On state estimation for an orbiting single tether system

The effects of instrumentation accuracy and configuration on estimation error are studied for the small expandable-tether deployment system (SEDS) using a continuous-discrete extended Kalman filter (CDEKF) state estimator. A twelfth order model that incorporates the rigid body modes of the tether as well as the satellite attitude dynamics is developed. Simulation results using the model and the estimator indicate that the originally planned instrumentation package could not estimate the state vector adequately. Recommendations are made and results presented that reduce the estimation error by adding instruments and increasing selected measurement accuracies     

Further results on radar pointing error reduction using discreteextended Kalman filtering

A recently proposed method of reducing target glint errors in radar systems using extended Kalman filtering is further extended with the inclusion of and compensation for clutter effects. A discrete target model and discrete Kalman filter (DKF) are used. Simulation results demonstrating the DKF are presented, and the limits on the effectiveness of the method are investigated. The major advantage of the DKF is that it can be implemented in software in the digital processor of the radar, offering flexibility over continuous time filters. The ability of the filter to reduce clutter effects further demonstrates the usefulness of this technique for radar pointing error reduction     

Radar Target Pointing Error Reduction Using Extended Kalman Filtering

A new method of reducing target glint errors in radar systems is presented. The target is modeled as n reflectors whose magnitudes and phases are known. The reflector positions are described by a dynamical model driven by white Gaussian noise. The resulting vibrations of the target reflectors produce glintlike pointing errors in the radar system. An extended Kalman filter is developed to estimate the positions of the target reflectors; this information is used to substantially reduce the pointing error due to glint. Data illustrating this glint reduction is given. The model is extended by the inclusion of clutter effects modeled in the same fashion as the glint phenomenon. The results presented indicate the limits of usefulness of this technique as a function of both receiver noise and relative clutter amplitude.     

Real time estimator for control of an orbiting single tether system

A real-time estimator is developed for the control of the Tether Dynamics Explorer (TDE) system. TDE is being used in a series of tethered satellite flight experiments whose purpose is to validate existing system models and test proposed control laws. Each experiment consists of an orbiting Delta II second stage which deploys toward the Earth a small box-shaped passive endbody at the end of a flexible tether. A discrete extended Kalman filter (DEKF) is presented which can operate in real time and in conjunction with control laws. This filter estimates the in-plane and out-of-plane tether libration angles and their rates from a proposed three-axis tether tension measurement device in the Delta second stage. The simulation results indicate that the DEKF can estimate the libration angle and their rates from a three-axis tension and length measurement with an acceptable error. The relatively simple computations required make this algorithm particularly well suited for real-time operation.<>     

Wearable computers open a new era in support resource management

Our aerospace customers are demanding that we drastically reduce the operating and support costs of our products. In today's aerospace maintenance environment, the vast majority of maintenance technicians are using paper technical publications, with fixed troubleshooting trees, and manual or semi-automated post maintenance documentation. Interactive Electronic Technical Manuals (IETMs) are at this time being deployed with portable maintenance aids, often an electronic notebook-sized data presentation system, some with expert system based troubleshooting aids. Many of the IETM based systems still require post maintenance documentation and, the maintenance control function is at best, updated when each maintenance task is completed and the vehicle departs. Advances in wearable computer technologies allow us to integrate the maintenance technician with a highly automated, tightly managed support system that will significantly reduce support costs and turn-around times while improving the quality of maintenance. A “Portable Maintenance Terminal” is a wearable computer configured to meet a maintenance technician's information and communication needs. The Portable Maintenance Terminal (PMT) will place the maintenance technician in the loop with the support system. Wearable computers are intended for use in locations where easy access to a desktop computer or laptop is not practical, or where operators are required to have their hands on the job rather than being busy with a computer. The wearable PMT can provide a hands-free, heads-up, networked computing environment     

Sociotechnical Systems Evolution and International Stability: 1885-2001

A number of evolutionary sociotechnical patterns associated with the intensification of warfare and movement of the international system into a domain far from equilibrium are discussed. Evolution is extended from the past 100 years to the end of the 20th century with the identification of several likely crises precipitatory to World War III. Systems theoretic interpretation of a number of evolutionary developments is made. The use of systems concepts and systems experts in the management of international stability is discussed further.     

Discrete extended Kalman filter for radar point error reduction

A recently proposed method of reducing target glint errors in radar systems is further enhanced with the development of a discrete target model and discrete Kalman filter (DKF). Simulation results demonstrating the DKF are presented, and the limits of the usefulness of this method are investigated. The major advantage of the DKF is that it can be implemented in software in the digital processor of the radar offering flexibility over continuous-time filters     

Significance of rhizosphere microorganisms in reclaiming water in a CELSS.

Plant-microbe interactions, such as those of the rhizosphere, may be ideally suited for recycling water in a Controlled Ecological Life Support System (CELSS). The primary contaminant of waste hygiene water will be surfactants or soaps. We identified changes in the microbial ecology in the rhizosphere of hydroponical1y grown lettuce during exposure to surfactant. Six week old lettuce plants were transferred into a chamber with a recirculating hydroponic system. Microbial density and population composition were determined for the nutrient solution prior to introduction of plants and then again with plants prior to surfactant addition. The surfactant Igepon was added to the recirculating nutrient solution to a final concentration of 1.0 g L-1. Bacteria density and species diversity of the solution were monitored over a 72-h period following introduction of Igepon. Nine distinct bacterial types were identified in the rhisosphere; three species accounted for 87% of the normal rhizosphere population. Microbial cell number increased in the presence of Igepon, however species diversity declined. At the point when Igepon was degraded from solution, diversity was reduced to only two species. Igepon was found to be degraded directly by only one species found in the rhizosphere. Since surfactants are degraded from the waste hygiene water within 24 h, the potential for using rhizosphere bacteria as a waste processor in a CELSS is promising.