The Use of Computers in Editing and Composition

The modern digital computer is rapidly permeating all areas of our highly industrialized society-from agriculture to education-from process control to zoology. Printing and publishing and allied fields involved in graphic communications have been changing rapidly in this decade as the digital computer and associated peripheral devices have made rapid inroads in the graphic communications process. This paper describes the nature of the impact which the digital computer has had, and is making, upon today's graphic communications, particularly upon the editing and composition functions. A prediction of future impact is also presented.     

Pointing and Stability Requirements for Earth Orbital Experiments

Experiments for manned and unmanned space facilities of the next decade will impose stringent requirements for accurately pointing and/or maintaining stability of the space platforms over extended periods. Potential experiment programs identified to date in various NASA-and contractor-sponsored studies have been reviewed in order to define critical values and ranges for the following pointing/stability parameters: 1) pointing accuracy, 2) line-of-sight stability, 3) angular rate, and/or 4) acceleration level. The most stringent requirements were found to be in the research categories of: stellar and solar astronomy, earth observations, space physics, communications and navigation, and space biology.     

ATS-6 Technical Aspects of the Health/Education Telecommunications Experiment

The Health/Education Telecommunications (HET) Experiment involved six different experiments conducted under the auspices of the Department of Health, Education, and Welfare (HEW) with technical assistance from NASA. The HET Experiment on ATS-6 was operated and controlled from a network coordination center in Denver, Colo., which included a 4-and 6-GHz Earth station. The HET Experiment used remote Earth terminals with 3-m-diameter dishes having a 35 dB gain at 2.5 GHz. In addition, comprehensive terminals operating at both C-band and S-band were used for communications with Alaska. The total network involved a complex of satellite and land links at C-band, S-band, and very high frequency (VHF), using the ATS-1, ATS-3, and ATS-6 satellites. The network performance exceeded expectations with remote terminal operations exhibiting a peak-to-peak signal to weighted rms noise ratio of 49 dB at least 99 percent of the time. The remote site operators performed well and were well motivated although they had little previous technical experience.     

The solar wind interaction with the geomagnetic field

A review is presented of the interaction of the solar wind with the magnetic field of the earth. The material is developed primarily from an observational point of view. The early observations are covered through late 1963, with primary emphasis on the sunward interaction region. The historical review of the early results is discussed in terms of the significant contributions of each satellite observation and in the light of our present concept of the solar wind-geomagnetic field interaction. Subsequent to 1963 the observations tend to overlap such that a strictly historical treatment is not tractable and the material is presented from a phenomenological approach. The daytime and night-time hemispheres are covered separately in terms of the significant and separable phenomena which dominate the structure and dynamics of these two regions. Satellite and deep space probe data are compared with relevant theory. Further observational eflorts needed to improve our understanding of the details of the solar wind-geomagnetic field interaction are also discussed.     

Biologically enhanced energy and carbon cycling on Titan?

With the Cassini-Huygens Mission in orbit around Saturn, the large moon Titan, with its reducing atmosphere, rich organic chemistry, and heterogeneous surface, moves into the astrobiological spotlight. Environmental conditions on Titan and Earth were similar in many respects 4 billion years ago, the approximate time when life originated on Earth. Life may have originated on Titan during its warmer early history and then developed adaptation strategies to cope with the increasingly cold conditions. If organisms originated and persisted, metabolic strategies could exist that would provide sufficient energy for life to persist, even today. Metabolic reactions might include the catalytic hydrogenation of photochemically produced acetylene, or involve the recombination of radicals created in the atmosphere by ultraviolet radiation. Metabolic activity may even contribute to the apparent youth, smoothness, and high activity of Titan's surface via biothermal energy.     

The Accretion, Composition and Early Differentiation of Mars

The early development of Mars is of enormous interest, not just in its own right, but also because it provides unique insights into the earliest history of the Earth, a planet whose origins have been all but obliterated. Mars is not as depleted in moderately volatile elements as are other terrestrial planets. Judging by the data for Martian meteorites it has Rb/Sr 0.07 and K/U 19,000, both of which are roughly twice as high as the values for the Earth. The mantle of Mars is also twice as rich in Fe as the mantle of the Earth, the Martian core being small (20% by mass). This is thought to be because conditions were more oxidizing during core formation. For the same reason a number of elements that are moderately siderophile on Earth such as P, Mn, Cr and W, are more lithophile on Mars. The very different apparent behavior of high field strength (HFS) elements in Martian magmas compared to terrestrial basalts and eucrites may be related to this higher phosphorus content. The highly siderophile element abundance patterns have been interpreted as reflecting strong partitioning during core formation in a magma ocean environment with little if any late veneer. Oxygen isotope data provide evidence for the relative proportions of chondritic components that were accreted to form Mars. However, the amount of volatile element depletion predicted from these models does not match that observed — Mars would be expected to be more depleted in volatiles than the Earth. The easiest way to reconcile these data is for the Earth to have lost a fraction of its moderately volatile elements during late accretionary events, such as giant impacts. This might also explain the non-chondritic Si/Mg ratio of the silicate portion of the Earth. The lower density of Mars is consistent with this interpretation, as are isotopic data. ⁸⁷Rb-⁸⁷Sr, ¹²⁹I-¹²⁹Xe, ¹⁴⁶Sm-¹⁴²Nd, ¹⁸²Hf-¹⁸²W, ¹⁸⁷Re-¹⁸⁷Os, ²³⁵U-²⁰⁷Pb and ²³⁸U-²⁰⁶Pb isotopic data for Martian meteorites all provide evidence that Mars accreted rapidly and at an early stage differentiated into atmosphere, mantle and core. Variations in heavy xenon isotopes have proved complicated to interpret in terms of ²⁴⁴Pu decay and timing because of fractionation thought to be caused by hydrodynamic escape. There are, as yet, no resolvable isotopic heterogeneities identified in Martian meteorites resulting from ⁹²Nb decay to ⁹²Zr, consistent with the paucity of perovskite in the martian interior and its probable absence from any Martian magma ocean. Similarly the longer-lived ¹⁷⁶Lu-¹⁷⁶Hf system also preserves little record of early differentiation. In contrast W isotope data, Ba/W and time-integrated Re/Os ratios of Martian meteorites provide powerful evidence that the mantle retains remarkably early heterogeneities that are vestiges of core metal segregation processes that occurred within the first 20 Myr of the Solar System. Despite this evidence for rapid accretion and differentiation, there is no evidence that Mars grew more quickly than the Earth at an equivalent size. Mars appears to have just stopped growing earlier because it did not undergo late stage (>20 Myr), impacts on the scale of the Moon-forming Giant Impact that affected the Earth.     

Fate of prebiotic adenine

Equilibrium adsorption isotherm data for the purine base adenine has been obtained on several prebiotically relevant minerals by frontal analysis using water as a mobile phase. Adenine is far displaced toward adsorption on pyrite (FeS2), quartz (SiO2), and pyrrhotite (FeS), but somewhat less for magnetite (Fe3O4) and forsterite (Mg2SiO4). The prebiotic prevalence of these minerals would have allowed them to act as a sink for adenine; removal from the aqueous phase would confer protection from hydrolysis as well, establishing a nonequilibrium thermodynamic framework for increased adenine synthesis. Our results provide evidence that adsorption phenomena may have been critical for the primordial genetic architecture.     

Analytic models and postprocessing techniques for UWB SAR

The latest generation of fully polarimetric, ultra wideband (UWB), wide angle, low frequency, foliage and ground-penetrating synthetic aperture radars (SARs) record huge amounts of data that must be processed to focus high quality images. At the same time only a few small subimages contain important information. We investigate the relationship between the focused image and the reflectivity profile and show that a linear shift-invariant model adequately represents the overall process when the focusing is done with a backprojection algorithm over a constant integration angle. The derived signal model can be used to replace many computationally expensive processing techniques, previously performed on the raw data, with equivalent postprocessing algorithms which can be applied selectively to subimages.