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     

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     

Nonlinear Estimation of Generalized Vector Shot Processes

A class of nonlinear filters for dynamical systems driven by generalized Poisson processes is developed. One of the filters, the maximum a posteriori (MAP) filter, is shown by a numerical example to be superior to other known predictors in getting the highest target hit probabilities, and it is relatively simple to implement. This filter has applications in both fire control and air traffic control of maneuvering piloted vehicles.     

Short-term and long-term clinostat and vibration-induced biochemical changes in dwarf marigold stems.

Stems of 21-day dwarf Marigold plants cultivated on the clinostat were compared with plants cultivated on vertical axis rotators ("vibrational controls") and stationary controls for long-term changes in cell wall composition. Stems of 21-day plants grown under stationary conditions and subsequently exposed to the clinostat for 24 hours were also analyzed. Among the long-tern markers, calciun, lignin, and protein-bound hemicellulose (possibly cell wall glycoprotein) clearly differentiated the effects of vibration from those of the clinostat. Short-term differential responses included rate of ethylene production, nastic movement and peroxidase activity of the cell wall, but not of the protoplast.     

The Halley dust model

The properties of dust ejecta from Comet Halley are studied on the basis of (a) evidence from the comet's past apparitions and (b) analogy with recent, physically similar comets. Specifically discussed are the light curve and spectrum, discrete phenomena in the head, the physical properties of the nucleus (size, albedo, rotation, surface temperature, and morphology), and an interaction between the nucleus and dust atmosphere. Also reviewed are constraints on the size and mass distributions of dust particles, information on submicron-size and submillimeter-size grains from the comet's dust tail and antitail, and the apparent existence of more than one particle type. Similarities between the jet patterns of Halley and the parent comet of the Perseid meteor stream are depicted, and effects of the surface heterogeneity (discrete active regions) on the dust flow are assessed. Current dust models for Halley are summarized and the existence of short-term variations in the dust content in the comet's atmosphere is suggested.     

Molecular diversity of cyanobacteria inhabiting coniform structures and surrounding mat in a Yellowstone hot spring

Lithified coniform structures are common within cyanobacterial mats in Yellowstone National Park hot springs. It is unknown whether these structures and the mats from which they develop are inhabited by the same cyanobacterial populations. Denaturing gradient gel electrophoresis and sequencing and phylogenetic analysis of 16S rDNA was used to determine whether (1) three different morphological types of lithified coniform structures are inhabited by different cyanobacterial species, (2) these species are partitioned along a vertical gradient of these structures, and (3) lithified and non-lithified sections of mat are inhabited by different cyanobacterial species. Our results, based on multiple samplings, indicate that the cyanobacterial community compositions in the three lithified morphological types were identical and lacked any vertical differentiation. However, lithified and non-lithified portions of the same mat were inhabited by distinct and different populations of cyanobacteria. Cyanobacteria inhabiting lithified structures included at least one undefined Oscillatorialean taxon, which may represent the dominant cyanobacteria genus in lithified coniform stromatolites, Phormidium, three Synechococcus-like species, and two unknown cyanobacterial taxa. In contrast, the surrounding mats contained four closely related Synechococcus-like species. Our results indicate that the distribution of lithified coniform stromatolites may be dependent on the presence of one or more microorganisms, which are phylogenetically different from those inhabiting surrounding non-lithified mats.     

Increasing student learning through space life sciences education

Scientists and educators at Baylor College of Medicine are using space life sciences research areas as themes for middle school science and health instructional materials. This paper discusses study findings of the most recent unit, Food and Fitness, which teaches concepts related to energy and nutrition through guided inquiry. Results of a field test involving more than 750 students are reported. Use of the teaching materials resulted in significant knowledge gains by students as measured on a pre/post assessment administered by teachers. In addition, an analysis of the time spent by each teacher on each activity suggested that it is preferable to conduct all of the activities in the unit with students rather than allocating the same total amount of time on just a subset of the activities.     

Satellite measurements of cloud reflectance and optical thickness

We have computed the cloud reflectance and the optical thickness with the aid of atmospheric models from the first eleven months (April 1970 – February 1971) of Backscattered Ultraviolet (BUV) data over the pacific ocean. Both the cloud and the optical thickness are derived from the 380 nm channel by assuming that the entire IFOV (200 Km.) is filled by stratiform clouds. Our analysis show a large variability in the cloud reflectance in both the intertropic conversion zone (ITCZ) and the high latitudes. We also find that for 90% of the time in tropics, the clouds have optical thickness < 10. Our analysis of clouds with optical thickness between 10 and 20 show that in tropics the minimum frequency coincides with the dry zone at 2.5°s and the maximum frequency for clouds of optical thickness 10–20 is greater in summer than in winter and irrespective of the season, 50% of the time the clouds have optical thickness less than 13.     

Multi-channel improvements to satellite-derived global sea surface temperatures

High-quality multispectral measurements from satellites, and the recent development of multiple-window techniques to correct infrared brightness temperatures for atmospheric attenuation, have enabled marked improvements in global mapping of sea surface temperatures. The 4-km resolution data are in two visual bands and three atmospheric windows in the thermal infrared from the advanced Very High Resolution Radiometer (AVHRR) on NOAA's operational polar satellites. Various threshold and/or spatial homogeniety tests are applied to small data arrays to discriminate nominally cloud-free samples for subsequent processing. Tests of the multi-channel equations against independent buoy data gave bias = 0.42C and scatter = 0.62C. Global statistical comparisons with ships indicate significant improvements in accuracy and coverage over previous satellite-derived surface temperatures.