The use of diamond turned & replicated wolter 1 telescopes for high sensitivity X-ray astronomy

Following the success of Einstein, it is clear that telescopes of very large area (10 cm) with angular resolution (20) are needed for deep X-ray surveys and other observations. After a discussion of these objectives, which form the basis of the NASA LAMAR mission, the design & performance of a five mirror telescope is described. The system was studied for possible flight on Spacelab to undertake observations & to act as a prototype module for LAMAR. Both diamond turning & replication methods of mirror production are discussed. The performance of a single Wolter I telescope with diamond turned mirrors will be described.     

某涡喷发动机中介机匣振动模态分析

用多点激振单点拾振的脉冲激励试验模态测试方法，对某涡喷发动机中介机匣的振动特性进行了模态分析，对比了模型机中介机匣与改型机中介机匣的振动模态，试验结果表明模型机中介机匣在结构设计方面存在薄弱环节，其结果为某涡喷发动机结构设计、振动故障分析提供了依据。     

The X-ray imaging telescopes on Exosat

The instrument configuration and performance characteristics of the X-ray imaging telescopes on EXOSAT are described. The instrument comprises two fully independent Wolter I imaging telescopes. Each telescope can be used in either of two principal modes: (i) an imaging mode with either a position sensitive proportional counter or a channel multiplier array plate in the focal plane, (ii) a spectrometer mode which features a 500 lines/mm and/or a 1000 lines/mm transmission grating as dispersive element.Preliminary results from the calibration of the fully integrated experiment indicate an ultimate angular resolution of 8.5 arc sec full width at half maximum or 17.5 arc sec half-power beam width. The ultimate wavelength resolution in the spectrometer mode ranges from 1Å for wavelengths below 50Å, to 5Å at wavelengths near 300Å.A method for estimating the telescope performance is given which reasonably accounts for the influence of the X-ray source spectrum and the degree of interstellar absorption on the counting statistics.A comparison between EXOSAT and the EINSTEIN telescope in terms of band width/resolution and minimum source detectability shows an enhanced potential for EXOSAT relative to EINSTEIN for sources with T 10⁷K and low column densities (< 4 × 10²⁰cm^–2) and a reduced potential for sources with hard, or heavily cut-off, spectra.     

Book reviews

Space Science Reviews -     

Long duration hard X-ray transatlantic payload

This note describes the HXR80M large area hard X-Ray Astronomy experiment. The payload is scheduled for a flight on board of a transatlantic balloon to be launched the next July from the Milo Base (Sicily), in the framework of the CNR experimental transatlantic campaign.The detectors are two Multiwire Spectroscopic Proportional Chambers (MWSPC) having 2,700 cm² sensitive area each.The two detectors are filled with an extremely pure Xenon-Isobutane mixture (impurity less than 1ppm) at high pressure (3–6 Atm) in order to obtain good spectral resolution and high efficiency. The field of view of the MWSPC's is limited by an array of three collimators each, having respectively 8°×8° and 5°×5° FWHM.The on board data handling is performed by microprocessor controlled electronics. In particular a micro Multichannel Analyzer (μMCA) is employed to obtain the spectrum of the detected photons. The scientific and housekeeping data are send to ground through a 1.2 Kbit PCM HF Telemetry link.The scientific aim of the experiment is the survey of the sky belt around the 38th parallel and in particular the observation of faint galactic objects and galactic binary systems in the range 15–200 keV.     

The role of the united nations in promoting international cooperation in peaceful uses of outer space

The Committee on the Peaceful Uses of Outer Space (COPUOS) was established in 1959 by the United Nations General Assembly in order to review and foster international cooperation in the peaceful uses of outer space and to consider legal issues arising from the exploration of outer space. Since its establishment, the Committee has addressed such issues as benefits from space activities, the definition and delimitation of outer space and the use of the geostationary orbit, implications of remote sensing, space sciences, space-based communications, navigation and meteorological systems, as well as use of nuclear power sources in outer space, space debris and spin-off benefits of space technology. At its session in 1996, a symposium on the ‘Utilization of micro- and small satellites for the expansion of low-cost space activities, taking into particular account the needs of developing countries’ was organized by COSPAR and IAF to complement discussions on this theme. It was noted at the symposium that the increasing number of small satellites, in particular the proposed introduction of multi-satellite ‘constellations’ at low orbits, would result in concentrations of satellite mass at certain regions of space around the Earth. Special provisions would be needed to minimize the probability of satellite breakups and collisions which might create more space debris and compromise the future of spaceflight.     

切割法测取螺旋弹簧的残余应力

通常用实验方法测定园柱螺旋弹簧残余应力。本文提出了切割法对比测试技术，为确定高应力、高疲劳强度的弹簧制造工艺提供了依据。     

增压连续式跨声速风洞防喘振措施——旁路调节的研究

压缩机的设计与制造性能尚不能充分适应风洞的运行范围 ,安全、可靠的防喘振措施是保证风洞安全运行的重要条件之一。作者讨论了旁路调节作为风洞中防喘振措施的可行性。在考虑跨声速风洞中气体压缩性的基础上 ,给出了风洞中旁路调节的估算方法 ,分析和讨论了旁路对风洞性能的影响。结果表明 :旁路的增加 ,使风洞工作点向大流量、低压缩比方向移动 ,达到有效、可靠防喘振的目的     

Bacterial cellulose may provide the microbial-life biosignature in the rock records

Bacterial cellulose (BC) is a matrix for a biofilm formation, which is critical for survival and persistence of microbes in harsh environments. BC could play a significant role in the formation of microbial mats in pristine ecosystems on Earth. The prime objective of this study was to measure to what extent spectral and other characteristics of BC were changed under the performance of BC interaction with the earthly rock – anorthosite – via microorganisms. The spectral analyses (Fourier Transform Infrared FT-IR, spectroscopy, and atomic absorption spectroscopy) showed unprecedented accumulation of chemical elements in the BC-based biofilm. The absorption capacity of IR by BC was shielded a little by mineral crust formed by microorganisms on the BC-based biofilm surface, especially clearly seen in the range of 1200–900 cm⁻¹ in FT-IR spectra. Confocal scanning laser microscopy analysis revealed that elements bioleached from anorthosite created surface coats on the BC nanofibril web. At the same time, the vibrational spectra bands showed the presence of the characteristic region of anomeric carbons (960–730 cm⁻¹), wherein a band at 897 cm⁻¹ confirmed the presence of β-1, 4-linkages, which may serve as the cellulose fingerprint region. Results show that BC may be a biosignature for search signs of living organisms in rock records.