Shielding against galactic cosmic rays.

Ions of galactic origin are modified but not attenuated by the presence of shielding materials. Indeed, the number of particles and the absorbed energy behind most shield materials increases as a function of shield thickness. The modification of the galactic cosmic ray composition upon interaction with shielding is the only effective means of providing astronaut protection. This modification is intimately connected with the shield transport properties and is a strong function of shield composition. The systematic behavior of the shield properties in terms of microscopic energy absorption events will be discussed. The shield effectiveness is examined with respect to conventional protection practice and in terms of a biological endpoint: the efficiency for reduction of the probability of transformation of shielded C3H10T1/2 mouse cells. The relative advantage of developing new shielding technologies is discussed in terms of a shield performance as related to biological effect and the resulting uncertainty in estimating astronaut risk.     

Consideration in selecting crops for the human-rated life support system: a Linear Programming model.

A Linear Programming model has been constructed which aids in selecting appropriate crops for CELSS (Controlled Environment Life Support System) food production. A team of Controlled Environment Agriculture (CEA) faculty, staff, graduate students and invited experts representing more than a dozen disciplines, provided a wide range of expertise in developing the model and the crop production program. The model incorporates nutritional content and controlled-environment based production yields of carefully chosen crops into a framework where a crop mix can be constructed to suit the astronauts' needs. The crew's nutritional requirements can be adequately satisfied with only a few crops (assuming vitamin mineral supplements are provided) but this will not be satisfactory from a culinary standpoint. This model is flexible enough that taste and variety driven food choices can be built into the model.     

Overview of nuclear fragmentation models and needs.

It has been known for some time that adequate assessment of spacecraft shield requirements and concomitant estimates of astronauts radiation exposures from galactic cosmic radiation requires accurate, quantitative methods for characterizing these radiation fields as they pass through thick absorbers. The main nuclear interaction processes involved are (1) nuclear elastic and inelastic collisions, and (2) nuclear breakup (fragmentation) and electromagnetic dissociation (EMD). Nuclear fragmentation and EMD are important because they alter the elemental and isotopic composition of the transported radiation fields. At present, there is no suitably accurate theory for predicting nuclear fragmentation cross sections for all collision pairs and energies of interest in space radiation protection. Typical cross-section differences between theory and experiment range from about 25 percent to a factor of two. The resulting errors in transported flux, for high linear energy transfer (LET) particles, are comparble to these cross-section errors. In this overview, theoretical models of heavy ion fragmentation currently used to generate input data bases for cosmic-ray transport and shielding codes are reviewed. Their shortcomings are discussed. Further actions needed to improve their accuracy and generality are presented.     

Hemispheric differences in the earth radiation budget derived from Nimbus-7 related to climate studies

Earth Radiation Budget (ERB) data from Nimbus-7 over the period November 1978 – June 1980 has consistently shown strong hemispheric differences when analyzed over different temporal and spatial scales. Hemispheric variations in time latitude cross sections of net and emitted radiation were found to be caused by changes in the Earth-Sun distance and continental effects.Maps of annual range for the entire Earth calculated from monthly averages showed areas of high and low variability of the different ERB parameters. The ERB of these regional areas were examined and most of the variability was found to lay in the large amplitude of the annual solar cycle. Variations in the global annual cycle of albedo /1/ are studied with respect to differences in latitudinal averaged albedo. The anomaly in the annual cycle of global averaged albedo was found to be caused by tropical albedo changes.     

Low altitude wind shear detection using airport surveillance radars

This paper describes an enhanced weather processor for the Federal Aviation Administration's Airport Surveillance Radar (ASR-9) that will include Doppler wind estimation for the detection of low altitude wind shear, scan-to-scan tracking to provide estimates of the speed and direction of storm movement and suppression' of spurious weather reports currently generated by the ASR-9's six-level weather channel during episodes of anomalous radar energy propagation (AP). This ASR-9 Wind Shear Processor (WSP) will be implemented as a retrofit to the ASR-9 through the addition of interfaces, receiving chain hardware and high-speed digital processing and display equipment. Thunderstorm activity in terminal airspace (the volume extending approximately 30 nmi from an airport and to 15,000 feet altitude) is an obvious safety issue and makes a significant overall contribution to delay in the United States commercial aviation industry. Analysis and on-line testing of the prototype ASR-9 WSP has confirmed that the system can provide operationally beneficial detection of low-altitude wind shear phenomena and enhanced weather situational awareness for Air Traffic Control teams     

Effect of enclosure shape on natural convection velocities in microgravity

A numerical analysis was performed to compare natural convection velocities in two-dimensional enclosures of various shape. The following shapes were investigated: circle, square, horizontal and upright 2 × 1 aspect ratio rectangles, horizontal and upright half-circles, diamond (square oriented with diagonal vertical) and triangle (equilateral and horizontal base). In all cases, the length scale in the various dimensionless parameters, such as Rayleigh number, is defined as the diameter of the equal area circle. Natural convection velocities were calculated for Rayleigh numbers of 100 and 500 with the temperature difference taken to be across (a) the maximum horizontal dimension, (b) the median horizontal line (line through centroid) and (c) the horizontal distance such that the temperature gradient is the same for shapes of equal area. A Rayleigh number of 1000 is within the “low Rayleigh number” range for agreement with first order theory for circular enclosures. A Rayleigh number of 5000 is slightly out of this range. For the class of shapes including the square, upright half-circle and upright rectangle, the computed velocities were found to agree very closely with that of the equal area circle when the temperature difference is taken to be across the maximum horizontal dimension [condition (a)]. The velocities for the horizontal rectangle and half circle were found to be approximately one-half that of the equal area circle for the same condition. Better overall agreement among all shapes was obtained by setting the temperature difference across a distance such that the temperature gradients were equal for shapes of equal area.     

Adaptive Estimation for a System with Unknown Measu rement Bias

An adaptive state estimator for passive underwater tracking of maneuvering targets is developed. The state estimator is designed specifically for a system containing unknown or randomly switching biased measurements. In modeling the stochastic system, it is assumed that the bias sequence dynamics can be modeled by a semi-Markov process. By incorporating the semi-Markovian concept into a Bayesian estimation technique, an estimator consisting of a bank of parallel, adaptively weighted, Kalman filters has been developed. Despite the large and randomly varying measurement biases, the proposed estimator, provides an accurate estimate of the system states.     

Generalized Problem of Two Fixed Centers or the Darboux-Gredeaks Problem

A brief review of publications on the problem of two fixed centers is given, including its generalizations and astronomical applications. A comparison of the Darboux potential with that of Eve Gredeaks is made. An account of the basic points of development of modern high-precision theories of the motion of planetary satellites, based on the Gredeaks’ intermediate orbit, is given.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 194–200.Original Russian Text Copyright © 2005 by Lukyanov, Emeljanov, Shirmin.Dedicated to the memory of Professor Evgenii Petrovich Aksenov     

1E 1740.7-2942 revisited: Confirmation of its identification with the core of a double sided radio jet structure

After more than two years of successful in-orbit operations, the γ-ray coded aperture SIGMA telescope has accumulated 800 hours of live-time observations of the Galactic Center region, including the remarkable hard source identified with the X-ray source 1E 1740.7–2942. The long-term behavior of the soft γ-ray emission of 1E 1740.7–2942, as determined from the SIGMA survey, supplemented with previously available soft γ-ray data, leads to its identification with a singular radio source, which consists of a double sided radio jet emanating from a compact variable core whose variability is correlated with that of the soft γ-ray source. The compact radio core, which lies well inside the improved soft γ-ray (40–150 keV) error circle (27″ radius) derived from the high-resolution SIGMA survey, is also inside the ROSAT and TTM error circle derived respectively in the soft and hard X-ray bands.     

"SYMBIOSE" SYstem for Microgravity BIOregenerative Support of Experiments.

SYMBIOSE is an ESA supported research and development program which aims at establishing a first pilot model of a closed ecological system, compatible with operation in weightlessness conditions, and dedicated to scientific investigations in the microgravity environment. It integrates microalgal photosynthesis within an artificial ecosystem featuring a symbiotic strain of Chlorella (241 .80, Gottingen), which synthesizes and excretes substantial amounts of maltose, and is further looped on a consumer compartment. A technological concept has been developed. It is presently being integrated in order to gain knowledge on the system dynamics, and ultimately demonstrate the feasibility of such a biotechnology. Preliminary work on the photosynthetic metabolism of this microalga is being undertaken in order 1) to support later a mathematical formalisation of the dynamics of this artificial ecosystem, and, on this basis, 2) to compensate for its lack of stability with model-based external control. The most recent results are presented, along with a new design of the photobioreactor which integrates efficient light energy capture, microgravity compatible gas transfer and reduced shear stress.