透博梅卡公司探索新的涡轴发动机

虽然透博梅卡公司现在每年销售发动机超过650台,但它们却认为已经到了研制替换轴功率为450～670千瓦级发动机的时候了.     

Ionization processes in the heliosphere — Rates and methods of their determination

The rates of the most important ionization processes acting in interplanetary space on interstellar H, He, C, O, Ne and Ar atoms are critically reviewed in the paper. Their long-term modulations in the period 1974 – 1994 are reexamined using updated information on relevant cross-sections as well as direct or indirect data on variations of the solar wind/solar EUV fluxes based on IMP 8 measurements and monitoring of the solar 10.7 cm radio emission. It is shown that solar cycle related variations are pronounced (factor of 3 between maximum and minimum) especially for species such as He, Ne, C for which photoionization is the dominant loss process. Species sensitive primarily to the charge-exchange (as H) show only moderate fluctuations 20% around average. It is also demonstrated that new techniques that make use of simultaneous observations of neutral He atoms on direct and indirect orbits, or simultaneous measurements of He⁺ and He⁺⁺ pickup ions and solar wind particles can be useful tools for narrowing the uncertainties of the He photoionization rate caused by insufficient knowledge of the solar EUV flux and its variations.     

THE WIDE-BAND PLASMA WAVE INVESTIGATION

As part of the Cluster Wave Experiment Consortium (WEC), the Wide-Band (WBD) Plasma Wave investigation is designed to provide high-resolution measurements of both electric and magnetic fields in selected frequency bands from 25 Hz to 577 kHz. Continuous waveforms are digitised and transmitted in either a 220 kbit s^-1 real-time mode or a 73 kbit s^-1 recorded mode. The real-time data are received directly by a NASA Deep-Space Network (DSN) receiving station, and the recorded data are stored in the spacecraft solid-state recorder for later playback. In both cases the waveforms are Fourier transformed on the ground to provide high-resolution frequency-time spectrograms. The WBD measurements complement those of the other WEC instruments and also provide a unique new capability for performing very-long-baseline interferometry (VLBI) measurements.     

Near Infrared Spectrometer for the Near Earth Asteroid Rendezvous Mission

The Near-Infrared Spectrometer (NIS) instrument on the Near-Earth Asteroid Rendezvous (NEAR) spacecraft is designed to map spectral properties of the mission target, the S-type asteroid 433 Eros, at near-infrared wavelengths diagnostic of the composition of minerals forming S asteroids. NIS is a grating spectrometer, in which light is directed by a dichroic beam-splitter onto a 32-element Ge detector (center wavelengths, 816–1486 nm) and a 32-element InGaAs detector (center wavelengths, 1371–2708 nm). Each detector reports a 32-channel spectrum at 12-bit quantization. The field-of-view is selectable using slits with dimensions calibrated at 0.37° × 0.76° (narrow slit) and 0.74° × 0.76° (wide slit). A shutter can be closed for dark current measurements. For the Ge detector, there is an option to command a 10x boost in gain. A scan mirror rotates the field-of-view over a 140° range, and a diffuse gold radiance calibration target is viewable at the sunward edge of the field of regard. Spectra are measured once per second, and up to 16 can be summed onboard. Hyperspectral image cubes are built up by a combination of down-track spacecraft motion and cross-track scanning of the mirror. Instrument software allows execution of data acquisition macros, which include selection of the slit width, number of spectra to sum, gain, mirror scanning, and an option to interleave dark spectra with the shutter closed among asteroid observations. The instrument was extensively characterized by on-ground calibration, and a comprehensive program of in-flight calibration was begun shortly after launch. NIS observations of Eros will largely be coordinated with multicolor imaging from the Multispectral Imager (MSI). NIS will begin observing Eros during approach to the asteroid, and the instrument will map Eros at successively higher spatial resolutions as NEAR's orbit around Eros is lowered incrementally to 25 km altitude. Ultimate products of the investigation will include composition maps of the entire illuminated surface of Eros at spatial resolutions as high as 300 m.     

Effects of polarization and resolution on SAR ATR

Lincoln Laboratory is investigating the detection and classification of stationary ground targets using high resolution, fully polarimetric, synthetic aperture radar (SAR) imagery. A study is summarized in which data collected by the Lincoln Laboratory 33 GHz SAR were used to perform a comprehensive comparison of automatic target recognition (ATR) performance for several polarization/resolution combinations. The Lincoln Laboratory baseline ATR algorithm suite was used, and was optimized for each polarization/resolution case. Both the HH polarization alone and the optimal combination of HH, HV, and VV were evaluated; the resolutions evaluated were 1 ft/spl times/1 ft and 1 m/spl times/1 m. The data set used for this study contained approximately 74 km/sup 2/ of clutter (56 km/sup 2/ of mixed clutter plus 18 km/sup 2/ of highly cultural clutter) and 136 tactical target images (divided equally between tanks and howitzers).     

Automated air defense system using knowledge-based system

The proposed KAAD (knowledge-based automated air defense) system demonstrates a man-machine environment for airspace defense systems. When the unknown aircraft is hostile, a threat rating and response methods are generated by the system. It serves as a double-check decision-making system for a war control center. In addition to this application, the KAAD system can also be a useful tool as a training program for the war controller. The capabilities of the system are limited due to the shortage of knowledge resources. It requires communications among war controllers and air fighter pilots to organize a practical knowledge base. It is shown that the KAAD system can be combined with an automated ATC (air traffic control) system to become a practical system for air defense applications     

Galileo Probe Nephelometer experiment

The objective of the Nephelometer Experient aboard the Probe of the Galileo mission is to explore the vertical structure and microphysical properties of the clouds and hazes in the atmosphere of Jupiter along the descent trajectory of the Probe (nominally from 0.1 to > 10 bars). The measurements, to be obtained at least every kilometer of the Probe descent, will provide the bases for inferences of mean particle sizes, particle number densities (and hence, opacities, mass densities, and columnar mass loading) and, for non-highly absorbing particles, for distinguishing between solid and liquid particles. These quantities, especially the location of the cloud bases, together with other quantities derived from this and other experiments aboard the Probe, will not only yield strong evidence for the composition of the particles, but, using thermochemical models, for species abundances as well. The measurements in the upper troposphere will provide ground truth data for correlation with remote sensing instruments aboard the Galileo Orbiter vehicle. The instrument is carefully designed and calibrated to measure the light scattering properties of the particulate clouds and hazes at scattering angles of 5.8°, 16°, 40°, 70°, and 178°. The measurement sensitivity and accuracy is such that useful estimates of mean particle radii in the range from about 0.2 to 20 can be inferred. The instrument will detect the presence of typical cloud particles with radii of about 1.0 , or larger, at concentrations of less than 1 cm³.Deceased.     

Energetic Particles Investigation (EPI)

The Energetic Particles Investigation (EPI) instrument operates during the pre-entry phase of the Galileo Probe. The major science objective is to study the energetic particle population in the innermost regions of the Jovian magnetosphere — within 4 radii of the cloud tops — and into the upper atmosphere. To achieve these objectives the EPI instrument will make omnidirectional measurements of four different particle species — electrons, protons, alpha-particles, and heavy ions (Z > 2). Intensity profiles with a spatial resolution of about 0.02 Jupiter radii will be recorded. Three different energy range channels are allocated to both electrons and protons to provide a rough estimate of the spectral index of the energy spectra. In addition to the omnidirectional measurements, sectored data will be obtained for certain energy range electrons, protons, and alpha-particles to determine directional anisotropies and particle pitch angle distributions. The detector assembly is a two-element telescope using totally depleted, circular silicon surfacebarrier detectors surrounded by a cylindrical tungsten shielding with a wall thickness of 4.86 g cm^-2. The telescope axis is oriented normal to the spherical surface of the Probe's rear heat shield which is needed for heat protection of the scientific payload during the Probe's entry into the Jovian atmosphere. The material thickness of the heat shield determines the lower energy threshold of the particle species investigated during the Probe's pre-entry phase. The EPI instrument is combined with the Lightning and Radio Emission Detector (LRD) such that the EPI sensor is connected to the LRD/EPI electronic box. In this way, both instruments together only have one interface of the Probe's power, command, and data unit.     

CFAR data fusion center with inhomogeneous receivers

Detection systems with distributed sensors and data fusion are increasingly used by surveillance systems. A system formed by N inhomogeneous constant false alarm rate (CFAR) detectors (cell-averaging (CA) and ordered statistic (OS) CFAR detectors) is studied. A recursive formulation of an algorithm that permits a fixed level of false alarms in the data fusion center is presented, to set the optimum individual threshold levels in the CFAR receivers and the optimum `K out of N' decision rule in order to maximize the total probability of detection. The algorithm also considers receivers of different quality or with different communication channel qualities connecting them with the fusion center. This procedure has been applied to several hypothetical networks with distributed CA-CFAR and OS-CFAR receivers and for Rayleigh targets and interference, and it was seen that in general the fusion decision OR rule is not always the best