Low observable target motion analysis using amplitude information

In conventional passive and active sonar system, target amplitude information (AI) at the output of the signal processor is used only to declare detections and provide measurements. We show that the AI can be used in passive sonar system, with or without frequency measurements, in the estimation process itself to enhance the performance in the presence of clutter where the target-originated measurements cannot be identified with certainty, i.e., for “low observable” or “dim” (low signal-to-noise ratio (SNR)) targets. A probabilistic data association (PDA) based maximum likelihood (ML) estimator for target motion analysis (TMA) that uses amplitude information is derived. A track formation algorithm and the Cramer-Rao lower bound (CRLB) in the presence of false measurements, which is met by the estimator even under low SNR conditions, are also given. The CRLB is met by the proposed estimator even at 6 dB in a cell (which corresponds to 0 dB for 1 Hz bandwidth in the case of a 0.25 Hz frequency cell) whereas the estimator without AI works only down to 9 dB. Results demonstrate improved accuracy and superior global convergence when compared with the estimator without AI. The same methodology can be used for bistatic radar     

A study of biohazard protection for farming modules of lunar base CELSS.

For the Closed Ecological Life Support System (CELSS) of a manned lunar base which is planned to be built on the moon early in the 21st century, several proposed programs exist to grow vegetables inside a farming module. At the 40th IAF (Malaga, 1989) the author et al presented a proposal for supplying food and nutrients to a crew of eight members, a basic concept which is based on growing four kinds of vegetables. This paper describes measures for biohazard protection in farming modules. In this study, biohazard protection means prevention of the dispersion of plant diseases to other plant species or other portions of farming beds.     

Vehicular Positioning System

There is a US Army vehicular positioning program under way called MAFIS (Mobile Automated Field Instrumentation System). Though its use is intended for full scale battlefield operational testing of mobile ground units and aircraft systems, the implications for extending this technology toward commercial aplications are the thrust of this paper.     

New nonlinear control algorithms for multiple robot arms

Multiple coordinated robot arms are modeled by considering the arms as closed kinematic chains and as a force-constrained mechanical system working on the same object simultaneously. In both formulations, a novel dynamic control method is discussed. It is based on feedback linearization and simultaneous output decoupling technique. By applying a nonlinear feedback and a nonlinear coordinate transformation, the complicated model of the multiple robot arms in either formulation is converted into a linear and output decoupled system. The linear system control theory and optimal control theory are used to design robust controllers in the task space. The first formulation has the advantage of automatically handling the coordination and load distribution among the robot arms. In the second formulation, it was found that by choosing a general output equation it became possible simultaneously to superimpose the position and velocity error feedback with the force-torque error feedback in the task space     

Deoxyribonucleoprotein structure and radiation injury: cellular radiosensitivity is determined by LET infinity -dependent DNA damage in hydrated deoxyribonucleoproteins and the extent of its repair.

For decades, theories of cellular radiosensitivity relied upon the initial patterns of energy deposition to explain radiation lethality. Such theories are unsound: cellular (DNA) repair also underlies cellular radiosensitivity. For the charged particles encountered in deep space, both the types of DNA damage caused in cellular deoxyribonucleoproteins and the efficacies of their repair are dependent on linear energy transfer (LET infinity), and repair efficiency is also influenced by cell and tissue type, i.e., the actual recovery processes involved. Therefore, quality factors derived from radiation quality alone are inadequate parameters for assessing the radiation risks of space flight. Until recently, OH radicals formed in bulk nuclear water were believed to be the major causes of DNA damage that results in cell death, especially for sparsely ionizing radiations. That hypothesis has now been challenged, if not refuted. Lethal genomic DNA damage is determined mainly by energy deposition in deoxyribonucleoproteins, and their hydration shells, and charge (energy) transfer processes within those structures.     

Lessons learned from the autonomous power system

The autonomous power system (APS) project at the NASA Lewis Research Center is described. The project is designed to demonstrate the applications of integrated intelligent diagnosis, control, and scheduling techniques to space power distribution systems. It consists of the autonomous power expert system (APEX) for fault detection, isolation, and recovery; the autonomous intelligent power scheduler, for efficient assignment of activity start times and resources; and power hardware (Brassboard) to emulate a space-based power system. Each part of the system was critiqued based on individual performance as well as the ability to interact with the other portions of the APS project. These critiques were used to determine guidelines for new and improved components     

Commercializing the International Space Station: current US thinking

This article provides an overview of NASA's plans to encourage commercial use of the International Space Station (ISS). It examines the reasons driving such commercialization and highlights those private companies currently most interested in undertaking profit-making operations on the station, as well as discussing those activities most likely to be seen as commercial possibilities. The steps NASA is taking to stimulate private interest are enumerated. Various unresolved issues are raised, such as the legal issues associated with commercial research, charging policy for in-orbit operations and ‘metering’ of in-orbit resources. It is noted that the international dimension of the ISS has thus far received little consideration in the USA.     

Operational communication systems and relationships to the ionosphere and space weather

There are a variety of operational communication systems that are dependent upon the ionosphere, and there are others that are influenced by the ionosphere. In the dependent category, we have short-wave (i.e., MF and HF systems) and long-wave systems (i.e., VLF and LF systems). In the influenced category we have some VHF systems such as meteor-burst systems, and higher frequency SATCOM systems in the UHF and SHF bands. The paper will address various resource management issues for specified operational systems, and the relationship with aspects of space-weather will be discussed. Some examples where space-weather information is used in existing systems are presented. We also identify how space-weather information could be used in those situations where it is currently unused. We conclude with challenges facing advocates of a viable space-weather program [Goodman, J.M. Space Weather and Telecommunications. Kluwer international series of Engineering and Computer Science, Springer Science + Buisness Media Inc., New York, 2005].     

Protein crystal growth aboard the U.S. space shuttle flights STS-31 and STS-32.

The first microgravity protein crystal growth experiments were performed on Spacelab I by Littke and John. These experiments indicated that the space grown crystals, which were obtained using a liquid-liquid diffusion system, were larger than crystals obtained by the same experimental system on earth. Subsequent experiments were performed by other investigators on a series of space shuttle missions from 1985 through 1990. The results from two of these shuttle flights (STS-26 and STS-29) have been described previously. The results from these missions indicated that the microgravity grown crystals for a number of different proteins were larger, displayed more uniform morphologies, and yielded diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth. This paper presents the results obtained from shuttle flight STS-32 (flown in January, 1990) and preliminary results from the most recent shuttle flight, STS-31 (flown in April, 1990).