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At least 325 records · Page 18

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NASA NTRS1973

Crater frequency age determinations for the proposed Apollo 17 site at Taurus-Littrow.

On the assumption that the vast majority of craters are of impact origin, relative age dates can be obtained by counting craters. Returned lunar samples are helping to resolve problems regarding the magnitude of the meteoritic flux. The samples provide a means for empirically calibrating crater count data. The characteristics of the Taurus-Littrow area are considered, giving attention to four different units. The crater frequency distribution is discussed, together with its significance for the age of the corresponding lunar features.

Greeley, R.↗

NASA NTRS1973

Development of a global cloud model for simulating earth-viewing space missions.

Existing global cloud models are improved and expanded so that they might be more effectively used in planning and evaluating potential earth-viewing space missions. A relationship is developed between the ground and satellite-derived cloud-amount frequency distributions. This relationship is used to improve internal consistency between the ground-observed unconditional statistics and the satellite-derived conditional statistics as tabulated in previous models. A statistical technique is developed which permits the scaling of the conditional statistics to time and distance separations other than those for which the data base is tabulated. A new technique to increase or decrease the representative area size of the statistical data base is developed. Both the scaling and area adjustment techniques are shown to represent significant improvements over the techniques previously employed.

Greaves, J. R.↗

NASA NTRS1973

Calibration of radar data from Apollo 17 and other mission results

An examination was made of radar data on depolarized radar echoes for the general areas of (1) the Apollo 11, 12, 14, 15, 16, and 17 landing sites, (2) Ranger 7, 8, and 9 impact sites, and (3) the Surveyor 1, 3, 5, and 7 landing sites. These data were then compared with photographic data. Surveyor 6 was excluded because it landed near the center of the lunar disk where echo data are poor. Three problems concerning the echo data are (1) the frequency distributions of echo strengths from site to site, (2) the areal distribution of echoes, and (3) detailed correlation of echoes with the photographs of the Apollo 17 landing area.

Moore, H. J.↗

NASA NTRS1973

Dielectric spectra of Apollo 15 and 16 lunar solid samples

Description of the dielectric constants, losses, and ac-conductivities of lunar samples 15065,27, 15459,62, 15555,88, 15415,57, 60015,29, 60315,34, 61016,34, and 62235,17 as measured over a range of frequencies from 100 Hz to 10 MHz and temperatures from 77 to 473 K by two-terminal capacitance substitution methods. The dielectric spectra of lunar gabbroic basalts are typified by the dielectric behavior of samples 15065 and 15555, showing complex relaxation processes which are both frequency- and temperature-dependent. Such feldspar-rich crystalline lunar basalts like samples 15459, 62235, and 60015 showed essentially the same dielectric relaxation mechanisms which are also a function of both frequency and temperature with a very broad relaxation frequency distribution. Highly-brecciated lunar sample, 60315, exhibits rather an unusual dielectric behavior which is dependent upon on field-strength.

Chung, D. H.↗

NASA NTRS1973

The ATS-F radio frequency interference measurement experiment

The technical objectives of the uplink interference tests and measurements to be performed during this experiment are set forth as the determination of the integrated interference power from all 6-GHz terrestrial sources sharing the common carrier band with the RF field of view of the ATS-F satellite; the establishment of practical limits of receiver antenna gain-to-noise temperature ratios for satellites sharing the common 6-GHz carrier band; and the determination of the geographical and frequency distribution of 6-GHz terrestrial sources sharing the common carrier band. A brief description of the RF interference measurement system with some details on its hardware and subsystems is included. The performance characteristics of the mission and a measurement program are discussed.

Henry, V. F.↗

NASA NTRS1974

Electrical properties of lunar soil sample 15301,38

Electrical property measurements have been made on an Apollo 15 lunar soil sample in ultrahigh vacuum from room temperature to 827 C for the frequency spectrum from 100 Hz through 1 MHz. The dielectric constant, the total ac loss tangent, and the dc conductivity were measured. The dc conductivity showed no thermal hysteresis, but an irreversible (in vacuum) thermal effect was found in the dielectric loss tangent on heating above 700 C and during the subsequent cooling. This appears to be related to several effects associated with lunar glass above 700 C. The sample also showed characteristic low-frequency dispersion in the dielectric constant with increasing temperature, presumably due to Maxwell-Wagner intergranular effects. The dielectric properties may be fitted to a model involving a Cole-Cole frequency distribution that is relatively temperature-independent below 200 C and follows a Boltzmann temperature distribution with an activation energy of 2.5 eV above 200 C. The dc conductivity is fitted by an exponential temperature distribution and becomes the dominant loss above 700 C.

Olhoeft, G. R.↗

NASA NTRS1974

Cluster analysis based on dimensional information with applications to feature selection and classification

A new clustering algorithm is presented that is based on dimensional information. The algorithm includes an inherent feature selection criterion, which is discussed. Further, a heuristic method for choosing the proper number of intervals for a frequency distribution histogram, a feature necessary for the algorithm, is presented. The algorithm, although usable as a stand-alone clustering technique, is then utilized as a global approximator. Local clustering techniques and configuration of a global-local scheme are discussed, and finally the complete global-local and feature selector configuration is shown in application to a real-time adaptive classification scheme for the analysis of remote sensed multispectral scanner data.

Eigen, D. J.↗

NASA NTRS1974

Martian cratering and central peak statistics - Mariner 9 results

Mariner 9 imagery shows that central peaked craters occur much more frequently in the Martian south polar region than in typical equatorial areas, and that both regions have crater size frequency distributions characteristic of saturation. Several arguments indicate that a preferential production mechanism, e.g., pingo formation made possible by subsurface permafrost confined to Martian polar regions, may account for the central peak excess in the south polar region.

Cordell, B. M.↗

NASA NTRS1974

Comparison of five levels of motion sickness severity as the basis for grading susceptibility

The motion sickness susceptibility of 275 healthy male subjects was measured quantitatively by a standardized laboratory procedure using a Stille rotational chair. The results, in terms of velocity of the chair and the number of active head movements, were combined into a single numerical score that represented the total stressor stimulus sustained in reaching, in turn, each of five specific criteria for diagnosing the severity of motion sickness. The stressor value (E factor) of a single head movement at each test rpm was adjusted to yield an equivalent susceptibility score (Coriolis Sickness Susceptibility Index, or CSSI) independent of the endpoint selected. Close agreement among the CSSI scores obtained at each endpoint was found in intercorrelations, test-retest reliability coefficients, and frequency distributions, which reflected the orderliness and stability in the appearance, ramification, and intensification of the acute symptomatology evoked in progressing from mild malaise to frank sickness.

Miller, E. F., II↗

NASA NTRS1974

Evidence for an episode of crater obliteration intermediate in Martian history

It is shown that Mars experienced a brief episode of an increased obliteration rate contemporaneous with the formation of the cratered plains units. The obliteration rate during this episode was at least an order of magnitude greater than the preexisting rate. The obliteration rates prior to and after the event were identical within a factor of 3. Regional variations in the observed densities of degraded craters on the cratered terrain are shown to result from differences in the intensity of the obliteration rate during the event. The identification and characterization of the event are accomplished by using crater diameter-frequency distributions, not only for the total crater population but also for four morphological classes. Distributions are selected from 38 regions within the Martian equatorial latitudes.

Jones, K. L.↗

NASA NTRS1974

The micrometeoroid complex and evolution of the lunar regolith

The interaction of the micrometeoroid complex with the lunar surface is evidenced by numerous glass-lined microcraters on virtually every lunar surface exposed to space. Such craters range in size from less than .1 micron to approximately 2 sq cm diameter. Using small scale laboratory cratering experiments for calibration, the observed crater-sized frequency distributions may be converted into micrometeoroid mass distributions. These lunar mass distributions are in essential agreement with satellite data. Some physical properties of micrometeoroids may be deduced by comparing lunar crater geometries with those obtained in laboratory experiments. The proponderance of circular outlines of lunar microcraters necessitates equidimensional, if not spherical, micrometeoroids.

Hoerz, F.↗

NASA NTRS1974

Estimations of the smoothing operator response characteristics

The mean response characteristic of the graphical smoothing method is discussed. The method is illustrated by analysis of latitude observations at Washington from 1915.9 to 1941.0. Spectral density, frequency distribution, and distribution functions are also discussed.

Yatskiv, Y. S.↗

NASA NTRS1975

Relation of lineaments to sulfide deposits: Bald Eagle Mountain, Centre County, Pennsylvania

The author has identified the following significant results. Discrete areas of finely-fractured and brecciated sandstone float are present along the crest of Bald Mountain and are commonly sites of sulfide mineralization, as evidenced by the presence of barite and limonite gossans. The frequency distributions of the brecciated float as the negative binomial distribution supports the interpretation of a separate population of intensely fractured material. Such zones of concentrated breccia float have an average width of one kilometer with a range from 0.4 to 1.6 kilometers and were observed in a quarry face to have subvertical dips. Direct spatial correlation of the Landsat-derived lineaments to the fractured areas on the ridge is low; however, the mineralized and fracture zones are commonly assymetrical to the lineament positions. Such a systematic dislocation might result from an inherent bias in the float population or could be the product of the relative erosional resistance of the silicified material in the mineralized areas in relation to the erosionally weak material at the stream gaps.

Mcmurtry, G. J.↗

NASA NTRS1974

Minor planets and related objects. XVI - Polarimetric diameters

Polarimetric observations of 43 asteroids are presented. All objects show a well-developed negative polarization branch as an indicator of unconsolidated surface regoliths. The empirical slope-albedo law for diffusely reflecting solid surfaces is reexamined and used to compute polarimetric albedos and diameters for 30 asteroids. In many cases the results are in good agreement with infrared-radiometric diameters; the older visual diameter measurements were systematically too small. Radiometric albedos below 5%, however, are not confirmed by the polarimetry. Bimodal frequency distributions are noted for asteroid color, albedo, and the depth of the negative polarization branch. Correlations between B - V color and polarimetric parameters suggest that most of the asteroid population can be divided into silicaceous and carbonaceous opacity classes.

Zellner, B.↗

NASA NTRS1974

Micrometeoroids and lunar rocks

Description of present concepts of the lunar micrometeoroid flux as deduced from microcrater observations on lunar rocks and available laboratory simulations with smooth glassy surfaces. Results examined include factors governing microcrater morphology, size frequency distribution, and correlation of lunar rock surface exposure ages with absolute crater number densities.

Hoerz, F.↗

NASA NTRS1974

Aerosols at 20 kilometers altitude

Stratospheric aerosols were collected at the 20 km altitude zone by direct impaction on 0.2mm palladium wires in view of the previously observed minimum in particle size frequency distribution between 0.1 and 0.2 microns. Since no minimum in size distribution around 0.2 microns was found, it is concluded that previous equipment was inefficient in collection in this range. Concentration results suggest that low particle concentrations result from small particles agglomerating to form larger ones. Since no indentations were found on the wires used in this experiment, and since there were no differences in the number of particles found on oil-coated surfaces vs uncoated surfaces, the particles in the stratosphere must be liquid, liquid coated, or a slurry.

Ferry, G. V.↗

NASA NTRS1975

Thresholds for the perception of angular acceleration as indicated by the oculogyral illusion

A motorized chair (with precise servo controls) accelerated the observer in a clockwise (CW) or counterclockwise (CCW) direction at rates that ranged in logarithmic progression from 0.02 to 6.00 deg/sq sec. The target, a narrow collimated line of light, was contained within a goggle device worn by the observer and therefore fixed in relative position to him. The illusion, appearing as rightward or leftward movement of the visual target in the direction of acceleration, was determined by a double staircase procedure among 300 normal and 4 labyrinthine-defective observers. None of the latter perceived the illusion. The majority of normal observers revealed no substantial directional difference (CW vs. CCW threshold). Threshold frequency distributions ranged in rate (deg/sq sec) from 0.020 to 0.950; the threshold of response in more than half the normal observers was less than 0.10, in over three-fourths was less than 0.20, in over 90% less than 0.30, and 100% less than 1.00.

Miller, E. F., II↗

NASA NTRS1974

Meteorological variables versus CAT in the stratosphere - A statistical approach

Frequency distributions prepared from synoptic meteorological parameters at 300, 200, and 100 mb, associated with turbulent and non-turbulent areas encountered by the XB-70 airplane in the stratosphere (between 12 and 20 km), show that turbulence occurs more frequently than non-turbulence when the parameters exceed certain values. A procedure proposed for forecasting clear-air turbulence on the basis of the number of exceedances of limits of specified variables is verified for two flights of the XB-70 airplane. The procedure gives the geographical location of CAT regions, but further research is required before the altitude of CAT can be specified.

Scoggins, J. R.↗