Variations of the magnetosheath ion flux and geomagnetic activity

The magnetosheath plays a dominant role in the Sun–Earth connection because the magnetosheath field and plasma actually interact with the magnetosphere. The interactions change the magnetospheric magnetic field from its nominal value through a long chain of different processes. The change is usually described by geomagnetic indices and thus it can be expected that these indices would reflect changes in the magnetosheath. The present paper analyzes the relation between geomagnetic activity characterized by changes of the K_p, D_ST and AE indices and ion flux measured in the night-side magnetosheath. The results suggest a weak dependence of the D_ST index on the ion flux in the inner magnetosheath that is connected with a magnetopause displacement. On the other hand, fluctuations of the ion flux in the analyzed frequency range do not correlate with any of the indices.     

Improvement in the GERB short wave flux estimations over snow covered surfaces

Because space-borne radiometers do not measure the Earth’s outgoing fluxes directly, angular distribution models (ADMs) are required to relate actual radiance measurement to flux at given solar angle, satellite-viewing geometries, surface, and atmospheric conditions. The conversion of one footprint broad-band radiance into the corresponding flux requires therefore one to first characterize each footprint in terms of surface type and cloud cover properties to properly select the adequate ADM.

A snow (and sea-ice) retrieval technique based on spectral measurements from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board Meteosat 8 is presented. It has been developed to improve the scene identification and thus the ADM selection in the near-real time processing of the Geostationary Earth Radiation Budget (GERB) data at the Royal Meteorological Institute of Belgium. The improvement in the GERB short wave flux estimations over snow covered scene types resulting from angular conversion using dedicated snow ADMs (e.g., empirical snow ADMs and/or pre-computed theoretical snow ADM) instead of empirical snow-free ADMs is discussed.     

New line profiles of Li–H2 for brown dwarfs

In order to calculate the opacity of a gas it is necessary to consider how its constituent atoms are perturbed by the surrounding medium. This is required both in order to calculate the equation of state, and in order to determine the profiles of the spectrum lines. In this work we report new theoretical Li line profiles perturbed by H₂ and their dependence with temperature.     

Modeling the protection system components of the space stationelectric power system

To facilitate protection system studies on the space station electric power system, there is a need to develop a model that can accurately and conveniently simulate both the power system and the protection system. Models for two major protective devices, the remote bus isolator and the remote power controller, are described. These models have been installed in a power system model resembling one channel of the space station power system. The usefulness of these models in protection system studies Is demonstrated     

Thermodynamic cycles for spacecraft power plants

A problem of applying closed multiloop thermodynamic cycles with mixing of dissimilar working gases in spacecraft power plants has been considered. The advantage of these cycles that is due to reduction of a heat quantity being rejected into space has been shown for ecologically clean generation of electric energy in prolonged space flights.     

Adaptive Trackers Based on Continuous Learning Theory

The theory of ?continuous learning? is applied here to the design of nonlinear sampled-data trackers. This theory provides a continuous-motion approximation of the discrete or sampled motion of the actual tracker. The theory prodicts the transient-response performance of the tracker as well as the mean-square errors caused by noise and statistical fluctuations in the signal. Numerical examples of first-order and second-order trackers designed by this technique are presented. These examples illustrate the adaptive behavior predicted by the technique. In one of these examples the trade-off between transient-response performance and the suppression of noise-induced tracking errors is demonstrated.     

Explicit solutions for some simple decentralized detection problems

A decentralized detection problem is considered in which a number of identical sensors transmit a finite-valued function of their observations to a fusion center which makes a final decision on one of M alternative hypotheses. The authors consider the case in which the number of sensors is large, and they derive (asymptotically) optimal rules for determining the messages of the sensors when the observations are generated from a simple and symmetrical set of discrete distributions. They also consider the tradeoff between the number of sensors and the communication rate of each sensor when there is a constraint on the total communication rate from the sensors to the fusion center. The results suggest that it is preferable to have several independent sensors transmitting low-rate (coarse) information instead of a few sensors transmitting high-rate (very detailed) information. They also suggest that an M-ary hypothesis testing problem can be viewed as a collection of M(M-1)/2 binary hypothesis testing problems. From this point of view the most useful messages (decision rules) are those that provide information to the fusion center that is relevant to the largest possible numbers of these binary hypothesis testing problems     

Validation and comparison of coordinated turn aircraft maneuvermodels

A major challenge posed by aircraft tracking problems is the nondeterministic nature of an aircraft flight, due to the difficulty of predicting the pilot's actions. Accurate aircraft maneuver models are however highly desirable, particularly in air defense applications, to achieve accurate tracking and prediction. Through analysis of actual fighter aircraft trajectories and comparison with the Singer maneuver model, particularly in terms of prediction performance, coordinated turn (CT) aircraft maneuver models are presented, compared, and validated. A more general CT model is shown to better model actual trajectories than the classical CT model used in the literature     

A Problem of choosing an optimal number of information unmanned aerial vehicles

Using formalism of the queueing theory, we propose two-objective models for optimizing the number of unmanned aerial vehicles (UAV) designed for remote monitoring (reconnaissance) of certain regions. A model that takes into account the UAV failure in performing a flight mission is considered. The numerical method and examples of solving problems stated are presented.