Gamma-telescope with very high angular and spectral resolution

New type of gamma-telescope with angular resolution about several seconds of arc and spectral resolution ΔE/E <0.1% is proposed. In this instrument a position sensitive detector is used together with random mask, crystal diffractor and stellar sensor. The scientific objectives and the possible ways to carry out the first experiment with this telescope are discussed.     

Simulation experiments of the cosmic ray isotope telescope on ETS VI

A computer simulation was carried out to evaluate the basic characteristics of a Δ E×E cosmic ray telescope consisting of 23 solid state detectors including 3 position sensitive detectors with large effective area. Based on the simulation, the geometric factor of the telescope is deduced to be as large as 22.5 cm²sr, almost independent of charge and energy concerned. The energy ranges to be covered by the telescope are, for example, 18–98 MeV/n for Li and 56–339 MeV/n for Fe. By analyzing simulated data, the mass resolution for iron in the overall energy range covered by the telescope is estimated as about 0.22 amu in standard deviation. The expected counting rates and mass-histograms are simulated for Galactic cosmic rays and solar energetic particles.     

An imaging telescope for soft gamma ray astronomy

A telescope capable of producing images of the gamma ray sky in the energy range 0.2–20 MeV with an angular resolution of a few tenths of a degree is presented. This capability is achieved by means of a large array of Sodium Iodide position sensitive elements together with a coded imaging mask. The expected performance, derived from calculations and preliminary laboratory tests, is described.     

Hadamard X-ray Spectro-telescope

The Hadamard X-ray Spectro-telescope consists of a flat Bragg crystal, an Hadamard mask and an imaging proportional counter. We have achieved α??α≈50, which is limited by the position resolution of the detector. This telescope is useful to observe the spectral structure of extended X-ray sources. We introduce a new type of read out method (Grouped Wire Method) for the position sensitive proportional counter in order to get high energy and position resolutions for the Hadamard Spectro-telescope. In principle, this method is capable of obtaining the desired linearity over the whole area of the detector.     

The position sensitive low energy detector on board the ZEBRA telescope

In order to improve the low energy capability (15 ÷ 150 KeV) of the balloon borne “ZEBRA” low energy gamma imaging telescope (150 KeV-20 MeV), a large area, high spectral resolution (5% at 60 KeV), low background detector has been designed and is now under development.It consists of two MultiWire Spectroscopic Proportional Counter (SPC), escape gated, that have a sensitive area of 6000 cm², and are placed above the large area array of sodiumiodide position sensitive elements.     

RadioAstron orbit determination and evaluation of its results using correlation of space-VLBI observations

A crucial part of a space mission for very-long baseline interferometery (VLBI), which is the technique capable of providing the highest resolution images in astronomy, is orbit determination of the mission’s space radio telescope(s). In order to successfully detect interference fringes that result from correlation of the signals recorded by a ground-based and a space-borne radio telescope, the propagation delays experienced in the near-Earth space by radio waves emitted by the source and the relativity effects on each telescope’s clock need to be evaluated, which requires accurate knowledge of position and velocity of the space radio telescope. In this paper we describe our approach to orbit determination (OD) of the RadioAstron spacecraft of the RadioAstron space-VLBI mission. Determining RadioAstron’s orbit is complicated due to several factors: strong solar radiation pressure, a highly eccentric orbit, and frequent orbit perturbations caused by the attitude control system. We show that in order to maintain the OD accuracy required for processing space-VLBI observations at cm-wavelengths it is required to take into account the additional data on thruster firings, reaction wheel rotation rates, and attitude of the spacecraft. We also investigate into using the unique orbit data available only for a space-VLBI spacecraft, i.e. the residual delays and delay rates that result from VLBI data processing, as a means to evaluate the achieved OD accuracy. We present the results of the first experience of OD accuracy evaluation of this kind, using more than 5000 residual values obtained as a result of space-VLBI observations performed over 7 years of the RadioAstron mission operations.     

Multiple Coulomb scattering method to reconstruct low-energy gamma–ray direction in the GAMMA-400 space-based gamma–ray telescope

The GAMMA-400 currently developing space-based gamma-ray telescope is designed to measure the gamma-ray fluxes in the energy range from ～20?MeV to several TeV in the highly elliptic orbit (without shadowing the telescope by the Earth) continuously for a long time. The physical characteristics of the GAMMA-400 gamma-ray telescope, especially the angular and energy resolutions (at 100-GeV gamma rays they are ～0.01° and ～1%, respectively), allow us to consider this space-based experiment as the next step in the development of extraterrestrial high-energy gamma-ray astronomy. In this paper, a method to improve the reconstruction accuracy of incident angle for low-energy gamma rays in the GAMMA-400 space-based gamma-ray telescope is presented. The special analysis of topology of pair-conversion events in thin layers of converter was performed. Applying the energy dependence of multiple Coulomb scattering for pair components, it is possible to estimate the energies for each particle, and to use these energies as weight in the angle reconstruction procedure. To identify the unique track in each projection the imaginary curvature method is applied. It allows us to obtain significantly better angular resolution in comparison with other methods applied in current space-based experiments. When using this method for 50-MeV gamma rays the GAMMA-400 gamma-ray telescope angular resolution is about 4°.     

Vega project — Three channel spectrophotometer for the Halley''s comet investigation

A spectrometer for the Halley's Comet Investigation after the VEGA Project is described in the present work. It consists of a telescope and three spectral channels: UV (120 – 290 nm), resolution Δ λ / λ = 170; VIS (280 – 710 nm), resolution Δ λ / λ = 170; IR (950 – 1900 nm), resolution Δ λ / λ = 70.

With the help of two-coordinate scanner, the secondary mirror of the telescope allows spatial scanning of the Comet with a frame 2°×1,5° with 105 different pixels.     

轻型空间相机桁架结构设计与模态分析

为设计适合轻型高分辨空间相机的桁架结构,研究了模态分析的方法和桁架设计中需要考虑的问题.通过对不同的次镜支撑结构进行模态分析和对比,提出了适用于轻型相机的三翼中心三角次镜支撑结构,并完成了整体桁架结构的设计.有限元分析结果表明,所设计的桁架结构具有固有频率高、质量轻等优点,能够满足轻型空间相机的要求,并可以作为其他大口径空间相机桁架结构的设计参考.      

A directional gamma-ray telescope using coded aperture techniques

A directional detector for γ-ray astronomy has been developed to image sources in the energy range 0.1 to 5 MeV. An array of 35 gain stabilized bismuth germanate detectors, together with a coded aperture mask based on a Uniformly Redundant Array (URA), allows imaging in 4° square sky bins over a 16° X 24° field-of-view. The position of a strong point source, such as the Crab Nebula, can be determined to within ?1°. A complementary “anti-mask” greatly reduces systematic effects arising from non-uniform background rates amongst the detectors. The telescope has an effective area of 190 cm² and an energy resolution of 19.5% FWHM at 662 keV. Results of laboratory tests of the imaging system, including the ability to image multiple sources, uniformity of response over the field-of-view, and the effect of the “anti-mask”, are in good agreement with computer simulations. Features of the flight detector system are described and results of laboratory tests and computer simulations are reviewed. A balloon flight of the telescope is planned for the fall of 1982.     

The ROSAT mission

A primary scientific objective of the ROSAT mission is to perform the first all-sky survey with an imaging X-ray telescope leading to an improvement in sensitivity by several orders of magnitude compared with previous surveys. A large number of new sources (? 10⁵) will be discovered and located with an accuracy of 1 arcmin or better. These will comprise almost all astronomical objects from nearby normal stars to distant quasistellar objects. After completion of the survey which will take half a year the instrument will be used for detailed observations of selected sources with respect to spatial structure, spectra and time variability. In this mode which will be open for guest observers ROSAT will provide substantial improvement over the imaging instruments of the Einstein observatory.The main ROSAT telescope consists of a fourfold nested mirror system with 83 cm aperture having three focal plane instruments. Two of them will be imaging proportional counters (0.1 – 2 keV) providing a field of view of 2°, an angular resolution of ≈ 30″ in the pointing mode and a spectral resolution ^ΔE/E ≈ 45% FWHM at 1 keV. The third focal instrument will be a high resolution imager (≈ 3″). The main ROSAT telescope will be complemented by a parallel looking Wide Field camera which extend the spectral coverage into the XUV band.     

天基通信与太空射电望远镜功能一体系统

摘要： 针对现有地基深空通信系统存在深空通信距离不够远、数传速率不够高等缺点,提出一种基于分布式协同控制的天基主动深空通信与太空射电望远镜功能一体系统.该系统部署在地球静止轨道上,由1颗馈源星、1颗中心星和4294颗小卫星（单元星）通过精密编队和在轨自主组装的方式构成,一体化集成天基主动深空通信功能和射电天文望远镜功能.该系统可以为深空探测器提供一个星地高速中转站,由于其部署在地球静止轨道,几乎不受大气云层影响,可以大幅度提升深空探测通信支持距离和数传速率,且能使射电天文望远镜的分辨率和灵敏度提升1~2个数量级.     

An imaging telescope for soft gamma-ray astronomy: The preliminary in-flight tests

A large area (6000 cm²) actively shielded low energy gamma-ray telescope is going to be built by an Anglo-Italian collaboration. The telescope, named ZEBRA, will be capable of producing images of the X and gamma ray sky in the energy range 0.015–20 MeV with an intrinsic angular resolution of a few tenths of a degree. A prototype detector has been built in order to experimentally study the main characteristics of the detection plane. The preliminary results obtained during a balloon flight from Trapani, Sicily in July 1981 are presented.     

Balloon-borne far-infrared spectrophotometry of the galactic center region

Far-infrared observations of the Galactic Center have been carried through with the MPE Im balloon-borne telescope “Golden Dragon”. The measurements are composed of photometric scanning (33–95 μm) of the inner 4′×4′ and low resolution spectroscopy (δ^ν = 10 cm^?1) of the center and of a position approximately 1.5′ to the north. A Mars spectrum has been obtained for calibration. The spatial resolution of the photometry map is increased using the Maximum Entropy Method and the resulting map is compared to other observations in the same and other spectral regions. A clear asymmetry in the ring-like structure around the center indicates the presence of noncircular motions. The shape of the spectra is fairly smooth with at least no prominent dust features. A simple modelling shows a drastic increase of column density within 2 pc from the center and a modest drop over the next 3 pc to the north.     

Simulated high resolution observation by the sigma telescope of the low energy gamma-ray emission from the galactic center region based on recent observational results

Simulated high resolution images of the galactic center region have been obtained for the SIGMA telescope, using recent observational data. It is shown that the next generation of gamma-ray imaging telescopes will be able to resolve this complex region of the sky.     

综合孔径射电望远镜冗余基线可见度噪声相关性对灵敏度的影响

综合孔径射电望远镜可见度噪声之间的相关性不但影响灵敏度的大小，而且影响阵列冗余对灵敏度的优化作用.本文研究对可见度噪声相关性起决定性作用的两个主要因素:目标场景亮温分布和接收机等效噪声温度，并利用仿真方法进行验证.通过灵敏度仿真实验，证明经过阵列冗余优化可以实现对灵敏度的优化，并且优化程度受到冗余基线可见度噪声之间相关性的影响.      

High spectral resolution line profiles and images of comet Halley

High-spectral-resolution line profiles and images of comet Halley were obtained in 1986 at the National Solar Observatory McMath telescope, using a dual-etalon Fabry-Perot spectrometer. The spectrometer was designed to obtain data in four distinct modes: (1) high-resolution (R = 200,000) scanning, (2) high-resolution imaging, (3) moderate resolution (R = 30,000) scanning, and (4) moderate resolution imaging. This paper describes the instrument and some examples of data obtained in the high-resolution scanning mode.     

The Frequency Agile Solar Radiotelescope

The Frequency Agile Solar Radiotelescope (FASR), a telescope concept currently under study, will be a ground based solar-dedicated radio telescope designed and optimized to produce high resolution, high-fidelity, and high-dynamic-range images over a broad frequency range (0.1–24 GHz). As such, FASR will address an extremely broad science program, including the nature and evolution of coronal magnetic fields, the physics of flares, drivers of space weather, and the quiet Sun. An important goal is to mainstream solar radio observations by providing a number of standard data products for use by the wider solar physics community. The instrument specifications and the key science elements that FASR will address are briefly discussed, as well as several operational issues.     

Orbiting VLBI

The technique of Michelson interferometry using synchronized radio telescope systems at great separations is known as Very-Long-Baseline Interferometry (VLBI). The method can be extended to give micro-arc-second angular resolution by using radio telescopes in space. There are no technical barriers, and several classes of conceptual systems can be specified.     

A new window on the cosmos: The Stratospheric Observatory for Infrared Astronomy (SOFIA)

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a joint US/German Project to develop and operate a gyrostabilized 2.5-m telescope in a Boeing 747-SP. This observatory will allow astronomical observations from 0.3 μm to sub-millimeter wavelengths at stratospheric altitudes as high as 45,000 ft where the atmosphere is not only cloud-free, but largely transparent at infrared wavelengths. The dynamics and chemistry of interstellar matter, and the details of embedded star formation will be key science goals. In addition, SOFIA’s unique portability will enable large-telescope observations at sites required to observe transient phenomena and location specific events. SOFIA will offer the convenient accessibility of a ground-based telescope for servicing, maintenance, and regular technology upgrades, yet will also have many of the performance advantages of a space-based telescope. Initially, SOFIA will fly with nine first-generation focal plane instruments that include broad-band imagers, moderate resolution spectrographs that will resolve broad features from dust and large molecules, and high resolution spectrometers capable of studying the chemistry and detailed kinematics of molecular and atomic gas. First science flights will begin in 2010, leading to a full operations schedule of about 120 8–10 h flights per year by 2014. The next call for instrument development that can respond to scientifically exciting new technologies will be issued in 2010. We describe the SOFIA facility and outline the opportunities for observations by the general scientific community with cutting edge focal plane technology. We summarize the operational characteristics of the first-generation instruments and give specific examples of the types of fundamental scientific studies these instruments are expected to make.