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.     

Enhanced resolution in simple radars

Many simple radars use fact-risetime pulses, but wide bandwidth does not translate into corresponding high resolution since the spectrum is far from flat. A scheme for enhancing down- and cross-range resolution of multiple targets through a two-step partial equalization of the spectrum is illustrated by detailed computer simulation, with emphasis on the tradeoffs between resolution and signal-to-noise ratios. Three examples are treated: two equal scattering centers, two unequal scattering centers, and compound target     

On Relationship of Flow Swirl Parameters and Gas-Dynamic Efficiency of Gas Turbine Engine Interturbine Transition Duct

The paper highlights significance of the interturbine transition duct as part of the high pressure and low pressure turbine spool. The correlations have been suggested allowing us to estimate variation of the average cross section flow swirl while its passing the interturbine transition duct.     

Covariance matrix estimation for adaptive CFAR detection incompound-Gaussian clutter

We address the estimation of the structure of the covariance matrix and its application to adaptive radar detection of coherent pulse trains in clutter-dominated disturbance modeled as a compound-Gaussian process. For estimation purposes we resort to range cells in spatial proximity with that under test and assume that these cells, free of signal components, can be clustered into groups of data with one and the same value of the texture. We prove that, plugging the proposed estimator of the structure of the covariance matrix into a previously derived detector, based upon the generalized likelihood ratio test (GLRT), leads to an adaptive detector which ensures the constant false alarm rate (CFAR) property with respect to the clutter covariance matrix as well as the statistics of the texture. Finally, we show that this adaptive receiver has an acceptable loss with respect to its nonadaptive counterpart in cases of relevant interest for radar applications     

Automated air defense system using knowledge-based system

The proposed KAAD (knowledge-based automated air defense) system demonstrates a man-machine environment for airspace defense systems. When the unknown aircraft is hostile, a threat rating and response methods are generated by the system. It serves as a double-check decision-making system for a war control center. In addition to this application, the KAAD system can also be a useful tool as a training program for the war controller. The capabilities of the system are limited due to the shortage of knowledge resources. It requires communications among war controllers and air fighter pilots to organize a practical knowledge base. It is shown that the KAAD system can be combined with an automated ATC (air traffic control) system to become a practical system for air defense applications     

The IMPACT Solar Wind Electron Analyzer (SWEA)

SWEA, the solar wind electron analyzers that are part of the IMPACT in situ investigation for the STEREO mission, are described. They are identical on each of the two spacecraft. Both are designed to provide detailed measurements of interplanetary electron distribution functions in the energy range 1～3000 eV and in a 120°×360° solid angle sector. This energy range covers the core or thermal solar wind plasma electrons, and the suprathermal halo electrons including the field-aligned heat flux or strahl used to diagnose the interplanetary magnetic field topology. The potential of each analyzer will be varied in order to maintain their energy resolution for spacecraft potentials comparable to the solar wind thermal electron energies. Calibrations have been performed that show the performance of the devices are in good agreement with calculations and will allow precise diagnostics of all of the interplanetary electron populations at the two STEREO spacecraft locations.     

Comparison of ≳40 keV Electron Events at High and Low Heliolatitudes: Ulysses/HI-SCALE and ACE/EPAM

We have performed a joint survey of anisotropic ≳40 keV electron events from August 1997 to September 2000 using the matched detectors on the Ulysses (ULS)/HI-SCALE and the ACE/EPAM instruments. A computer algorithm selected events with strong, statistically significant pitch-angle anisotropies. Electron pitch-angle distributions at ACE (∼1 AU) are often ‘beams’ that are strongly collimated along the local interplanetary magnetic field (IMF). These flare-associated impulsive injections can display rapid rise times (∼15 min) and slower decays, or more irregular intensity histories. At ULS, the electron intensities are lower and the time histories smoother, but strong anisotropies are still observable, indicating direct, nearly field-aligned propagation outward from the Sun. We focus on four event periods, selected from the survey, during times when the angle between the footpoints of the IMF lines intersecting ACE and ULS is small. These events span three full years and cover a wide range of distances and heliographic latitudes. We found one reasonably good association between impulsive electron events at ACE and ULS, and two events with small field-aligned gradients. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comments with reply, on `A new look at nonseparable syntheticaperture radar processing' by A. Di Cenzo

The commenters point out that the idea using a two-dimensional digital correlation technique to perform synthetic-aperture-radar (SAR) processing, presented as new in the above-titled paper (see ibid., vol.24, p.218-23, May 1988), was described by them as early as 1978 and has since been described by other authors. They discuss some of these earlier studies. The author replies that he was unaware of the earlier work, and that he did not intend to convey the impression that the nonseparable transform domain processor that he presented was the first     

The role of soil science in space exploration

New frontiers in soil science are currently found in the investigation of soils in harsh, terrestrial and simulated extraterrestrial environments, the development of new methods and probes for soil characterization, and the eventual investigation, characterization, and development of extraterrestrial soil. Current aspects of space science involving soil studies are presented, including a more detailed soil study program involving the microflora of desert soil ecosystems. Basic precepts are given for preparation, investigation, and use of extraterrestrial soil.Contribution from the Bioscience Group of the Chemistry Section, Space Science Division, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California. Presented as an invitational paper before the Synapsis Club, University of California, Riverside, California, December 3, 1962.     

Nonlinear bending-torsion flutter experiments of a medium-aspect-ratio flexible wing model

In this research a two-motion medium-aspect-ratio straight flexible wing model was tested. Tests with the wing model were conducted in the subsonic wind tunnel of the Faculty of Aerospace Engineering at the Technion, Israel. Experimental results obtained for flutter and Limit Cycle Oscillations (LCO) of the wing model are presented. At least two types of flutter and postflutter LCO have been observed. Both types were characterized by coupling between the torsional and bending modes. The first type flutter was associated with coupling of the first bending and first torsional modes, whereas the second type was observed for coupling of the first torsional and second bending modes.