Radar-anomalous, high-altitude features on Venus

Over nearly all of the surface of Venus the reflectivity and emissivity at centimeter wavelengths are about 0.15 and 0.85 respectively. These values are consistent with moderately dense soils and rock populations, but the mean reflectivity is about a factor of 2 greater than that for the Moon and other terrestrial planets. Pettingill and Ford, using Pioneer Venus reflectivities and emissivities, found a number of anomalous features on Venus that showed much higher reflectivities and much lower emissivities with both values approaching 0.5. These include Maxwell Montes, a number of high regions in Aphrodite Terra and Beta Regio, and several isolated mountain peaks. Most of the features are at altitudes above the mean radius by 2 to 3 km or more. However, such features have been found in the Magellan data at low altitudes and the anomalies do not exist on all high structures, Maat Mons being the most outstanding example. A number of papers have been written that attempt to explain the phenomena in terms of the geochemistry balance of weathering effects on likely surface minerals. The geochemists have shown that the fundamentally basaltic surface would be stable at the temperatures and pressures of the mean radius in the form of magnetite, but would evolve to pyrite and/or pyrrhotite in the presence of sulfur-bearing compounds such as SO2. Pyrite will be stable at altitudes above 4 or 5 km on Venus. Although the geochemical arguments are rather compelling, it is vitally important to rationally look at other explanations for radar and radio emission measurements such as that presented by Tryka and Muhleman. The radar reflectivity values are retrieved from the raw Magellan backscatter measurements by fitting the Hagfors' radar scattering model in which a surface roughness parameters and a normal incidence electrical reflectivity are estimated. The assumptions of the theory behind the model must be considered carefully before the results can be believed. These include that the surface roughness exists only at horizontal scales large compared to the wavelength, the vertical deviations are gaussianly distributed, there is no shadowing, and that the reflection occurs at the interface of two homogeneous dielectric half-spaces. Probably all these conditions are violated at the anomalous features under discussion. The most important of these is the homogeneity of the near surface of Venus, particularly in highlands. Under the assumptions of the theory, all of the radio energy is reflected by the impedance jump at the very boundary. However, in heterogeneous soil some fraction of the illuminating energy is propagated into the soil and then scattered back out by impedance discontinuities such as rock, voids, and cracks. In light soils, the latter effect can overwhelm the scattering effects of the true surface and greatly enhance the backscatter power, suggesting a much higher value of an effective dielectric constant that would be estimated from Hagfors' model

Radar Investigation of Mars, Mercury, and Titan

Radar astronomy is the study of the surfaces and near surfaces of Solar System objects using active transmission of modulated radio waves and the detection of the reflected energy. The scientific goals of such experiments are surprisingly broad and include the study of surface slopes, fault lines, craters, mountain ranges, and other morphological structures. Electrical reflectivities contain information about surface densities and, to some extent, the chemical composition of the surface layers. Radar probes the subsurface layers to depths of the order of 10 wavelengths, providing geological mapping and determinations of the object’s spin state. Radar also allows one to study an object’s atmosphere and ionic layers as well as those of the interplanetary medium. Precise measurements of the time delay to surface elements provide topographic maps and powerful information on planetary motions and tests of gravitational theories such as general relativity. In this paper, we limit our discussion to surface and near-surface probing of Mercury, Mars, and Titan and review the work of the past decade, which includes fundamentally new techniques for Earth-based imaging. The most primitive experiments involve just the measurement of the total echo power from the object. The most sophisticated experiments would produce spatially resolved maps of the reflected power in all four Stokes’ parameters. Historically, the first experiments produced echoes from the Moon during the period shortly after World War II (see e.g. Evans 1962), but the subject did not really develop until the early 1960s when the radio equipment was sufficiently sensitive to detect echoes from Venus and obtain the first Doppler strip "maps" of that planet. The first successful planetary radar systems were the Continuous Wave (CW) radar at the Goldstone facility of the Caltech’s Jet Propulsion Laboratory and the pulse radar at the MIT Lincoln Laboratory. All of the terrestrial planets were successfully studied during the following decade, yielding the spin states of Venus and Mercury, a precise value of the astronomical unit, and a host of totally new discoveries concerning the surfaces of the terrestrial planets and the Moon. This work opened up at least a similar number of new questions. Although the early work was done at resolution scales on the order of the planetary radii, very rapid increases in system sensitivities improved the resolution to the order of 100 km, but always with map ambiguities. Recently, unambiguous resolution of 100 m over nearly the entire surface of Venus has been achieved from the Magellan spacecraft using a side-looking, synthetic aperture radar. Reviews of the work up to the Magellan era can be found in Evans (1962), Muhleman et al (1965), Evans & Hagfors (1968, see chapters written by G Pettengill, T Hagfors, and J Evans), and Ostro (1993). The radar study of Venus from the Magellan spacecraft was a tour de force and is well described in special issues of Science (volume 252, April 12, 1991) and in the Journal of Geophysical Research (volume 97, August 25 and October 25, 1992). Venus will not be considered in this paper even though important polarization work on that planet continues at Arecibo, Goldstone, and the Very Large Array (VLA). In this paper we review the most recent work in Earth-based radar astronomy using new techniques of Earth rotation, super synthesis at the VLA in New Mexico (operated by the National Radio Astronomy Observatory), and the recently developed "long-code" techniques at the Arecibo Observatory in Puerto Rico (operated by Cornell University). [Note: It was recently brought to our attention that the VLA software "doubles" the flux density of their primary calibrators. Consequently, it is necessary to half the radar power and reflectivity numerical values in all of our published radar results from the VLA/Goldstone radar.] The symbiotic relationship in these new developments for recent advances in our understanding of Mercury and Mars is remarkable. VLA imaging provides for the first time, unambiguous images of an entire hemisphere of a planet and the long-code technique makes it possible to map Mars and Mercury using the traditional range-gated Doppler strip mapping procedure [which was, apparently, developed theoretically at the Lincoln Laboratory by Paul Green, based on a citation in Evans (1962)]. Richard Goldstein was the first to obtain range-gated planetary maps of Venus as reported in Carpenter & Goldstein (1963). Such a system was developed earlier for the Moon as reported by Pettengill (1960) and Pettengill & Henry (1962). We first discuss the synthesis mapping technique

SIMULATING BST INTRODUCTION IN CALIFORNIA FOR DAIRY POLICY ANALYSIS

An econometric model is estimated to simulate the impact of introducing bovine somatotropin (BST) on the California dairy industry. Forecasts of 1991-94 milk production and prices without BST are compared to those with BST under the 1990 Farm Bill. The effects are evaluated under a range in assumptions, given the uncertainty about BST's commercial benefits and costs. Results indicate the aggregate returns of BST introduction for California are positive, but small, assuming no adverse consumer reaction.Agricultural and Food Policy, Research and Development/Tech Change/Emerging Technologies,

The effect of age and weight upon the blood volume of farm animals

The need for a knowledge of the amount of circulating blood in man and animal has stimulated investigators in many fields of research to study and apply various methods and techniques for the quantitative determination of blood volume. This has resulted in the controversies and in conflicting reports in the literature. Through these efforts to perfect methods and establish constant values for the different species much information has been acquired from which our present concepts have been formulated. The increasing popularity and adaptability of farm animals for nutritional, radiation and therapeutic studies using labeled elements and compounds require that acceptable blood volume figures be established for use in experimental interpretations of these results. Aside from the limited early results summarized by Dukes (1947) these for the growing bovine reported by Missouri workers (1931) and the studies with swine by Hansard et. al. (1951), few values have been reported on blood volume determination with farm animals. In the view of the limited information in the literature concerning the blood volume of the various species of farm animals, this study was initiated with the following objectives; (1) to determine an adaptable procedure for blood volume for the various species; (3) to establish an acceptable value for the blood volume of the various species at definite ages and weights; (4) to determine the limitations of the accepted procedure as affected by in vitre and in vive studies that make for variations in values reported; and, (5) to correlate the results of this study with values and methods reported in the literature

Combating Money Laundering and International Terrorism: Does the USA PATRIOT Act Require the Judicial System to Abandon Fundamental Due Process in the Name of Homeland Security?

The USA PATRIOT Act was part of a wave of legislation which reshaped national security policies while simultaneously restricting traditional civil liberties in response to the terrorist attacks of September 11. Among the many terrorism related provisions of the Act, the executive branch was given authority to freeze the assets of organizations in which there is a foreign interest suspected of funding terrorist organizations through the use of an asset blocking order pending further investigation. The Act further permits the use of classified information which will be subjected to only ex parte, in camera inspection by the judge presiding over a challenge to such an action as a means of supporting the government’s actions in freezing such assets. This article addresses the question of whether the government’s use of secret evidence to justify a challenged blocking order pursuant to the provisions of the Patriot Act represents a violation of the fundamental due process rights of an aggrieved party. The article first examines the rapidly developing body of legal precedent emerging from recent challenges to such blocking orders and the Government’s efforts to enforce such orders through the submission of “confidential and sensitive” evidence on an ex parte, in camera basis. The article also examines the legal and public policy arguments, both in favor of and against the continued use of such ex parte, in camera evidence as a part of judicial proceedings challenging blocking orders as well as some of the potential ramifications of such a course of action. What emerges from this analysis is the determination that while the provisions of the Act relating to the ex parte, in camera submission of evidence supporting the government’s allegations are alarming at first glance, the ultimate goal of cracking down on money laundering as an increasingly potent source of terrorist financing can only be supported by broad enforcement capabilities held in check by the unbiased members of the judiciary