Inversion algorithms for the microwave remote sensing of soil moisture. Experiments with swept frequency microwaves

Two experiments were performed employing swept frequency microwaves for the purpose of investigating the reflectivity from soil volumes containing both discontinuous and continuous changes in subsurface soil moisture content. Discontinuous moisture profiles were artificially created in the laboratory while continuous moisture profiles were induced into the soil of test plots by the environment of an agricultural field. The reflectivity for both the laboratory and field experiments was measured using bi-static reflectometers operated over the frequency ranges of 1.0 to 2.0 GHz and 4.0 to 8.0 GHz. Reflectivity models that considered the discontinuous and continuous moisture profiles within the soil volume were developed and compared with the results of the experiments. This comparison shows good agreement between the smooth surface models and the measurements. In particular the comparison of the smooth surface multi-layer model for continuous moisture profiles and the yield experiment measurements points out the sensitivity of the specular component of the scattered electromagnetic energy to the movement of moisture in the soil

Code 672 observational science branch computer networks

In general, networking increases productivity due to the speed of transmission, easy access to remote computers, ability to share files, and increased availability of peripherals. Two different networks within the Observational Science Branch are described in detail

Terrain analysis using radar shape-from-shading

This paper develops a maximum a posteriori (MAP) probability estimation framework for shape-from-shading (SFS) from synthetic aperture radar (SAR) images. The aim is to use this method to reconstruct surface topography from a single radar image of relatively complex terrain. Our MAP framework makes explicit how the recovery of local surface orientation depends on the whereabouts of terrain edge features and the available radar reflectance information. To apply the resulting process to real world radar data, we require probabilistic models for the appearance of terrain features and the relationship between the orientation of surface normals and the radar reflectance. We show that the SAR data can be modeled using a Rayleigh-Bessel distribution and use this distribution to develop a maximum likelihood algorithm for detecting and labeling terrain edge features. Moreover, we show how robust statistics can be used to estimate the characteristic parameters of this distribution. We also develop an empirical model for the SAR reflectance function. Using the reflectance model, we perform Lambertian correction so that a conventional SFS algorithm can be applied to the radar data. The initial surface normal direction is constrained to point in the direction of the nearest ridge or ravine feature. Each surface normal must fall within a conical envelope whose axis is in the direction of the radar illuminant. The extent of the envelope depends on the corrected radar reflectance and the variance of the radar signal statistics. We explore various ways of smoothing the field of surface normals using robust statistics. Finally, we show how to reconstruct the terrain surface from the smoothed field of surface normal vectors. The proposed algorithm is applied to various SAR data sets containing relatively complex terrain structure

An Analysis of Kinetic Response Variability

Studies evaluating variability of force as a function of absolute force generated are synthesized. Inconsistencies in reported estimates of this relationship are viewed as a function of experimental constraints imposed. Typically, within-subject force variability increases at a negative accelerating rate with equal increments in force produced. Current pulse-step and impulse variability models are unable to accommodate this description, although the notion of efficiency is suggested as a useful construct to explain the description outlined

NOSS altimeter algorithm specifications

A description of all algorithms required for altimeter processing is given. Each description includes title, description, inputs/outputs, general algebraic sequences and data volume. All required input/output data files are described and the computer resources required for the entire altimeter processing system were estimated. The majority of the data processing requirements for any radar altimeter of the Seasat-1 type are scoped. Additions and deletions could be made for the specific altimeter products required by other projects

Data documentation for the bare soil experiment at the University of Arkansas

The reflectivities of several controlled moisture test plots were investigated. These test plots were of a similar soil texture which was clay loam and were prepared to give a desired initial soil moisture and density profile. Measurements were conducted on the plots as the soil water redistributed for both long term and diurnal cycles. These measurements included reflectivity, gravimetric and volumetric soil moisture, soil moisture potential, and soil temperature

The mount Tawai Peridotite, north Borneo

The Mount Tawai peridotite is a batholith, elongate north-south, situated between the Kinabatangan and Labuk rivers in the North Borneo ultrabasic belt. The surrounding country rocks are Upper Cretaceous and Tertiary sediments and volcanics which strike predominantly E.N.E. They are separated from the peridotite by a fault breccia which contains inclusions of metamorphic rocks. The batholith comprises at least three partially separated tectonic units, the largest of which is the Main Tawai block. Theouter parts of the tectonic units exhibit a crude gneissose foliation and peripheral serpentinization. The batholith is composed mainly of harzburgite with scarce dunite, pyroxenite and gabbro phases. The dunite occurs in lenticular pods which dip steeply westward in the Main Tawai block. Some of the dunite lenses contain thin chromite bands showing evidence of rudimentary gravity stratification. The harzburgite is composed mainly of forsterite and enstatite with only minor endiopside. The alumina content of the enstatite varies from 1.3 to 7.4 per cent and that of the endiopside from 2.9 to 7.2 per cent. The dunite bandscontain forsterite and chrome spinel, the composition of the latter varying from cr(_65.5) AL(_32.2) (Mg(_68.1)) to cr(__32.6) AL(_66 .9) (Mg(_63.8)) on Thayer's (1946) shortened formula. The gabbroic rocks are irregularly distributed within the batholith occurring mainly as tectonic inclusions. Both the ultrabasic and basic rocks are considered to have been derived from the same parent magma. The absence of anorthite from the ultrabasic assemblages is explained by an initial phase of differentiation at very high temperature and pressure which suppressed the precipitation of plagioclase but favoured the introduction of alumina into the pyroxenes. During the initial phase of differentiation only olivine, enstatite, endiopside, and spinel were precipitated, but there must have been frequent but short-lived intervals in which only olivine and spinel were precipitated; these are thought to have accumulated in hollows and channels on the floor of a crystal pile. A systematic increase of alumina in the pyroxenes and spinels of the Main Tawai block has been traced and is attributed to a crystallisation sequence. A gabbroic phase is thought to have been precipitated on top of the ultrabasic crystal pile following a drop in temperature which resulted in the precipitation of plagioclase and the lowering of the Mg/Fe ratio in the pyroxene and olivine. A calculation of the average composition of the rocks of the North Borneo belt is in close agreement with the average mantle composition suggested by Ringwood (1959). This evidence together with the high temperature and pressure conditions needed to explain the ultrabasic assemblages has led to the conclusion that the parent magma of the Mount Tawai complex was derived by fusion of upper mantle material. After or during the final stages of differentiation the gabbroic fraction was injected into the crust creating a pre-heated path up which the hot, already-differentiated peridotite rose as a series of almost crystalline units. During this stage a gneissose folliation developed roughly parallel to the sides of the intrusive units. Thermal metamorphism of the country rocks to garnet amphibolite fades accompanied the process. After cooling beneath the surface the intrusive units were serpentinised and emplaced in their present position by faulting, which also disrupted the thermal metamorphic aureole. Late lime bearing solutions, deposited calc-silicate veins and altered some of the gabbro to rodingite. The final emplacement had profound effects on the drainage system and occurred in late or post Pleistocene

Mars Observer Radar Altimeter Radiometer (MORAR)

The Mars Observer Project will permit the advancement of the state of the topographic and hypsometric knowledge of Mars to a level of 10 m or better over the surface of the planet Mars, the measurement of microwave surface brightness temperature of Mars with an accuracy of 15 to 20 K over 24 hours, and the measurement, globally, of surface returned power related to radar cross section with an accuracy of 1 dB and a repeatability of .5 dB. The MORAR Hardware Development, Ground Data Processing, and the Mission Operations will allow the accomplishment of these scientific objectives to define globally the topography of Mars at sufficient vertical resolution and spatial scale to address both large-scale geophysical and small-scale geologic problems, and to obtain global surface electrical and scattering properties of the upper several centimeters of the Martian surface for assessment of the composition, physical state, and volatile distribution of the surface