Book reviews

Space Science Reviews -     

The Radio Frequency Subsystem and Radio Science on the MESSENGER Mission

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Radio Frequency (RF) Telecommunications Subsystem is used to send commands to the spacecraft, transmit information on the state of the spacecraft and science-related observations, and assist in navigating the spacecraft to and in orbit about Mercury by providing precise observations of the spacecraft’s Doppler velocity and range in the line of sight to Earth. The RF signal is transmitted and received at X-band frequencies (7.2 GHz uplink, 8.4 GHz downlink) by the NASA Deep Space Network. The tracking data from MESSENGER will contribute significantly to achieving the mission’s geophysics objectives. The RF subsystem, as the radio science instrument, will help determine Mercury’s gravitational field and, in conjunction with the Mercury Laser Altimeter instrument, help determine the topography of the planet. Further analysis of the data will improve the knowledge of the planet’s orbital ephemeris and rotation state. The rotational state determination includes refined measurements of the obliquity and forced physical libration, which are necessary to characterize Mercury’s core state.     

在服役中航空涡轮发动机的状态监控

本文是介绍涡轮发动机使用状态监控方面的一个新的综述.状态监控过程是使用各种不同的原理去跟踪发动机性能并找出机械故障模式的方法.本文也提出将监控资料转化为供航空公司使用的精确的维护建议需要的经验样本.     

Tether applications: Note on an article by J. A. Carroll

Reference is given to two early publications of the author about tether applications for scientific purposes.     

TeV gamma-rays from proton blazars

Proton acceleration in nearby blazars can be diagnosed measuring their intense TeV -ray emission. Flux predictions for 1101+384 (Mrk421) and 1219+285 (ON231), both strong EGRET sources (0.1 – 10 GeV), are obtained from model spectra of unsaturated synchrotron pair cascades fitted to publicly available multifrequency data. An experimen tal effort to confirm the predicted emission in the range 1–10 TeV would be of great importance for the problems of the origin of cosmic rays, the era of galaxy formation and the cosmological distance scale.     

ESA''s new intellectual property policy

This paper outlines the new intellectual property policy for ESA research and development contracts and how the new general contract provisions achieve a balance between the interests of the individual contractor, the member states and ESA's need to improve the competitive position of European industry as a whole.     

Energy sources for the ionosphere—a survey

An outline is given of early aeronomical ideas about the formation of the ionosphere by solar wave radiation, and its development under the impetus of increasing basic knowledge. In particular, the development concerning solar radiation in the far ultraviolet and X-ray ranges is discussed (Sect. 1). General considerations on the relation with observable ionospheric parameters are given in Sect. 2 while the individual layers are discussed in Sect. 3. It is found that elder investigations, with wrong assumptions came to the right densities while their estimates of production rates were far too low. Since two years only satellite and laboratory data allow satisfying estimates.     

New description of the electron density profile

Methods are described by which the desired analytical representation of the whole profile might be reached while enforcing the most important observed physical features. An outline of future work in this connection is given.     

Feature enhancement and ATR performance using nonquadratic optimization-based SAR imaging

We present an evaluation of the impact of a recently proposed synthetic aperture radar (SAR) imaging technique on feature enhancement and automatic target recognition (ATR) performance. This image formation technique is based on nonquadratic optimization, and the images it produces appear to exhibit enhanced features. We quantify such feature enhancement through a number of criteria. The findings of our analysis indicate that the new feature-enhanced SAR image formation method provides images with higher resolution of scatterers, and better separability of different regions as compared with conventional SAR images. We also provide an ATR-based evaluation. We run recognition experiments using conventional and feature-enhanced SAR images of military targets, with three different classifiers. The first classifier is template based. The second classifier makes a decision through a likelihood test, based on Gaussian models for reflectivities. The third classifier is based on extracted locations of the dominant target scatterers. The experimental results demonstrate that the new feature-enhanced SAR imaging method can improve the recognition performance, especially in scenarios involving reduced data quality or quantity.     

Aerodynamic scaling to free flight conditions: Past and present

This report summarizes some of the problems when wind tunnel data should be scaled to free flight conditions. The main challenges in performing this extrapolation is how model support, wall interference, aeroelastic effects and a potentially lower Reynolds number in the wind tunnel should be corrected. A historical review of scale effects is presented showing wind tunnel to flight discrepancies of different types of aircraft configurations. An overview of scaling methodologies and Reynolds number effects are presented and discussed. Some modern approaches where computational fluid dynamics (CFD) are used, together with wind tunnel testing, in order to identify scaling phenomena are presented as well.