Ionization effect of solar protons in the Earth atmosphere – Case study of the 20 January 2005 SEP event

The cosmic ray ground level enhancement on January 20, 2005 is among the largest recorded events in the history of cosmic ray measurements. The solar protons of MeV energies cause an excess of ionization in the atmosphere, specifically over polar caps following major solar disturbances. The ionization effect in the Earth atmosphere is obtained for various latitudes on the basis of solar proton energy spectra, reconstructed from GOES 11 measurements and subsequent full Monte Carlo simulation of cosmic ray induced atmospheric cascade. The estimation of ionization rates is based on a numerical model for cosmic ray induced ionization. The evolution of atmospheric cascade is performed with the CORSIKA 6.52 code using FLUKA 2006b and QGSJET II hadron interaction models. The atmospheric ion rate ionization is explicitly obtained for 40°N, 60°N and 80°N latitudes. The time evolution of obtained ion rates is presented. It is demonstrated that ionization effect is negative for 40°N and small for 60°N, because of accompanying Forbush decrease. The ionization effect is significant only in sub-polar and polar atmosphere during the major ground level enhancement of 20 January 2005.     

Radiative and hybrid cooling of infrared space telescopes

The designs of cold space telescopes, cryogenic and radiatively cooled, are similar in most elements and both benefit from orbits distant from the Earth. In particular such orbits allow the anti-sunward side of radiatively-cooled spacecraft to be used to provide large cooling radiators for the individual radiation shields. Designs incorporating these features have predictedT _tel near 20 K. The attainability of such temperatures is supported by limited practical experience (IRAS, COBE). Supplementary cooling systems (cryogens, mechanical coolers) can be advantageously combined with radiative cooling in hybrid designs to provide robustness against deterioration and yet lower temperatures for detectors, instruments, and even the whole telescope. The possibility of such major additional gains is illustrated by the Very Cold Telescope option under study forEdison, which should offerT _tel5 K for a little extra mechanical cooling capacity.     

An approach to knowledge-aided covariance estimation

This paper introduces a parametric covariance estimation scheme for use with space-time adaptive processing (STAP) methods operating in heterogeneous clutter environments. The approach blends both a priori knowledge and data observations within a parameterized model to capture instantaneous characteristics of the cell under test (CUT) and reduce covariance errors leading to detection performance loss. We justify this method using both measured and synthetic data. Performance potential for the specific operating conditions examined herein include: 1) averaged behavior within roughly 2 dB of the optimal filter, 2) 1 dB improvement in exceedance characteristic relative to the optimal filter, highlighting improved instantaneous capability, and 3) impervious ness to corruptive target-like signals in the secondary data (no additional signal-to-interference-plus-noise ratio (SINK) loss, compared with 10 dB or greater loss for the standard STAP implementation), with corresponding detections comparable to the optimal filter case     

Interaction onde de choc-couche limite laminaire sur un corps de revolution en rotation

(Shock Wave-Laminar Boundary Layer Interaction on a Spinning Axisymmetric Body)—A method is developed to predict the shock wave-laminar boundary layer interaction on an axisymmetric body spinning in axial flow. The integral scheme of Lees, Reeves and Klineberg is used. The Falkner Skan “type” equations is then established for the boundary layer on spinning cylinder and used to construct the polynomial representation of the integral quantities. The independence of the polynomials with respect to the spinning rate is demonstrated. A cylinder of 200 mm diameter with a flare is built and tested up to 5000 rmp in wind tunnel at M = 2.21. The pressure measurements are in good agreement with the theoretical results. The rotation induces the decreasing of the pressure level and boundary layer separation inside the interaction region.     

Signal transduction in T lymphocytes--a comparison of the data from space, the free fall machine and the random positioning machine.

In this paper we discuss the effect of microgravity on T cells and we present the data of studies with two new machines for 0 g simulations. Several experiments in space show that mitogenic T cell activation is lost at 0 g. Immunocytochemistry indicates that such effect is associated with changes of the cytoskeleton. Biochemical studies suggest that the lack of expression of the interleukin-2 receptor is one of the major causes of the loss of activity. In fact, interleukin-2 is the third signal required for full activation. In order to deepen our investigations we are now working with the free-fall machine, FFM, invented by D. Mesland, and with the random positioning machine, RPM, or three-dimensional clinostat, developed by T. Hoson. The FFM produces periods of free-fall lasting approximately 800 ms followed by bounces of 15-30 g lasting 45-60 ms. The RPM eliminates the effect of gravity by rotating biological specimen randomly around two orthogonal axes. While the FFM failed to reproduce the results obtained with T lymphocytes in space, the data from the RPM are in good agreement with those in real microgravity. In fact, the inhibition of the mitotic index in the RPM is 89% compared to static controls. The RPM (as the FFM) can carry markedly larger specimen than the fast rotating clinostat and thus allows to conduct comprehensive studies to select suitable biological objects for further investigations in space.     

Concept of monitoring for thermostressed state and service life of aircraft gas turbine engine blades

A concept of monitoring for material properties with residual life estimation of rotor blades for gas turbine engines is proposed. The structure of on-board control and conditionmonitoring system based on the intelligent pyrometer module with the algorithm for calculating the residual life of turbine rotor blades is described.     

Identification Techniques for SARSAT Signals

A process for the identification of emergency locator transmitter (ELT) signals related to search and rescue satellite-aided tracking (SARSAT) is presented. The ELT identification process is particularly important in order to increase the probability of detection and eliminate sources of interference from the data set. A set of ELT signal parameters is introduced and methods for estimating these parameters are developed. A theoretical analysis and performance evaluation of these methods is provided.