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     

Numerical modelling of radiance of the presumed dust torus around Mars in the 0.350-1 μm spectral range

Currently conducted studies on modelling of scattered solar radiation in the 0.350-1.00 μm range along the Phobos orbit around Mars are presented. Our calculations include various types of grains, various densities and scattering angles. The calculations are performed with the aid of LOWTRAN7 program. These studies are directly related to the photometer coupled to PFS (Planetary Fourier Spectrometer) planned for the Mars-96 mission.     

Measuring the matter distribution within z = 0.2 cluster lenses with XMM-Newton

We present an analysis of seven clusters observed by XMM-Newton as part of our survey of 17 most X-ray luminous clusters of galaxies at z  0.2 selected for a comprehensive and unbiased study of the mass distribution in massive clusters. Using the public software FTOOLS and XMMSAS we have set up an automated pipeline to reduce the EPIC MOS and pn spectro-imaging data, optimized for extended sources analysis. We also developped a code to perform intensive spectral and imaging analysis particularly focussing on proper background estimate and removal. XMM-Newton deep spectro-imaging of these clusters allowed us to fit a standard β-model to their gas emission profiles as well as a standard MEKAL emission model to their extracted spectra, and test their inferred characteristics against already calibrated relations.     

Radar target classification of commercial aircraft

With the increased availability of coherent wideband radars there has been a renewed interest in radar target recognition. A large bandwidth gives high resolution in range which means target discrimination may be possible. Coherence makes cross-range resolution and radar images possible. Some of the problems of classifying high resolution range profiles (HRRPs) are examined and simple preprocessing techniques which may aid subsequent target classification are investigated. These techniques are applied to HRRP data acquired at a local airport using the Microwave Radar Division (MRD) mobile radar facility It is found that Boeing 727 and Boeing 737 aircraft can be reliably distinguished over a range of aspect angles. This augers well for future target classification studies using HRRPs     

On adaptive multiband signal detection with the SMI algorithm

In a nonstationary and/or nonhomogeneous interference environment, an adaptive system for target detection may suffer a severe performance degradation due to the lack of a sufficient amount of data from which the system can learn (estimate) the statistics of the environment. The detection performance of an adaptive system, which employs a frequency diversity (multiband) signaling waveform and a multiband sample matrix inversion algorithm (SMI), is analyzed. By comparison with the corresponding single-band system under the chosen system constraint, it is shown that the multiband system can significantly outperform the single band when the amount of data available from a single frequency band is severely limited by the environment     

Late Stages of Stellar Evolution

A large fraction of ISO observing time was used to study the late stages of stellar evolution. Many molecular and solid state features, including crystalline silicates and the rotational lines of water vapour, were detected for the first time in the spectra of (post-)Asymptotic Giant Branch (AGB) stars. Their analysis has greatly improved our knowledge of stellar atmospheres and circumstellar environments. A surprising number of objects, particularly young planetary nebulae with Wolf-Rayet (WR) central stars, were found to exhibit emission features in their ISO spectra that are characteristic of both oxygen-rich and carbon-rich dust species, while far-IR observations of the PDR around NGC 7027 led to the first detections of the rotational line spectra of CH and CH⁺. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA.     

Differential flank growth.

With the mathematical basis for the precise analysis of developmental processes in plants, the patterns of growth in phototropic and gravitropic responses have become better understood. A detailed temporal and spatial quantification of a growth process is an important tool for evaluating hypotheses about the underlying physiological mechanisms. Studies of growth rates and curvature show that the original Cholodny-Went hypothesis cannot explain the complex growth patterns during tropic responses of shoots and roots. In addition, regulating factors other than the lateral redistribution of hormones must be taken into account. Electrophysiological studies on roots led to a modification of the Cholodny-Went hypothesis in that redistributions of bioelectrical activities are observed.     

A method for improving extended Kalman filter performance forangle-only passive ranging

A relatively simple method is presented which eliminates previously reported (Oct. 1985) erratic estimation performance associated with Cartesian formulations of the extended Kalman filter (EKF) for the 2D angle-only emitter location problem. The technique is based on an initialization procedure which combines a priori probability density function (pdf) information with single measurement a posteriori pdf information in a manner which is more efficient than the EKF. Simulation results are presented which demonstrate the utility of the technique as compared with a previously offered modified gain EKF