera correction factors must be applied to the observed radiance data.

Bressette, W. E.↗
NASA NTRS1978

The locations of Alpha-2 Herculis and Alpha-2 Scorpii along the line of sight

The theory of line formation along the line of sight to the visual companions of M stars undergoing spherically symmetric mass loss is developed. The theory is then used to determine the position of the companions relative to the primary. It is found that Alpha-2 Her is 1470 AU further along the line of sight than Alpha-1 Her for an adopted distance of 150 pc; Alpha-2 Sco is 420 AU closer than Alpha-1 Sco for an adopted distance of 185 pc.

Bernat, A. P.↗
NASA NTRS1978

Location of unidentified weak X-ray sources by the HEAO-1 scanning modulation collimator

Four weak sources for which precise positions have been obtained from the HEAO-1 Scanning Modulation Collimator (MC) experiment are discussed. One source (4U 0446+44) with the center of the cluster of galaxies containing 3C129 and 3C129.1 has been identified, and its angular size has been measured. One source with a galactic star is identified, although it is at galactic latitude b = 51 deg. The other two sources, 2A 0526-328 and 2A 0922-317, remain unidentified.

Schwartz, D. A.↗
NASA NTRS1978

A preliminary test of the application of the Lightning Detection and Ranging System (LDAR) as a thunderstorm warning and location device for the FHA including a correlation with updrafts, turbulence, and radar precipitation echoes

Results of a test of the use of a Lightning Detection and Ranging (LDAR) remote display in the Patrick AFB RAPCON facility are presented. Agreement between LDAR and radar precipitation echoes of the RAPCON radar was observed, as well as agreement between LDAR and pilot's visual observations of lightning flashes. A more precise comparison between LDAR and KSC based radars is achieved by the superposition of LDAR precipitation echoes. Airborne measurements of updrafts and turbulence by an armored T-28 aircraft flying through the thunderclouds are correlated with LDAR along the flight path. Calibration and measurements of the accuracy of the LDAR System are discussed, and the extended range of the system is illustrated.

Poehler, H. A.↗
NASA NTRS1979

The effect of canard relative size and vertical location on the subsonic longitudinal and lateral-directional static aerodynamic characteristics for a model with a swept forward wing

A general research fighter model was tested in the Langley 7- by 10-foot high speed tunnel at a Mach number of 0.3. The model was tested with a 32 deg swept forward wing mounted in mid-, low-, and high-wing positions. For the mid-wing configuration, the model was tested with a 51.7 deg swept back canard mounted in mid-, low-, and high-canard positions. For the mid-wing mid-canard and the mid-wing high-canard configurations, canards of similar planform having two different areas were tested. The angle-of-attack range was from approximately -4 deg to 48 deg at sideslip angles of 0 deg, -5 deg, and 5 deg.

Huffman, J. K.↗
NASA NTRS1979

The shape and location of the sector boundary surface in the inner solar system

Simultaneous observations by Helios-1 and Helios-2 over four solar rotations were used to determine the latitudinal dependence of the polarity of the interplanetary magnetic field within plus or minus 7.23 deg of the solar equator and within 1 AU. The longitudinal and latitudinal positions of the sector boundary crossing are consistent with a warped sector boundary which extended from the sun to 1 AU and was inclined approximately 10 deg with respect to the heliographic equator. This is consistent with simultaneous Pioneer 11 observations, which showed unipolar fields at latitude approximately 16 deg at heliocentric distances greater than 3.5 AU. Two sectors were observed at southern latitudes; however, four sectors were observed at northern latitudes on two rotations, indicating a distortion from planarity of the sectory boundary surface.

Villante, U.↗
NASA NTRS1978

Optimal estimation of undersea acoustic transponder locations

Using principles from multilateration and optimal estimation theories an approach is derived for estimating the relative positions of three or more submerged and anchored acoustic transponders. The procedure is not constrained to processing range data collected at special points or on special trajectories. While the data normally collected over transponders and between transponder pairs can be processed, simultaneous ranges from anywhere on the surface to three or more transponders can also be processed. Simulated examples involving four stations in different geometries with different range collection schemes demonstrate the effectiveness of the procedure.

Carta, D. G.↗
NASA NTRS1979

Location of the recurrent /LMC/ X-ray transient A0538-66 with the HEAO 1 scanning modulation collimator

Two brief (about 12 hr) X-ray flares from the direction of the Large Magellanic Cloud have been observed with the HEAO 1 scanning modulation collimator. It is argued that both originated from the recurrent fast transient A0538-66, first observed with the Ariel 5 satellite. A precise position for the source is obtained, and a B2 Iab star in the Large Magellanic Cloud is suggested as the optical counterpart. Evidence for a 16.66-day periodicity in the outburst times is presented and discussed.

Johnston, M. D.↗
NASA NTRS1978

The location of the particle acceleration region in the 1 September 1971 solar cosmic ray event

A numerical model of interplanetary propagation is used to reconstruct the shape of particle spectra near the sun shortly after release, from the proton and electron fluxes observed at 1 AU after the solar cosmic-ray event of September 1, 1971. A calculation of the spectral changes that would be produced by collisional energy losses is employed to estimate the amount of matter through which the particles passed, the height at which they were accelerated, and, for the proton, the temperature of the plasma. A temperature of about 2.4 million K in the proton acceleration region is obtained, along with a column density of material traversed equal to about 140 micrograms/sq cm for the protons and a column density of less than 4 micrograms/sq cm for the electrons. These results are shown to imply proton acceleration near the base of the corona and electron acceleration at a height greater than about 1 solar radius.

Mcguire, R. E.↗
NASA NTRS1978

An optimum PN code search technique for a given apriori signal location density

A method is presented for optimizing (minimizing) the acquisition time for a PN-type spread spectrum system when the a priori probability density function is not uniform. For an assumed a priori Gaussian density function, calculations show that the acquisition time, when the 0.5 probability acquisition time is used as a measure of acquisition time, is reduced by 40% for a cell detection probability of 0.25 and when three sweeps are used. For the same parameters and with four sweeps the acquisition time is reduced by 41%. When the acquisition time probability is set to 0.9 instead of 0.5, the reduction is 25% of the uniform sweep time.

Holmes, J. K.↗
NASA NTRS1979

The locations of X-ray sources in globular clusters

The SAS 3 X-ray observatory has been used to measure the positions of the X-ray sources in the globular clusters NGC 1851, 6441, 6624, 6712, and 7078. The derived positions have error circles with 90% confidence radii of 10 or 30 arcsec, which, in each case, include the optical center of the cluster. The results of a statistical analysis demonstrate that the X-ray sources are more concentrated toward the cluster centers than the visible stars and are therefore more massive than those stars.

Jernigan, J. G.↗
NASA NTRS1980

Low-cost calibration of acoustic locators

Method uses modified commerically-available piezoelectric-torch lighter. Handheld lighter has controlled spark gap that can be easily adjusted to produce repeatable short-duration high-amplitude voltage spikes. Pulser and lighter are coupled via short axial cable, eliminating long cable run variations in cable attenuation, and problem with cable entangling with anything in its path.

Berry, R. F.↗
NASA NTRS1979

Technique to determine location of radio sources from measurements taken on spinning spacecraft

The procedure developed to extract average source direction and average source size from spin-modulated radio astronomy data measured on the IMP-6 spacecraft is described. Because all measurements are used, rather than just finding maxima or minima in the data, the method is very sensitive, even in the presence of large amounts of noise. The technique is applicable to all experiments with directivity characteristics. It is suitable for onboard processing on satellites to reduce the data flow to Earth. The application to spin-modulated nonpolarized radio astronomy data is made and includes the effects of noise, background, and second source interference. The analysis was tested with computer simulated data and the results agree with analytic predictions. Applications of this method with IMP-6 radio data have led to: (1) determination of source positions of traveling solar radio bursts at large distances from the Sun; (2) mapping of magnetospheric radio emissions by radio triangulation; and (3) detection of low frequency radio emissions from Jupiter and Saturn.

Fainberg, J.↗