星载望远镜消光材料积分散射特性测试研究(英文)

在散射理论的基础上,介绍了一种星载望远镜消光材料积分散射特性测试装置,实现对星载望远镜消光材料散射特性更为全面的测量。对积分散射理论、系统构造、系统性能进行了阐述。对系统进行建模仿真分析,得到结论：消光材料的散射特性在不同点位和入射角下存在明显差异,系统能够测量多种条件下消光材料的散射特性,并得到消光材料全面的散射特性分布。研究结果为根据消光材料特性进行针对性设计提供了更全面、更准确的散射特性分布,为杂散光的测量与抑制、高性能光学仪器的研制与装调以及计算光学等领域的研究提供了参考。为空间引力波探测星载望远镜系统的材料选型、特性研究、杂散光分析与抑制提供了基础。     

空间引力波星载望远镜测试与评估技术研究进展

在空间引力波探测任务中,星载望远镜承担太空超长干涉光路双向光束准直的重要作用。空间引力波探测对星载望远镜提出了pm级光程稳定性和低于10⁻¹⁰级后向杂散光水平的极高要求。超高水平指标要求超过了当前测试技术的精度极限,因此,针对星载望远镜发展测试与评估技术并开展系统超高精度测试是空间引力波探测计划成功的重要前提。本文在概述国内外在研的空间引力波探测星载望远镜研制情况的基础上,重点围绕星载望远镜的核心技术指标——光程稳定性和后向杂散光,介绍了在研望远镜的测试技术发展现状和已经取得的部分测试成果,以及各研究单位进一步的测试计划,为我国的空间引力波探测的星载望远镜测试与评估技术发展提供参考。

     

Cooled infrared filters and dichroics for the James Webb Space Telescope Mid-Infrared Instrument

The cooled infrared filters and dichroic beam splitters manufactured for the Mid-Infrared Instrument are key optical components for the selection and isolation of wavelengths in the study of astrophysical properties of stars, galaxies, and other planetary objects. We describe the spectral design and manufacture of the precision cooled filter coatings for the spectrometer (7 K) and imager (9 K). Details of the design methods used to achieve the spectral requirements, selection of thin film materials, deposition technique, and testing are presented together with the optical layout of the instrument.     

Blackbody calibration sources of high accuracy for a spaceborne infrared instrument: the Along Track Scanning Radiometer

We describe the two 140-mm-aperture simulated blackbody sources used for the on-board calibration of the Along Track Scanning Radiometer, a spaceborne thermal infrared instrument for the accurate remote sensing of sea surface temperature, in operation since 1991. The design of these spaceborne sources, which operate at ≈ -10 °C and ≈ +30 °C, allows them to meet their unprecedented accuracy goal, namely a 3σ uncertainty in their brightness temperature of <0.1 K for the whole mission. This performance is empirically demonstrated in the laboratory and in flight by long-term temperature readout tests, temperature uniformity measurements, and direct emissivity measurements.     

Helium purge flow prevention of atmospheric contamination of cryogenically cooled optics on orbiting infrared telescopes

The ability of a He purge gas to protect the cryogenically cooled optics of orbiting infrared telescopes from the primary atmospheric contaminant, atomic oxygen, can be estimated by calculations simulating the He-O scattering events that would occur in the operating telescope. This paper reports results of accurate quantum mechanical calculations of the He-O differential cross sections σ(θ, E) needed in such calculations. To facilitate the use of these cross sections, a simple separable function of E and θ is also given which provides an adequate representation of σ(θ, E) for the entire range of relative collision energies studied, E = 0.02?1.66 eV.     

Layer-oriented adaptive optics for solar telescopes

First multiconjugate adaptive-optical (MCAO) systems are currently being installed on solar telescopes. The aim of these systems is to increase the corrected field of view with respect to conventional adaptive optics. However, this first generation is based on a star-oriented approach, and it is then difficult to increase the size of the field of view beyond 60-80?arc sec in diameter. We propose to implement the layer-oriented approach in solar MCAO systems by use of wide-field Shack-Hartmann wavefront sensors conjugated to the strongest turbulent layers. The wavefront distortions are averaged over a wide field: the signal from distant turbulence is attenuated and the tomographic reconstruction is thus done optically. The system consists of independent correction loops, which only need to account for local turbulence: the subapertures can be enlarged and the correction frequency reduced. Most importantly, a star-oriented MCAO system becomes more complex with increasing field size, while the layer-oriented approach benefits from larger fields and will therefore be an attractive solution for the future generation of solar MCAO systems.     

空间用斯特林制冷机的寿命评价

介绍了空间用斯特林制冷机的主要失效模式和失效机理,国内外寿命评价研究的状况和进展,分析了几种加速寿命评价方法.针对中国空间用制冷机寿命评价研究的现状,提出了加速寿命评价的一些见解和思路.     

空间红外天文观测中低温制冷系统分析

基于红外天文卫星中探测器组件和光学部分极低工作温度的需求,结合近来发射的2颗卫星(SIRTF和ASTRO-F),分析了红外天文卫星中的低温系统,给出了总体制冷方案和低温系统有效载荷示意框图,通过三级复合制冷方式,最大程度地降低超流氦用量,延长卫星工作寿命.针对超流氦制冷在空间应用时的特殊性,阐述了气液相分离、质量监测、...     

Optimized support systems for spaceborne dewars

In a long-lifetime dewar, heat loads to the cryogen fall into two distinct categories: parasitic heat leak (i.e. conduction and radiation from the vacuum shell) and internal heat loads (i.e. electrical power dissipation and telescope aperture heating in the case of cooled telescope systems). To accommodate launch loads, the cryogen tank support system of a spaceborne dewar must be stout, and heat conducted from the vacuum shell through the supports can have a large influence on cryogen loss rate. Sophisticated support systems using low conductivity composite materials for thermal optimization have consequently been developed. The most thermally efficient support system used to date in flight hardware is fibreglass/epoxy tension straps. To provide even better thermal efficiency than straps, various attempts have been made over the last two decades to develop dual support concepts in which a primary support reacts launch loads and a smaller, more thermally efficient support then holds the cold assembly in place after launch. This Paper compares predicted dewar performance for several cases using both tension straps and the best developed dual support approach, passive orbital disconnect struts (PODS). Results show that cryogen loss rates are very similar for both systems. Straps provide a slight advantage for storage of lighter cryogens such as helium and hydrogen, and PODS are slightly better for heavier cryogens such as nitrogen and oxygen. The PODS system is more complex than straps, and a flightworthy design does not yet exist. The performance of a flight system using straps is at this time more predictable than one using PODS.     

星载空间目标光电跟踪角速度伺服系统设计

设计了星载空间目标光电跟踪角速度伺服系统,它包括补偿校正环节、驱动功放环节、以光学望远镜和跟踪架为被控制对象的机械操作环节以及视轴稳定回路。选择直流力矩电机作为跟踪架驱动元件,以提高系统的跟踪精度。利用 Matlab 进行系统特性仿真的结果表明,设计的系统相角裕度为 69°,幅值裕度为 35.8dB,截止频率为 10rad/s,调节时间为 0.7s,具有良好的跟踪性能,达到了预期的要求。     

Photon folding for imaging in nonfocusing telescopes

We present a new technique--photon folding--for imaging in nonfocusing telescopes. Inspired by the epoch-folding method in timing analysis, the photon-folding technique directly provides the statistical significance of signals in images, by use of projection matrices. The technique is robust against common imaging problems such as aspect errors and a nonuniform background. The technique provides a deterministic recursive algorithm for improving images, which can be implemented on line. The higher-order photon-folding technique allows a systematic correction for coding noises, which is suitable for studying weak sources in the presence of highly variable strong sources. The technique can be applied to various types of nonfocusing telescopes such as coded-aperture optics, rotational collimators, or Fourier grid telescopes.     

Off-axis systems for 4-m class telescopes

We describe here an off-axis design for a 4.0-m astronomical telescope. We show that the geometric optical performance of this configuration can equal that of an on-axis conventional configuration while the diffractive performance fundamentally surpasses conventional telescopes because of the absence of pupil obstruction. The specific optical design described here uses a single off-axis primary mirror to obtain three distinct final focus ports: an f/10 port (with corrector) for wide-field imaging and spectroscopy with a field of view (FOV) of 15 arc min; a small-field, 2-reflection f/10 port suitable for polarimetry and coronagraphy; and a slower, f/16(3-reflection) port with a 7 arc min FOV. For general astronomical observations requiring high optical throughput and low scattered light, this design is superior to conventional Ritchey-Chretien optical configurations.     

Partial correction for turbulent distortions in telescopes

To provide complete compensation for turbulent distortions in the visible range at aperture dimensions typical for modern telescopes (6-10 m), one needs to develop adaptive systems with hundreds of control channels. More simple adaptive systems that provide complete compensation in the infrared range can give an essential advantage in angular resolution in the visible range too. In this case the image brightness characterized by the Strehl ratio remains much less than that in the diffraction-limited case, i.e., the system provides only partial compensation. We present the results of numerical calculations of the partially corrected point-spread function and discuss possible approaches to composing the adaptive system configuration.     

Short-wave infrared transfer radiometer for the calibration of the moderate-resolution imaging spectrometer and the advanced spaceborne thermal emission and reflection radiometer

A short-wave infrared (700-2500-nm) radiometer has been designed and built to calibrate and cross calibrate spherical-integrating sources used in the calibration of satellite sensors residing on NASA's Earth Observing System platforms. We describe the design, predicted and measured performance, and calibration of the transfer radiometer.     

用于微光探测器的天文杜瓦

综述了天文用ＣＣＤ微光探测器对天文杜瓦的要求，介绍了研制的ＴＷＤ型杜瓦的特点和试验情况。试验结果表明，在无探测腔时，Ⅱ型和Ⅲ型杜瓦容器的技术指标分别达到：有效容积２．５Ｌ和１．２５Ｌ；质量２．０５ｋｇ和３．０２ｋｇ；液氮保存期１１０ｈ和１１６ｈ。真空寿命达２年以上。接探测腔后，Ⅱ型杜瓦液氮保存期为４０ｈ；ＣＣＤ冷盘温度可达到－１００～－１２０℃。