Comments, with reply, on `Status of CR-like lower bounds fornonlinear filtering' by T.H. Kerr

The commenters object to criticisms of their work that appeared in the above-titled paper (ibid., vol.25, no.5, p.590-601, Sept. 1989) and provide a defense of their results. The author presents further arguments to buttress his claims     

A fusion and learning algorithm for landing aircraft tracking:compensating for exhaust plume disturbance

An algorithm is presented for tracking a landing aircraft using fusion of two different passive sensors, a laser range finder (LRF) and a forward-looking infrared (FLIR) camera. The main feature of this algorithm is its ability to identify and compensate for an exhaust plume disturbance. The algorithm is based on the extended Kalman filter (EKF) and the filtering confidence function (FCF) which introduces a learning approach to the tracking problem. The results of a simulation using the learning tracking algorithm and the EKF alone are presented and compared     

Dust hazard near Halley Comet in case of the VEGA project

The motion of dust particles near Halley Comet is studied and the probability of dust impacts with the spacecraft in case of the VEGA (Venus-Halley)- project is determined. The formation of a crater due to a particle impact with the dust shield is considered and the necessity for using a dual-sheet bumper shield is substantiated. The thickness of a front sheet that plays a role of the particle evaporator is estimated theoretically. The numerical experiment is carried out that simulates the dynamics of collision and evaporation of a particle. Three factors causing perforations of the rear sheet are discussed, i.e. dust penetrated through holes in the front sheet, gas jets and spall fragments of the front-sheet. The consideration of these factors makes it possible to estimate basic parameters of the dual-sheet bumper shield. Flexural vibrations of the front sheet under action of the reverse gaseous jet from the rear sheet are discussed that can affect essentially the shield strength. The perturbing effect of the dust and gas fluxes on the spacecraft is studied.     

New progress on space solar telescope

The design of the Space Solar Telescope (phase B) has been completed. The telescope system has been manufactured (phase C) since the beginning of 1999, and it will be assembled by the end of 2000. In this paper, mainly the optical design, technique and manufacture will be described. The launch is planned for the summer of 2004.     

Book reviews

The general significance of streamers of the solar corona is discussed in the frame of our knowledge of the solar wind phenomenon and the large-scale solar magnetic structure. Thermodynamical and geometric parameters of streamers observed and measured at total solar eclipses are reviewed. Both the low part (in the form of a helmet with a cusp) and the external part (in the form of a stalk extended at many solar radii) are considered. The modelling of streamers starts with the analysis of effects produced by the solar wind flow on a magnetic structure. Facts and arguments are presented in favor of a model with a current sheet and reconnection processes going on along the axis of the streamer, especially in the non-collisional part of the radially extended streamer. Further development of the Pneuman and Kopp (1971) model is discussed, including difficulties occurring in the interpretation of a stationary solution. An empirical model satisfying observations is presented. Future researchs on streamers were discussed with emphasis on observations to be done with the space-borne coronagraphs on the SOHO spacecraft.     

HXMT satellite for space hard X-ray observation

In this paper, the Hard X-ray Modulation Telescope mission is introduced. Its primary objective is to perform the hard X-ray all sky survey of high resolution and high sensitivity. The expected angular resolution and position accuracy of the satellite are better than 10^′ and 2^′, respectively. The preliminary mission design is analyzed. And a new attitude subsystem scheme is presented to meet the high precision demand of attitude determination. A conclusion is drawn that the mission design is feasible. The possible launch of it will significantly advance the astrophysical study.     

High resolution imaging of objects at Ka band

A coherent wideband millimeter wave (mmW) imaging radar which operates in two different imaging modes is briefly described. The principles of two-dimensional (2-D) high resolution imaging are introduced. The image reconstruction algorithm together with image enhancement techniques are discussed. Some experiments imaging on both scaled aircraft model and full-size large scale vehicle are presented     

Chemical studies on the possible existence of life on Mars.

Although there is no direct evidence yet for the existence of life on Mars, it is reasonable to conclude that the emergence of life on Earth, which appears to have been controlled by universal laws of physics and chemistry, may have been repeated elsewhere in the universe. The dual approach of synthesis and analysis in our experimental studies has provided ample evidence in support of this hypothesis.     

Adaptive array CFAR detection

Presented here is a large class of adaptive array detection algorithms with constant false alarm rate (CFAR), so that the false alarm rate can be set to any preassigned number without knowledge of the noise covariance matrix. This class map incorporate any usual method of cell averaging and any method for array weight vector synthesis. A sufficient condition for CFAR is derived, which is easy to satisfy in practice. Basic system parameters are discussed. An example of detection performance for a simple cell-averaging detector, in which the array weight vector is synthesized by the method of diagonal loading, is provided using Monte Carlo simulations