Galactic cosmic ray transport methods: past, present, and future.

The development of the theory of high charge and energy (HZE) ion transport is reviewed. The basic solution behavior and approximation techniques will be described. An overview of the HZE transport codes currently available at the Langley Research Center will be given. The near term goal of the Langley program is to produce a complete set of one-dimensional transport codes. The ultimate goal is to produce a set of complete three-dimensional codes which have been validated in the laboratory and can be applied in the engineering design environment. Recent progress toward completing these goals is discussed.     

Oscillations of axial plant organs.

The tips of roots and shoots commonly show lateral movements as they grow forwards. These occur as both circumnutations (with long periods and large amplitudes) and micronutations (with short periods and small amplitudes). Their properties are reviewed, with emphasis on roots, and possible ways in which they could be regulated are discussed. The mechanisms could include long-range controls (for circumnutations) that depend on transmissible signals using steps common to gravitropism, and short-range controls (for micronutations) that operate within the elongation zone. The former are a property of the apex as a whole, while the latter may be confined to localized groups of cells. Simulation of nutations is presented with a view to isolating key physiological processes. However, this approach is limited by the current inadequate understanding of the growth mechanisms involved.     

A program to measure new energetic particle nuclear interaction cross sections.

The Transport Collaboration, consisting of researchers from institutions in France, Germany, Italy and the USA, has established a program to make new measurements of nuclear interaction cross sections for heavy projectiles (Z > or = 2) in targets of liquid H2, He and heavier materials. Such cross sections directly affect calculations of galactic and solar cosmic ray transport through matter and are needed for accurate radiation hazard assessment. To date, the collaboration has obtained data using the LBL Bevalac HISS facility with 20 projectiles from 4He to 58Ni in the energy range 393-910 MeV/nucleon. Preliminary results from the analysis of these data are presented here and compared to other measurements and to cross section prediction formulae.     

Performance analysis for DOA estimation algorithms: unification,simplification, and observations

Subspace based direction-of-arrival (DOA) estimation has motivated many performance studies, but limitations such as the assumption of an infinite amount of data and analysis of individual algorithms generally exist in these performance studies. The authors have previously proposed a unified performance analysis based on a finite amount of data and achieved a tractable expression for the mean-squared DOA estimation error for the multiple signal classification (MUSIC). Min-Norm, estimation of signal parameters using rotational invariance techniques (ESPRIT), and state-space realization algorithms. However, this expression uses the singular values and vectors of a data matrix, which are obtained by the highly nonlinear transformation of the singular value decomposition (SVD). Thus the effects of the original data parameters such as numbers of sensors and snapshots, source coherence and separations were not explicitly analyzed. The authors unify and simplify this previous result and derive a unified expression based on the original data parameters. They analytically observe the effects of these parameters on the estimation error     

Target motion analysis with multiple arrays: performance analysis

The performance analysis of source trajectory estimation using measurements provided by multiple platforms (or arrays) is studied. In numerous practical situations, the maneuvering ability of the receiver (e.g., a ship towing linear arrays) is limited, leading to the assumption that the observer motion is rectilinear and uniform. Even if this hypothesis appears quite restrictive, practical and tactical considerations fully justify its interest. This leads to consider multiple (platform) target motion analysis (denoted MTMA) and to analyze the performance of such trajectory estimation methods     

A baseband Doppler simulator for radar system development

Elementary electronics building blocks can be configured as a low-cost baseband Doppler simulator for developing the post-detector processing parts such as MTIs and MTDS of millimeter wave pulsed radars employing amplitude and phase channels. The challenge of narrow pulses in conjunction to low Doppler frequencies is handled here by CMOS switches and normal function generator ICs. Test noise is generated with an off-the-shelf radio RF/IF circuit. Wideband video amplifiers are not required. Typical performance figures include pulse widths from 50 ns, target ranges from 0 to ambiguity maximum, target velocities from 0.5 m/s to 500 m/s and PRFs up to 100 kflz. Virtual target RCS can be adjusted as needed in a straightforward way.     

Image texture synthesis-by-analysis using moving-average models

A synthesis-by-analysis model for texture replication or simulation is presented. This model can closely replicate a given textured image or produce another image that although distinct from the original, has the same general visual characteristics and the same first and second-order gray-level statistics as the original image. The texture synthesis algorithm, proposed contains three distinct components: a moving-average (MA) filter, a filter excitation function, and a gray-level histogram. The analysis portion of the texture synthesis algorithm derives the three from a given image. The synthesis portion convolves the MA filter kernel with the excitation function, adds noise, and modifies the histogram of the result. The advantages of this texture model over others include conceptually and computationally simple and robust parameter estimation, inherent stability, parsimony in the number of parameters, and synthesis through convolution. The authors describe a procedure for deriving the correct MA kernel using a signal enhancement algorithm, demonstrate the effectiveness of the model by using it to mimic several diverse textured images, discuss its applicability to the problem of infrared background simulation, and include detailed algorithms for the implementation of the model     

Market-based systems for instrument development and science planning

Market-based systems are those systems in which currency is used to express demand for a limited resource. In these systems, users `own' currency and exchange it for a desired commodity. Though used for thousands of years, market-based applications to space missions are still in their infancy. The first successful application was in 1992 with the Cassini Mission to Saturn. In this case, the sum total of mass and dollars for the science instruments had to fit within the allocated resource envelope. Results from the use of a market-based system show that the entire science payload grew from original estimates by only +1% for cost, and by –7% for mass. The next application was for Space Shuttle Secondary Payloads. In this application, available shuttle lift mass, number of lockers for secondary payloads, and available astronaut time had to be allocated between 5 NASA Users. Experiments showed that a market-based system can reduce the size of the required workforce needed to produce a manifest of the same quality as one produced `by committee.' Finally, a market-based system was experimentally applied to LightSAR science planning, a proposed joint NASA/Commercial RADAR mission. In this application, users were able to produce a conflict-free timeline of events remotely, of high science value, in about half the time required by more traditional methods.     

A two-dimensional position-sensitive spectroscopic proportional counter for balloon-borne hard X-ray astronomy

A new design of position sensitive spectroscopic proportional counter is described, for use in a balloon borne hard x-ray telescope. Initial position and spectral resolution data from a one-dimensional laboratory prototype are reported. With this device, the final telescope will have an angular resolution of better than 10 minutes of arc.     

Preliminary results of Cytos 2 experiment.

Cytos 2 experiment, carried out during the French-Soviet manned flight (July 1982), has studied the antibiotics sensitivity of bacteria cultivated in vitro during the orbital flight. The results show an increase of the antibiotics resistance and a larger thickness of the cellular envelope for the inflight cells. The increase of antibiotics resistance can be related to a stimulating effect of space on the cell growth rate or to changes of the cellular envelope structure.