Solar UV irradiance variation during cycles 22 and 23

The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) aboard the Upper Atmosphere Research Satellite (UARS) has been measuring solar UV irradiances since October 1991, a period which includes the decline of solar cycle 22 followed by the rise of cycle 23. Daily solar measurements include scans over the wavelength range 115–410 nm at 1.1 nm resolution. As expected, the measured time series of UV irradiances exhibit strong periodicities in solar cycle and solar rotation. For all wavelengths, the UV irradiance time series are similar to that of the Mg II core-to-wing ratio. During solar cycle 22, the irradiance of the strong Ly- line varied by more than a factor of two. The peak-to-peak irradiance variation declined with increasing wavelength, reaching 10% just below the Al edge at 208 nm. Between the Al edge and 250 nm the variation was 6–7%. Above 250 nm, the variation declines further until none is observed above 290 nm. Preliminary results for the first portion of cycle 23 indicate that the far UV below the Al edge is rising at about the same rate as the Mg II index while the irradiances in the Ly- emission line and for wavelengths longer than the Al edge are rising more slowly — even after accounting for the lower level of activity of cycle 23.     

On electromagnetic phenomena in Mercury’s magnetosphere

Mercury has a small but intriguing magnetosphere. In this brief review, we discuss some similarities and differences between Mercury’s and Earth’s magnetospheres. In particular, we discuss how electric and magnetic field measurements can be used as a diagnostic tool to improve our understanding of the dynamics of Mercury’s magnetosphere. These points are of interest to the upcoming ESA-JAXA BepiColombo mission to Mercury.     

Design and characteristics of a multiband communication satelliteantenna system

Feasibility studies on a multiband communication satellite antenna system and the key technologies involved in devising this system are described. The proposed multiband communication satellite utilizes four frequency bands: Ka (30/20 GHz), Ku (14/12 GHz), C (6/4 GHz), and S (2.6/2.5 GHz). It has six beam configurations, three multibeam and three shaped-beam. The following key technologies are presented: (1) a low-loss frequency selective subreflector (FSR) for compact feeds, (2) a low-loss and broadband frequency selective surface (FSS), and (3) a highly accurate and reliable mesh reflector     

The Generation of Correlated Weibull Clutter for Signal Detection Problems

A method is discussed for generating Weibull vectors with a desired correlation matrix and specified parameters. Such vectors may represent samples of a correlated clutter signal. The presented method makes use of a suitable nonlinear transformation of random Gaussian vectors with correlated components. Computational aspects of the method are also discussed.     

High-Speed Homopolar Inductor Alternators of Minimum Leakage Reactance

The leakage reactance of the machine is expressed as an equation involving slot leakage, end-connection leakage, differential leakage, stator-halves leakage, and tooth-top leakage reactance. This leakage reactance equation, or objective function, is then minimized under suitable constraints. Geometric programming is used to carry through the optimization procedure. A computer program is developed and applied to find the optimum leakage reactance for a 95 kVA, 208 V, wye-connected, 40 800 r/min aerospace alternator, using 8-, 10-, and 12-pole machines.     

Attitude Determination Via Nonlinear Filtering

The theory of nonlinear filtering has been applied to the problem of the attitude determination of a satellite. Two approximation methods have been studied with a view to practical implementation. Computer simulation results are included.     

Aerodynamic Design Method of Integrated Aircraft with Submerged Intake Devices and Power Plant Included into Airframe Carrying System

This paper presents a theoretically and practically grounded architecture of design methods combination. A possibility and completeness of developing integral design solutions and intensifying the design process are provided by redistribution of emphases of numerical and natural experiments.     

The Electric Antennas for the STEREO/WAVES Experiment

The STEREO/WAVES experiment is designed to measure the electric component of radio emission from interplanetary radio bursts and in situ plasma waves and fluctuations in the solar wind. Interplanetary radio bursts are generated from electron beams at interplanetary shocks and solar flares and are observed from near the Sun to 1 AU, corresponding to frequencies of approximately 16 MHz to 10 kHz. In situ plasma waves occur in a range of wavelengths larger than the Debye length in the solar wind plasma λ _D ≈10 m and appear Doppler-shifted into the frequency regime down to a fraction of a Hertz. These phenomena are measured by STEREO/WAVES with a set of three orthogonal electric monopole antennas. This paper describes the electrical and mechanical design of the antenna system and discusses efforts to model the antenna pattern and response and methods for in-flight calibration.     

Notes on SCPC-FM System Design and Performance

In many domestic satellite communication systems single-channel per-carrier FM (SCPC-FM) has become the accepted transmission method for thin route communication. The SCPC-FM modem operates over a wide range of carrier frequencies and is designed to use satellite power and bandwidth efficiently. It incorporates elements which make the signal transfer complex, so the system behavior is not immediately obvious. This article investigates the signal processes and analyzes the performance of a companded and preemphasized SCPC-FM system and it furnishes insight into the choice of crucial system parameters.