LET variation measurements behind different absorber thicknesses on COSMOS-1129 satellite

LET variation with the absorber thickness was measured by plastic detectors exposed on COSMOS-1129 satellite.     

Intrinsic time scale for reconnection on the dayside magnetopause

Recently much attention has been focused on the transient behavior of the magnetopause in response to pressure pulses and southward fluctuations of the interplanetary magnetic field. We examine the motion of the magnetopause behind the foreshock and conclude that this motion is affected by foreshock pressure variations but not by fluctuations in the direction of the magnetic field. Neither magnetopause erosion nor flux transfer event occurrence is controlled by the foreshock. On the contrary, flux transfer events occur at times of steady IMF and thier quasi-periodic behavior is controlled by the magnetopause or the magnetosphere and is not driven by the external boundary conditions. Since flux transfer events are clearly due to reconnection, this observation implies that the IMF must be southward some time perhaps as long as 7 minutes before flux transfer begins.     

Imaging the solar corona in the EUV

The SOHO (SOlar and Heliospheric Observatory) satellite was launched on December 2nd 1995. After arriving at the Earth-Sun (L1) Lagrangian point on February 14th 1996, it began to continuously observe the Sun. As one of the instruments onboard SOHO, the EIT (Extreme ultraviolet Imaging Telescope) images the Sun's corona in 4 EUV wavelengths. The He II filter at 304 Å images the chromosphere and the base of the transition region at a temperature of 5 − 8 × 10⁴ K; the Fe IX–X filter at 171 Å images the corona at a temperature of 1.3 × 10⁶ K; the Fe XII filter at 195 Å images the quiet corona outside coronal holes at a temperature of 1.6 × 10⁶ K; and the Fe XV filter at 284 Å images active regions with a temperature of 2.0 × 10⁶ K. About 5000 images have been obtained up to the present. In this paper, we describe also some aspects of the telescope and the detector performance for application in the observations. Images and movies of all the wavelengths allow a look at different phenomena present in the Sun's corona, and in particular, magnetic field reconnection.     

Non-linear resonant excitation of whistler mode waves in the Earth's ionosphere

We examine the resonant non-linear interaction in the Earth's ionosphere of two powerful high frequency radio beams with frequencies f ₁ and f ₂ (both larger than the plasma frequency at F2_max) and wave numbers k ₁ and k ₂ such that a whistler mode wave can be excited with a frequency f ₃ = f ₁ — f ₂ and a wave number k ₃ = k ₁ – k ₂. The feasibility of an effective ground based installation, sited at low latitudes, is discussed and the field strength of the wave emerging from a 10 km wide ionospheric region illuminated by the beams is evaluated for a range of transmitted frequencies, beam orientations and plasma frequencies in the interaction region. It is suggested that the longitude dependence of the enhancement of VLF noise bands detected by the Ariel 3 satellite may be due to a non-linear interaction of this type between any two or more medium wavelength signals from areas where there is a high concentration of commercial broadcasting stations, such as the NE region of the U.S.A.     

Modified Generalized Sign Test Processor for 2-D Radar

The modified generalized sign test processor is a nonparametric, adaptive detector for 2-D search radars. The detector ranks a sample under test with its neighboring samples and integrates (on a pulse-to-pulse basis) the ranks with a two-pole filter. A target is declared when the integrated output exceeds two thresholds. The first threshold is fixed and yields a 10-6 probability of false alarm when the neighboring samples are independent and identically distributed. The second threshold is adaptive and maintains a low false-alarm rate when the integrated neighboring samples are correlated and when there are nonhomogeneities, such as extraneous targets, in the neighboring cells. Using Monte Carlo techniques, probability of false-alarm results, probability of detection curves, and angular accuracy curves have been generated for this detector. The detector was built and PPI photographs are used to indicate the detector's performance when the radar is operated over land clutter.     

The German space processing programme TEXUS with sounding rockets

This paper reports on the objectives of the German space processing programme with sounding rockets and the scientific results obtained thus far.     

An approach to forming the design performance of the attitude control system for small spacecraft

The elements for various types of attitude control systems used in a number of small spacecraft are considered. An approach for assessment of such system effectiveness based on design requirements for spacecraft purpose and restriction in accuracy, mass and energy is proposed.     

Fuzzy logic rule as a method for making a design decision in rocketry development

The paper provides a method for multi-criteria selection of the optimal structural layout option based on a fuzzy logic inference that allows for uncertainties in engineering and operates with heterogeneous information of the qualitative and quantitative nature for the systems being designed.     

Study of thin-walled parts shaping process based on flanging and embossing

This paper presents the results of analyzing the shaping of thin-walled conical parts with the uniform thickness along generatrix.