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This presentation is a set of charts presented at the 2024 AIAA ASCEND conference. This report is the result of an activity sponsored by Dr. Wanda Peters, Deputy Associate Administrator of Programs, who tasked Florence Tan and Carolyn Mercer with gathering insights from SmallSat/ Class D missions that could be extrapolated to enhance Class A-C missions.
This report accompanies is a set of charts that will be presented at the 2024 LEARN Forum. This report is the result of an activity sponsored by Dr. Wanda Peters, Deputy Associate Administrator of Programs, who tasked Florence Tan and Carolyn Mercer with gathering insights from SmallSat/ Class D missions that could be extrapolated to enhance Class A-C missions.
A graphic method of analyzing radar scatterometer sea clutter data leading to linear relations between scattering cross sections and tan angle of incidence of the radiation is proposed. This relation permits formulation of simple analytic relations without reference to the ocean surface spectrum. Parameters introduced depend on the wavelength of the incident radiation and its polarization, and on wind and sea states. The simplicity of the expressions derived suggests a corresponding simplicity in the physical mechanism of radar sea clutter return.
Approximations which can be evaluated with precision using floating-point arithmetic are presented. The particular set of approximations thus far developed are for the function TAN and the functions of USASI FORTRAN excepting SQRT and EXPONENTIATION. These approximations are, furthermore, specialized to particular forms which are especially suited to a computer with a small memory, in that all of the approximations can share one general purpose subroutine for the evaluation of a polynomial in the square of the working argument.
It was concluded that the Surveyor 3 spacecraft moved, probably as a result of a sudden failure of the leg 3 shock absorber, between May 1967 and November 1969. The time at which the movement occurred can be estimated only from comparison of the shielded and unshielded portions of footpad 3 and a knowledge of the mechanism and rate of the process that tans the painted surface.
Cerment materials (HfC - 10 wt% W; HfC - 10 wt% TaC - 10 wt%W; HfC - 2 wt% CbC - 8 wt% Mo;Hfn - 10 wt% W; Hfn - 10 wt% TaN - 10 wt% W; and ZrC - 17 wt% W) were evaluated for possible use as lithium-lubricated bearings in the control system of a nuclear reactor. Tests of compatibility with lithium were made in T-111 (Ta-8W-2Hf) capsules at temperatures up to 1090 C. The tendencies of HfC-TaC-W, HfC-CbC-Mo, and HfN-W to bond to themselves and to the refractory alloys T-111 and TZM when enclosed in lithium-filled capsules under a pressure of 2000 psi at 980 and 1200 C for 1933 hours were evaluated. Thermal expansion characteristics were determined for the same three materials from room temperature to 1200 C. On the basis of these tests, HfC-10 TaC-10W and HfN-10W were selected as the best and second best candidates, respectively, of the materials tested for the bearing application.
The Apollo 17 astronauts removed four rocks samples to represent each of the lithologies they recognized in the boulder at station 7: sample 77215 from an off-white meter-sized block; sample 77075 from one of the thin dikes that cross the off-white block; 77115 from the blue-gray rock adjacent to the off-white block and apparently continuous with thin dikes that cross the block; sample 77135 of the tan-gray or green-gray vesicular rock adjacent to the blue-gray (77115) rock. A consortium of investigators has been organized to study the samples. Each sample shows a number of lithologic types in terms of clasts (or xenoliths) and matrices. A table shows how subsamples have been allocated for consortium study. Maps and photographs show the relations between subsample locations and lithologies for the two more dissected samples, 77115 and 77135.
The author has identified the following significant results. Preliminary analysis indicates that mineralogical differences between altered rocks and most unaltered rocks in south-central Nevada cause visible and near infrared spectral reflectance differences, which can be used to discriminate these broad categories of rocks in multispectral images. The most important mineralogical differences are the increased abundance of goethite, hematite, and jarosite, and the presence of alunite, montmorillonite, and kaolinite in the altered rock. The technique to enhance subtle spectral differences combines ratioing of the MSS bands and contrast stretching. The stretched ratio values are used to produce black and white images that depict materials according to spectral reflectance; rationing minimizes the influence of topography and overall albedo on the grouping of spectrally similar materials. Field evaluation of color-ratio composite shows that, excluding alluvial areas, approximately 80 percent of the green and brown color patterns are related to hydrothermal alternation. The remaining 20 percent consists mainly of pink hematitic crystallized tuff, a result of vapor phase crystallization, and of tan and red ferruginous shale and siltstone.
The author has identified the following significant results. Mineralogical differences between hydrothermally altered rocks and most unaltered rocks in south central Nevada cause visible and near infrared (0.45-2.4 micron) spectral reflectance differences which can be used to discriminate broad categories of rocks in multispectral images. The most important mineralogical differences are the increased abundance of goethite, hematite, jarosite, alunite, montmorillonite, and kaolinite in the altered zones. Because of the wavelength positions and widths of the LANDSAT MSS bands, these spectral differences are not apparent in individual or color infrared composite MSS images. The technique developed to enhance these subtle spectral differences combines ratioing of the MSS bands and contrast stretching. Field evaluation of color-ratio composite shows that, after exclusion of alluvial areas, approximately 80% of the green and brown color patterns are related to hydrothermal alteration. The remaining 20% consists mainly of pink hematitic crystallized tuff and tan or red ferruginous shale and siltstone.
The basement rocks of Manicouagan exhibit a wide compositional range (40-72% SiO2). Least squares mixing calculations indicate that the average composition of the Manicouagan melt sheet can be modeled for 9 major and 11 trace elements by a mixture of 4.5% anorthosite, 55.5% mafic gneiss, and 40.0% tan gneiss with a granitic-granodioritic composition. The underrepresentation of anorthosite relative to its present distribution is considered. The homogeneous composition of the melt (57.75 + or - 1.21% SiO2) relative to that of the postulated target is explained in a model outlining the dynamic conditions existing during the formation of the melt and its accompanying movement into the excavated cavity.
The rheological behavior of newly developd Celion 6000/N-phenylnadimide modified PMR polyimide and PMR-15 composites was investigated. The dynamic mechanical properties were correlated with the structure of N-phenylnadimide modified PMR polyimides. The storage modulus (G'), loss modulus (G''), and loss tangent (tan delta) of four composite systems were measured over a temperature range from -150 to 400 C. Three well defined peaks were seen in the regions of 360, 100, and -120 C, corresponding to the alpha, beta, and gamma relaxations, respectively, of the matrix resins. The activation energies of the alpha, beta, and gamma relaxations were estimated to be 232, 60, and 14 kcal/mole, respectively, for PMR-15. Addition of N-phenylnadimide to the PMR-15 composition lowered the glass transition temperature and the activation energies of PMR-15 polyimide. The dynamic mechanical data appear to be consistent with the formation of a copolymer from N-phenylnadimide and a PMR-15 prepolymer.
Effects of an optically thin plane-parallel scattering atmosphere on radiometric imaging from the zenith of a specific surface-type are analyzed. The surface model was previously developed to describe arid steppe, where the sparse vegetation forms dark vertical protrusions from the bright soil-plane. The analysis is in terms of the surface reflectivity to the zenith r sub p for the direct beam, which is formulated as r sub p = r sub i exp (-s tan theta sub 0), where v sub i is the Lambert law reflectivity of the soil, the protrusions parameters s is the projection on a vertical plane of protrusions per unit area and theta sub 0 is the zenith angle. The surface reflectivity r sub p is approximately equal to that for the global irradiance (which is directly measured in the field) only for a narrow range of the solar zenith angles. The effects of the atmosphere when imaging large uniform areas of this type are comparable to those in imaging a Lambert surface with a reflectivity r sub p. Thus, the effects can be approximated by those in the case of a dark Lambert surface (analyzed previously), inasmuch as r sub p is smaller than the soil reflectivity r sub i for any off-zenith illumination. The surface becomes effectively darker with increasing solar zenith angle. Adjacency effects of a reflection from one area and scattering in the instantaneous field of view (object pixel) are analyzed as cross radiance and cross irradiance.
The Woo-Tan-Massey quantum-mechanical theory of dilute mixtures of He-3 in liquid He-4 is extended to incorporate superfluid flow. Then statistical-mechanical principles are employed to find explicit formulas for thermodyanmic and hydrodynamic properties of mixtures, such as internal energy, free energy, entropy, pressure, chemical potential, and normal-fluid and superfluid densities. This paper is the first in a planned series that applies methods originally developed for pure liquid He-4 to dilute mixtures as a means of establishing a comprehensive theory that includes a theoretical bridge between a microscopic description of the mixtures and a hydrodynamic two-fluid model. Ultimately effects of applied electric and magnetic fields on dilute solutions are also planned to be treated.
The window controller developed for the computer animation system (TAN) of the human-body modeling and positioning system TEMPUS (Badler et al., 1983) is characterized, and its operation is illustrated with diagrams. The controller is associated with a screen viewport and comprises five nested squares related to five modifications of the window, including zooming in and out, translation, locking plus translation, and extension of extremes plus translation. The variations of the controller and its limitations are considered, and its advantages over the use of a miniworld in a separate viewport are indicated.
A simple model for frictional slip on pre-existing faults that considers the local stress state near the fault and the effect of non-hydrostatic fluid pressures predicts that low-angle normal faulting is restricted to areas of the crust characterized by low differential stress and nearly lithostatic fluid pressures. The model considers frictional slip on a cohesionless low-angle normal fault governed by the failure criterion tau = mu sub f (sigma (*) sub n) =mu sub f (sigma sub n - P sub f) where tau and sigma sub n are the shear and normal stresses across the fault plane, mu sub f is the static coefficient of friction, and P sub f is the pore fluid pressure. As a first approximation, the model considers a vertical greatest principal compressive stress, sigma sub 1. It is apparent that if slip on low-angle normal faults is governed by the avove frictional failure criterion, slip on the low-angle normal fault occurs only if the least effective principal stress, sigma (*) sub 3 = sigma sub 3 - P sub f, is tensile, whenever tan superscrip -1(mu sub f d, where d is the dip of the fault. If detachment faulting occurs at any significant depth in the crust, P sub f sigma sub 3 is required. In light of this conclusion I allow P sub f to vary as necessary to allow slip on the low-angle normal fault.
Spectral albedo, A sub n, for the direct solar beam is defined as A sub n (r sub i,s, theta sub 0) = r sub i exp(-s tan theta sub 0)1-I(s) where I(s) is the integral over all reflection angles describing the interception by the absorbing plants of the flux reflected from the soil, r sub i soil reflectance, assumed Lambertian, S the projection on a vertical plane of plants per unit surface area, and theta sub 0 is the solar zenith angle. Hemispheric reflectance for the direct solar beam equals 1-I(s) times the reflectance to the zenith. The values of s of 0.1, 0.2, and 0.3 respectively quantify sparse, moderately dense, and very dense desert scrub. Thin plants are assumed to be of negligible thermal inertia, and thus directly yield the absorbed insolation to the atmosphere. Surface thermal inertia is therefore effectively reduced. The ratio of surface roughness height to plant height is parameterized for sparse, moderately dense, and very dense desert-scrub as a function of s based on data expressing the dependence of this ratio on plant silhouette.
A form of sulfur that is white at room temperature and very fluffy in texture has been found in laboratory experiments on the effects of vacuum sublimation (evaporation) on solid sulfur. This work is an outgrowth of proton sputtering experiments on sulfur directed toward understanding Jovian magnetospheric effects on the surface of Io. Fluffy white sulfur is formed on the surface of solid yellow, tan, or brown sulfur melt freezes in vacuum by differential (fractional) evaporation of two or more sulfur molecular species present in the original sulfur; S(8) ring sulfur is thought to be the dominant sublimination phase lost to the vacuum sink, and polymeric chain sulfur S(u) the dominant residual phase that remains in place, forming the residual fluffy surface layer. The reflectance spectrum of the original sulfur surface is greaty modified by formation of the fluffy layer: the blue absorption band-edge and shoulder move 0.05 to 0.06 microns toward shorter wavelengths resulting in a permanent increase in reflectivity near 0.42 to 0.46 microns; the UV reflectivity below 0.40 microns is reduced. This form of sulfur should exist in large quantity on the surface of Io, especially in hotspot regions if there is solid free sulfur there that has solidified from a melt. Its color and spectra will indicate relative crystallization age on a scale of days to months and/or surface temperature distribution history.
It is shown here that the experimental results of Newman (1985) and Tan et al. (1986) regarding the loss of oxygen interstitials during 450 C annealing of Czochralski silicon are consistent with the recently proposed model of Borenstein, Peak, and Corbett (1986) for thermal donor formation. Calculations were carried out for TD cores corresponding to O2, O3, O4, and/or O5 clusters. A simple model which attempts to capture the essential physics of the interstitial depletion has been constructed, and is briefly described.