Preferred frequencies for SETI observations

SETI observational programs conducted over the last two decades, and most of those planned for the near future, have concentrated on searching for signals at microwave frequencies. Considerations of signal-to-noise ratio at the receiving end indicate that this is the correct approach if the broadcasting society is not concerned with directionality and transmits into a fairly large solid angle. However, if that society desires to transmit only a highly directional beacon, then it is not now possible, given our lack of knowledge of advanced space technology, to predict reliably whether microwave or infrared wavelengths are to be preferred in an optimum search program. Given the realities of current terrestrial technology, either the centimeter or millimeter domain is to be preferred to the infrared, independent of considerations of directionality. In any event, there does not appear to be any cosmically unique (“magic”) frequency at which to conduct SETI.     

Modeling of ionospheric parameter variations in East Asia during the moderate geomagnetic disturbances

The results of modeling of ionospheric disturbances observed in the East Asian region during moderate storms are presented. The numerical model for ionosphere–plasmasphere coupling developed at the ISTP SB RAS is used to interpret the data of observations at ionospheric stations located in the longitudinal sector of 90–130°E at latitudes from auroral zone to equator. There is obtained a reasonable agreement between measurements and modeling results for winter and equinox. In the summer ionosphere, at the background of high ionization by the solar EUV radiation in the quiet geomagnetic period the meridional thermospheric wind strongly impacts the electron concentration in the middle and auroral ionosphere. The consistent calculations of the thermospheric wind permit to obtain the model results which are closer to summer observations. The actual information about the space-time variations of thermosphere and magnetosphere parameters should be taken into account during storms.     

Lithium micro-battery development at the Jet Propulsion Laboratory

Recent successes in the effort to miniaturize spacecraft components using MEMS technology, integrated passive components, and low power electronics have driven the need for very low power, low profile, low mass micro-power sources for micro/nanospacecraft applications. Recent work at JPL has focused upon developing thin film/micro-batteries compatible with temperature sensitive substrates. A process to prepare crystalline LiCoO₂ films with RF sputtering and moderate (<700°C) annealing temperature has been developed. Thin film batteries with cathode films prepared with this process have specific capacities approaching the practical limit for LiCoO₂, with acceptable rate capabilities and discharge voltage profiles. Solid-state micro-scale batteries have also been fabricated with feature sizes on the order of 50 microns     

Effects of bioreactor retention time on aerobic microbial decomposition of CELSS crop residues.

The focus of resource recovery research at the KSC-CELSS Breadboard Project has been the evaluation of microbiologically mediated biodegradation of crop residues by manipulation of bioreactor process and environmental variables. We will present results from over 3 years of studies that used laboratory- and breadboard-scale (8 and 120 L working volumes, respectively) aerobic, fed-batch, continuous stirred tank reactors (CSTR) for recovery of carbon and minerals from breadboard grown wheat and white potato residues. The paper will focus on the effects of a key process variable--bioreactor retention time--on response variables indicative of bioreactor performance. The goal is to determine the shortest retention time that is feasible for processing CELSS crop residues, thereby reducing bioreactor volume and weight requirements. Pushing the lower limits of bioreactor retention times will provide useful data for engineers who need to compare biological and physicochemical components. Bioreactor retention times were manipulated to range between 0.25 and 48 days. Results indicate that increases in retention time lead to a 4-fold increase in crop residue biodegradation, as measured by both dry weight losses and CO2 production. A similar overall trend was also observed for crop residue fiber (cellulose and hemicellulose), with a noticeable jump in cellulose degradation between the 5.3 day and 10.7 day retention times. Water-soluble organic compounds (measured as soluble TOC) were appreciably reduced by more than 4-fold at all retention times tested. Results from a study of even shorter retention times (down to 0.25 days), in progress, will also be presented.     

FEM code simulation of the magnetospheric proton fluxes

We report a study of the numeric solution to the diffusive transport equation for energetic protons magnetically trapped in the Earth's equatorial magnetosphere. The analysis takes into account the pertinent physical processes in this region, including deceleration of protons by Coulomb collisional interactions with free and bound electrons, the charge exchange process, cosmic ray albedo neutron decay source, and electric and magnetic radial diffusion. These results were obtained using the Finite Element Method with magnetic moment and geomagnetic L-shell as free variables. Steady state boundary conditions were imposed at L=1 as zero distribution function and at L=7 with proton distribution function extracted from ATS 6 satellite observations. The FEM-code yields unidirectional proton flux in the energy range of 0.1–1000 MeV at the equatorial top of the geomagnetic lines, and the results are found to be in satisfactorily agreement with the empirical NASA AP-8 model proton flux within the energy range of 0.5–100 MeV. Below 500 keV, the empirical AP-8 model proton fluxes are several orders of magnitude greater than those computed with the FEM-code at L<3. This discrepancy is difficult to explain by uncertainties of boundary spectrum parameters or transport coefficients.     

Abiogenic synthesis of pyrimidine nucleotides in solid state by vacuum ultraviolet radiation.

The abiogenic synthesis of pyrimidine nucleotides in solid state has been investigated. Our experiment indicates that natural nucleotides are produced in thin films prepared from nucleoside and inorganic phosphate by irradiating with vacuum ultraviolet light (VUV, lambda=100-200 nm). We have investigated the influence of the type of nucleic acids base (thymidine, cytosine, uracil) and the structure of sugar moiety (ribose or deoxyribose) on the course and yield of reaction. We compared the action of vacuum ultraviolet light with action of gamma-radiation, heat and biology significant UV (254 nm) which have been investigated earlier. The occurrence of these reaction in open space is discussed.     

Super-optimal CO2 reduces wheat yield in growth chamber and greenhouse environments.

Seven growth chamber trials (six replicate trials using 0.035, 0.12, and 0.25% CO2 in air and one trial using 0.12, 0.80, and 2.0% CO2 in air) and three replicate greenhouse trials (0.035, 0.10, 0.18, 0.26, 0.50, and 1.0% CO2 in air) compare the effects of super-optimal CO2 on the seed yield, harvest index, and vegetative growth rate of wheat (Triticum aestivum L. cvs. USU-Apogee and Veery-10). Plants in the growth chamber trials were grown hydroponically under fluorescent lamps, while the greenhouse trials were grown under sunlight and high pressure sodium lamps and in soilless media. Plants in the greenhouse trials responded similarly to those in the growth chamber trials; maximum yields occurred near 0.10 and 0.12% CO2 and decreased significantly thereafter. This research indicates that the toxic effects of elevated CO2 are not specific to only one environment and has important implications for the design of bio-regenerative life support systems in space, and for the future of terrestrial agriculture.     

Infrared spectrometer PFS for the Mars 94 orbiter

Thin films containing a mixture of aliphatic (glycine) and aromatic (tryptophan or tyrosine) amino acids were exposed to a vacuum ultraviolet radiation (VUV) with wavelenghts 100–200 nm. Dipeptides (glycyl-tryptophan and glycyl-tyrosine) were synthesized in these conditions. We compared the actions of VUV and γ-radiation. Polymerization is an essential step in prebiological evolution and we have shown that this stage probably occured over an early Solar system history.     

Solar-proton polar-cap intensity structures as a test of magnetic field models

The entry of energetic solar protons to the polar caps offers an interesting way to test models of the geomagnetic field. In this brief report, we present a comparison between SAMPEX observations of solar-particle intensity structure during a polar cap traversal with numerical trajectory calculations using the IGRF + T96 field model.     

Digital system design in the presence of single event upsets

The authors consider the effects of single event upsets (SEUs) on digital systems, and show techniques for designing reliable systems with current levels of SEU protection. Three main systems are discussed: main memory, logic, and cache memory. A design for the main and cache memory subsystems that are SEU protected is also described. With SEU defined in bit days p, and using single error correction, it is shown that for all subsystems considered, an effective upset rate which is proportional to the product of p² and the time between corrections, or scrub time, can be obtained. Data for memory chip size and performance derived from the gallium-arsenide (GaAs) pilot lines funded by the Defense Advanced Research Projects Agency (DARPA) throughout the 1980s are used