Recursive mode star identification algorithms

Star identification can be accomplished by several different available algorithms that identify the stars observed by a star tracker. However, efficiency and reliability remain key issues and the availability of new active pixel cameras requires new approaches. Two novel algorithms for recursive mode star identification are presented here. The first approach is derived by the spherical polygon search (SP-search) algorithm, it was used to access all the cataloged stars observed by the sensor field-of-view (FOV) and recursively add/remove candidate cataloged stars according to the predicted image motion induced by camera attitude dynamics. Star identification is then accomplished by a star pattern matching technique which identifies the observed stars in the reference catalog. The second method uses star neighborhood information and a catalog neighborhood pointer matrix to access the star catalog. In the recursive star identification process, and under the assumption of "slow" attitude dynamics, only the stars in the neighborhood of previously identified stars are considered for star identification in the succeeding frames. Numerical tests are performed to validate the absolute and relative efficiency of the proposed methods.     

Electromechanical Actuation Technology for the All-Electric Aircraft

Electromechanical actuation is a critical element that must be developed and verified to make the all-electric aircraft a viable concept. For several years the Flight Control Division of the Air Force Wright Aeronautical Laboratories has sponsored activities to demonstrate the credibility of electromechanical actuation systems (EMAS) for primary flight control actuation functions. The foundation for these EMAS activities and several electromechanical actuation development programs are described here. One involves the design, fabrication, and laboratory test of a rotary, hingeline electromechanical actuator. Another involves the development and flight test demonstration of a linear electromechanical actuator for controlling an aileron of a C-141 aircraft. A third involves the design and development of a linear electromechanical actuator for missiles having severe performance, temperature, and volumetric requirements. In addition, a brief summary of the results from two aircraft actuation trade studies compare the baseline (conventional) hydraulic flight control system with an all-electric airplane concept including quantitative comparisons of weight, reliability and maintainability, and life cycle costs.     

State Estimation and Divergence Analysis

A growing memory discrete dynamic model for performing temporal extrapolations along a predetermined path in a random field is presented. This dynamic model is used to drive a linear system that is itself driven by discrete white noise. The coupled system is used to derive a state estimation scheme that recursively processes noisy measurements of the system. In addition, using the aforementioned dynamic model as a reference (truth) model, the authors develop a covariance analysis to measure the estimation errors that occur when the dynamics along the path through the field are modeled as a Markov linear model and state estimation is performed using discrete Kalman filtering. The performance evaluation of an inertial navigation system influenced by the Earth's gravity field aboard a maneuvering ship is provided as a specific illustrative example.     

On-Line Computer for Transient Turbine Cascade Instrumentation

A 32-channel computer based data acquisition and processing system em has been developed for use with the new type of transient cascade facility at Oxford. This is used for testing turbine blades and nozzle guide vanes at full-scale engine Reynolds and Mach numbers ers with correct wallto-flow temperature ratios. A novel technique for processing transient heat transfer data from thin film surface resistance thermometers has been developed. Measurements of surface ace pressure around blades, and of the upstream turbulence level have been made. The cascade and instrumentation are shown to have advantages both in cost and effectiveness over continuous running cascades.     

9. The venus ionosphere and solar wind interaction

The current state of knowledge of the chemistry, dynamics and energetics of the upper atmosphere and ionosphere of Venus is reviewed together with the nature of the solar wind-Venus interaction. Because of the weak, though perhaps not negligible, intrinsic magnetic field of Venus, the mutual effects between these regions are probably strong and unique in the solar system. The ability of the Pioneer Venus Bus and Orbiter experiments to provide the required data to answer the questions outstanding is discussed in detail.     

Ground Testing of Inertial Navigators to Improve Dynamic Performance

A ground testing method has been devised to evaluate the dynamic errors of an inertial navigation system. A trimmed stationary inertial system in the navigation mode can be subjected to programmed platform orm drift rates, and generate position outputs which are compared with those of a perfect navigator. The linearized error equations for this testing mode are derived and the resulting position error propagation is analyzed using Kalman filtering in order to identify the error sources. A simulated platform with a fixed set of error sources is analyzed to evaluate this testing concept. An example is presented to show that the gyro and accelerometer scale factor and misalignment error coefficients can be estimated.     

An exact expression for resolution cell area in special case ofbistatic radar systems

An exact expression for the bistatic resolution-cell area (A _B) is developed for the special case in which either the transmit or receive antenna has a broad azimuth beamwidth or is omnidirectional. Quantitative examples are presented to illustrate the variation of A_B with location. A comparison is made with the performance of a commonly used approximation formula     

Radar Target Detection and Map-Matching Algorithm Studies

Results of a study of adaptive threshold target detection and map-matching algorithms are presented. Log threshold processing is shown to be preferred over linear threshold processing when the clutter data surrounding the target cell is contaminated by other targets, decoy corner reflectors, or bright clutter cells. Whereas previous studies have resorted to extensive Monte-Carlo simulations of log threshold algorithms, the results were obtained using a novel analytical approach based upon Parseval's theorem.