A prospectus for automatic target recognition

Aspects of autorecognition technology are discussed. The following topics are covered: The context and role of automatic target recognition (ATR), sensors and ATR systems, generic shape discrimination, countermeasures, and current capabilities. The authors conclude that the material supports a very favorable assessment of the power and importance of emerging ATR technology     

Who is who in Algol-land ?- Part I -

We computed the evolution through case A mass transfer for 8 systems with mass of the primary equal to 3 and 5 M₀, mass ratios 0.7 and 0.9, and different periods. To this we added similar results from Packet (1988) for M_i = 9 M₀, q_i = 0.6, P_i = 1.62 d.During the mass transfer two competing mechanisms in the gainer decide on the evolution of the system: the rejuvenation of this star as the increasing convective core mixes fresh hydrogen into the inner regions, and the acceleration of nuclear burning, responding to the increasing mass.In all the cases the net result is a faster decrease of the central hydrogen content compared to the mass losing star. The secondary fills its own critical Roche lobe and reversed mass transfer starts.From our results and those of Nakamura and Nakamura (1984), we find that reversed mass transfer occurs after core hydrogen burning of the secondary (case A₁B₂) approximately for periods larger than 1 d (M_1i = 3 M₀) to 2 d (M_1i = 13.4 M₀). For smaller periods this happens before the gainer ends its core hydrogen burning (case A₁A₂).     

Subcellular components of the amphibian egg: insights provided by gravitational studies.

Most cytoplasmic regions of fertilized amphibian eggs move with respect to the gravity vector in experimentally gravity oriented eggs. The pattern and extent of this movement varies among different batches of eggs. This variation in apparent cytoplasmic viscosity (or, conversely, cytoplasmic mobility) can be correlated with variations in subsequent morphogenesis of experimental, gravitationally manipulated eggs. Therefore, the proper interpretation of gravity experiments with amphibian eggs requires that one understand the subcellular basis for this variation on cytoplasmic mobility. Variation in the packing of the major cytoplasmic organelle, the yolk platelets, or the organization and amount of cytoskeletal components may explain the variation in cytoplasmic mobility. Evidence is presented that the variation in yolk volume density (fraction of total cytoplasmic volume occupied by yolk platelets) does not account for the variation in cytoplasmic mobility in Xenopus laevis eggs. Experimental evidence from cold-shocked inverted eggs indicates that microtubules may be involved in determining cytoplasmic mobility. However, quantitative evidence that the microtubule levels and state of the microtubules (polymerized vs. non-polymerized) in the whole Xenopus laevis egg does not correlate directly with cytoplasmic mobility is presented. The apparent conflict these data represent regarding the role of the cytoskeleton in determining cytoplasmic mobility is discussed.     

The effect of total solar eclipse of October 3, 2005, on the total electron content over Europe

GPS observations from EUREF permanent GPS network were used to observe the response of TEC (Total Electron Content) to the total solar eclipse on October 3, 2005, under quiet geomagnetic conditions of the daytime ionosphere. The effect of the eclipse was detected in diurnal variations and more distinctly in the variations of TEC along individual satellite passes. The trough-like variations with a gradual decrease and followed by an increase of TEC at the time of the eclipse were observed over a large region. The depression of TEC amounted to 3–4 TECU. The maximum depression was observed over all stations located at the maximum path of the solar eclipse. The delay of a minimum level of TEC with respect to the maximum phase of the eclipse was about 20–30 min.     

Non-LTE analysis of a new pulsating PG 1159-type central star detected in the ROSAT XRT all sky survey

We summarize the analysis of a new PG 1159 star, i.e., a hydrogen deficient pre-white dwarf detected in the ROSAT XRT all sky survey /1/. The X-ray source RX J2117.1+3412 is relatively faint (≈0.33 cnt s⁻¹) and was selected for optical identification on the basis of its extreme X-ray softness. With V = 13.2, the counterpart of the X-ray source is in the optical the second brightest member of the PG1159 class. CCD imagery reveals that the star is surrounded by an old highly excited planetary nebula of faint surface brightness. Optical line profiles of HeII, CIV, and OVI and the overall optical and ROSAT PSPC (0.1–2.4 keV) energy distributions are compared to predictions of NLTE model atmospheres. We find an excellent agreement between the atmospheric parameters derived from optical and soft X-ray data. The effective temperature of the star is extremely high (150,000 K). Abundances of He, C and O are found to be consistent with those derived in other PG1159 stars whereas the surface gravity is significantly smaller in RXJ2117.1+3412. New optical spectra presented here show the presence of ultra-high excitation lines of O VIII.     

Error Covariance Analysis of a Karhunen-Loeve Collocation Estimator

An error covariance analysis of a two-dimensional gravity compensation technique (KLC) employing a Karhunen-Loeve gravity disturbance model and the linear least-square collocation algorithm for its estimation is presented, without actually using any data. Its performance is compared with another gravity compensation technique (KLE), whose error covariance analysis was previously presented by Gupta. From the mismodeling analysis, KLC appears to be superior to KLE.     

Costas arrays with small number of cross-coincidences

A simple method is described for obtaining two or more Costas arrays with a maximum of one mutual bit or cross-coincidence, assuming that the vertical components of their relative shifts are appropriately bounded. The result can be useful for designing multiple Costas waveforms with small cross-ambiguities, if the potential Doppler shifts are restricted to a small portion of the waveform bandwidth     

A demonstration of sub meter GPS orbit determination and highprecision user positioning

High-accuracy orbits have been determined for satellites of the Global Positioning System (GPS), with submeter orbit accuracy demonstrated for two well-tracked satellites. Baselines of up to 2000 km in North America determined with the GPS orbits shows daily repeatability of 0.3-2 parts in 10⁸ and agree with very long baseline interferometry (VLBI) solutions at the level of 1.5 parts in 10 ⁸. Tests used to assess orbit accuracy include orbit repeatability from independent data sets, orbit prediction, ground baseline determination, and formal errors. One satellite tracked for eight hours each day shows RMS errors below 1 m even when predicted more than three days outside of a 1-week data arc. These results demonstrate the powerful relative positioning capability available from differential GPS tracking. Baselines have also been estimated between Florida and sites in the Caribbean region over 1000 km away, with daily repeatability of 1-4 parts in 10⁸. The best orbit estimation strategies included data arcs of 1-2 weeks, process noise models for tropospheric fluctuations, combined processing of GPS carrier phase and pseudorange data, and estimation of GPS solar pressure coefficients     

Integrated CIS VLF/Omega receiver design

The design of an integrated Russian-VLF/Omega receiver implemented on a TMS320C30-microprocessor-based SPECTRUM plug-in board installed in a PC-compatible portable computer is presented. The system also requires an external antenna, pre-amp, and frequency reference. The SPECTRUM board digitizes the RF signal to 16 b and then digitally mixes with the sines and cosines of the three Russian frequencies plus 10.2, 11-1/3, and 13.6 kHz. The mixer outputs are low-pass filtered, and the comb filters are implemented for the respective epochs. The computer accesses and processes the comb filter outputs, calculating and logging signal phase and amplitude. The design allows for easy future expansion to include unique and VLF communication frequencies