反射式紫外天基单镜计算成像系统设计

紫外天基成像是目前对太阳观测的主要手段之一。针对紫外天基遥感对成像系统高分辨、轻量化的需求,开展了紫外天基单镜计算成像系统研究,应用“光学镜面设计”与“计算成像”相结合的思路,通过对球面、六次偶次非球面、十次偶次非球面、Q-type面、Zernike多项式面的天基反射镜成像光学系统设计,以及基于傅里叶叠层超分辨的计算成像分析,验证了该设计方法可在波长135 nm紫外光波段实现5.4°圆视场、分辨能力优于0.11 mm的设计指标。反射式六次偶次非球面具备一定的综合优势。     

太阳极紫外成像仪光学系统研制

文章针对太阳观测的物理需求,完成了角分辨率优于1″的太阳极紫外成像仪光学系统的研制。该系统采用经典卡塞格林光路结构。使用ZEMAX软件对所设计的光学系统进行分析,结果表明其在视场角±17′内的光斑均位于1个像素（13.5 μm×13.5 μm）范围内。在光学系统研制完成后,采用一种间接方法来检测光学系统角分辨率：首先利用ZYGO干涉仪检测光学系统的波像差,再根据检测的出瞳面上的波像差结果,计算出光学系统在19.5 nm工作波段的点扩散函数;结果表明,光学系统在视场角±17′的范围内,像素环围能量比均优于80%,在19.5 nm波段的角分辨率优于1″。     

Communicating across the solar system

The technological advances of the Space Age have enabled us to project our senses through complex instruments to the edge of the Solar System and beyond. The link back to Earth by the communication channel has provided us with a wealth of information. The vast improvement in communication capability, by a factor of 10¹⁸, from the launching of the first earth satellites to the capacity of the Voyager telecommunications link across the Solar System, is symbolic of both our technical prowess and our cultural development. The combination of data rate and extreme distance at the Voyager 2 encounters with Uranus and Neptune in 1986 and 1989 will require the ground network to perform an engineering feat of unequalled magnitude. This paper describes the engineering challenge of communicating with spacecraft at the limits of the Solar System and the engineering responses to that challenge.     

Impact seeding and reseeding in the inner solar system

Assuming that asteroidal and cometary impacts onto Earth can liberate material containing viable microorganisms, we studied the subsequent distribution of the escaping impact ejecta throughout the inner Solar System on time scales of 30,000 years. Our calculations of the delivery rates of this terrestrial material to Mars and Venus, as well as back to Earth, indicate that transport to great heliocentric distances may occur in just a few years and that the departure speed is significant. This material would have been efficiently and quickly dispersed throughout the Solar System. Our study considers the fate of all the ejected mass (not just the slowly moving material), and tabulates impact rates onto Venus and Mars in addition to Earth itself. Expressed as a fraction of the ejected particles, roughly 0.1% and 0.001% of the ejecta particles would have reached Venus and Mars, respectively, in 30,000 years, making the biological seeding of those planets viable if the target planet supported a receptive environment at the time. In terms of possibly safeguarding terrestrial life by allowing its survival in space while our planet cools after a major killing thermal pulse, we show via our 30,000- year integrations that efficient return to Earth continues for this duration. Our calculations indicate that roughly 1% of the launched mass returns to Earth after a major impact regardless of the impactor speed; although a larger mass is ejected following impacts at higher speeds, a smaller fraction of these ejecta is returned. Early bacterial life on Earth could have been safeguarded from any purported impact-induced extinction by temporary refuge in space.     

Missions to the outer solar system and beyond

A report on the second IAA symposium on realistic near-term advanced scientific space missions, held in Aosta, Italy, 29 June-1 July 1998. Though some might find the idea of interstellar travel far-fetched, the question it raises of the need for a space-based infra-structure and economy is pertinent to a growing number of today's activities.     

The roles of humans and robots in exploring the solar system

Historically, advocates of solar system exploration have disagreed over whether program goals could be entirely satisfied by robotic missions. Scientists tend to argue that robotic exploration is most cost-effective. However, the human space program has a great deal of support in the general public, thereby enabling the scientific element of exploration to be larger than it might be as a stand-alone activity. A comprehensive strategy of exploration needs a strong robotic component complementing and supporting human missions. Robots are needed for precursor missions, for crew support on planetary surfaces, and for probing dangerous environments. Robotic field assistants can provide mobility, access to scientific sites, data acquisition, visualization of the environment, precision operations, sample acquisition and analysis, and expertise to human explorers. As long as space exploration depends on public funds, space exploration must include an appropriate mix of human and robotic activity.     

用于高精度太阳敏感器标定的模拟光源控制系统设计

为了精确模拟空间太阳辐照方向的变化,设计了一种以计算机控制为核心的、用于高精度太阳敏感器标定的模拟光源闭环控制系统。由计算机直接控制光电隔离输出卡,所输出的数字信号经过功率驱动电路和软启动电路后实现模拟光源的开启与关闭,采用软件方式控制步进电机的转速和转向,并通过高精度光电编码器实时获取当前的转动角度值,再经串口通信反馈给计算机,构成闭环控制系统。标定测量表明:系统的俯仰角和方位角转动误差均小于0.02°,均满足高精度太阳敏感器标定对模拟光源的要求。     

太阳系小天体表面环境综述

地面和空间望远镜观测,特别是最近30多年来的历次深空探测任务极大提高了我们对太阳系小天体的认识。现已知小天体表面具有复杂多样的形貌特征,这些特征与其历史上所经历过的地质演变有密切关系,亦可为理解早期太阳系的动力学环境提供重要信息。文章首先简要介绍了通过天文观测数据反演小行星形貌信息的基本原理和方法;然后基于已实施的深空探测任务获取的数据资料,回顾和总结了433 Eros、25143 Itokawa、4179 Toutatis、162173 Ryugu、101955 Bennu及486958 2014 MU69这6颗小行星的表面环境和物理性质,其中着重介绍了对这几颗小行星的形状、表面碎石形态和分布、撞击坑形貌和分布、表面坡度、沟槽和山脊等线性结构以及表壤运动痕迹等的认识,以及如何根据这些信息推测各小行星的形成历史;最后简要介绍了目前认为可能影响小行星表面形貌的几种机制,以期为我国即将开展的小天体深空探测任务提供借鉴。     

Detection technique for artificially illuminated objects in the outer solar system and beyond

Existing and planned optical telescopes and surveys can detect artificially illuminated objects, comparable in total brightness to a major terrestrial city, at the outskirts of the Solar System. Orbital parameters of Kuiper belt objects (KBOs) are routinely measured to exquisite precisions of<10(-3). Here, we propose to measure the variation of the observed flux F from such objects as a function of their changing orbital distances D. Sunlight-illuminated objects will show a logarithmic slope α ≡ (d log F/d log D)=-4, whereas artificially illuminated objects should exhibit α=-2. The proposed Large Synoptic Survey Telescope (LSST) and other planned surveys will provide superb data and allow measurement of α for thousands of KBOs. If objects with α=-2 are found, follow-up observations could measure their spectra to determine whether they are illuminated by artificial lighting. The search can be extended beyond the Solar System with future generations of telescopes on the ground and in space that would have the capacity to detect phase modulation due to very strong artificial illumination on the nightside of planets as they orbit their parent stars.     

基于紫外ICCD的导弹逼近告警系统研究

在200-400nm紫外波段,阳光辐射被大气中的臭氧层强烈吸收,存在所谓的“太阳光谱盲区”;而背景环境中景物的温度不足以产生有影响的紫外辐射。因此,在低空环境中,紫外探测器很容易探测到微弱的紫外辐射,具有很低的虚警率。开展了基于紫外ICCD的导弹逼近告警系统研究、紫外目标特性及大气传输研究、大视场窄带紫外光学系统研究及紫外图像处理等研究,进行了各种测试试验,取得了预期的研究成果。     

An alternative approach to solar system exploration planning

Planning for the future exploration of the solar system has involved the structuring of a series of missions that address major scientific objectives at a minimum runout cost for the entire endeavor. In many cases, however, the optimal structuring of a program that would minimize the runout cost would entail an unacceptable high annual funding. Our actual planning must consider the planning wedge imposed on the National Aeronautics and Space Administration. It is vital that a plan be structured that copes with the annual restraint. If we do not recognize this, our plan will not be realized and a queing problem will result, thus negating all of our planning efforts.This paper presents ideas as to how planetary initiatives can be structured, wherein the peak annual funding is minimized. One vital aspect in the plan is to have a transportation capability that can launch a mission in any planetary opportunity. Solar electric propulsion can provide this capability. Another cost reduction approach would be to structure a mission set in a time sequenced fashion that could utilize essentially the same spacecraft for the implementation of several missions. This opportunity does exist. A third technique would be to fulfill a scientific objective in several sequential missions rather than attempt to accomplish all of the objectives with one mission. This approach might be applied to a mission currently in the planning stage designated the Saturn Orbiter Dual Probe mission. The current concept involves the delivery of a Saturn probe, a Titan probe, and a Saturn Orbiter by a one Shuttle launch. In this case, the orbiter must serve as a relay station for both probes; map the magnetosphere of Saturn; conduct a survey of Saturn's major satellites; and perform the planetological observation of Saturn itself. This mission entails the development of a complex spacecraft that would be required to have a fairly long life due to the extended mission operations at the benefit of accomplishing the mission with one launch. An alternate approach would be to break the mission into two separate elements. We could, for example, launch a Saturn orbiter carrying a Saturn entry probe. After serving as a communications relay system for the Saturn probe, the orbiter would then be specialized to map the magnetosphere of Saturn. A second launch would involve the delivery of a Titan probe by another orbiter where after delivery the orbiter would conduct the planetological observation of Saturn and its satellites. For the split-launch option, the runout cost for the two missions would be greater than the single launch option. However, optimum structuring of the two missions could materially reduce the peak annual funding.This paper presents data on the estimated cost on a year by year basis of a mission set structured to minimize the runout cost with no concern as to the peak annual funding as compared to a mission set that would yield the same scientific objectives in a slightly longer time span wherein the annual peak funding would be minimized. The consequences of this revised plan are analyzed.     

太阳能热推进系统效率分析

太阳能热推进采用小分子量气体作为推进剂可以获取800～900 s高比冲,但提高推进系统的换热效率是目前亟待解决的问题.本研究建立了太阳能热推进系统主要部件的基本分析模型,在利用有限单元法进行热分析的基础上,对系统在多种工况下的相关参数进行了计算,分析了各部件主要参数对提高太阳能热推进系统热效率和推进效率的影响,得出了系统效率在不同工作状态下的变化规律,并提出了提高系统效率的措施.     

面向太阳系边际探测的激光通信方案研究

针对我国太阳系边际探测任务需求,提出了利用激光链路进行对地高速信息传输的方案。梳理了深空激光通信的国外发展现状,分析了太阳系边际探测任务的激光链路特点和约束条件,给出了飞行激光终端和激光地面站的初步方案和主要参数,进行了链路预算和影响因素分析,并对我国未来太阳系边际探测任务激光通信的发展进行展望,为我国太阳系边际探测任务的激光通信论证与实施提供参考。     

Space station — the new frontier

The exciting challenge of building a permanent space station has been taken up by the USA, and participation in its development has been offered to the USA's allies. European countries are faced with the dilemma of whether to cooperate or to try to develop an autonomous approach. This article discusses the opportunities for Europe in participating closely in the US project — particularly in providing pressurized modules based on the Columbus programme — and argues that it is an opportunity not to be missed.     

The telemedicine frontier: going the extra mile

Telemedicine has the potential to have a greater impact on the future of medicine than any other modality and will profoundly alter the medical landscape of the twenty-first century. In the most remote areas, it can bring high-quality health care where none is now available. In global health care, it can enhance and standardize the quality of medical care, including developing countries. In the realm of space flight, it can provide a lifeline to medical expertise and monitoring. Through its mobility, it can provide urgently needed health care in instances of natural disaster. However, a number of challenges exist in its coordination and implementation on a global scale, specifically in the international and remote disaster scenarios. In the area of spaceflight, telemedicine capability will remain a consultation/information ‘lifeline’, but additional onboard medical capability and expertise will become crucial complements as missions become more advanced and remote from Earth.     

Ascending flows in the solar atmosphere and formation of the solar wind

Some morphological features of solar magnetic fields in the chromosphere and corona are considered based on studying various observational data. These data are compared to the results of observation of the solar wind and interplanetary magnetic field, as well as to the data on fluxes of solar cosmic rays. New specific features are found in the solar wind structure, and new additional indications of sources of the solar wind are obtained. The properties of the active regions and coronal holes are considered. A model of the ascending stream-like plasma flow is suggested. It flows around the discrete arched magnetic field tubes in the solar atmosphere and stretches them out into interplanetary space.     

Sky distribution of artificial sources in the galactic belt of advanced cosmic life

In line with the concept of the galactic belt of advanced life, we evaluate the sky distribution of detectable artificial sources, using a simple astrophysical model. The best region to search is the median band of the Milky Way in the Vulpecula-Cygnus region, together with a narrower one in Carina. Although this work was done in view of a proposal to send a SETI probe at a gravitational focus of the Sun, we recommend these sky regions particularly for the searches of the sky survey type.     

空间辐射场中高能Fe离子微剂量学分析

Fe离子是空间辐射场中备受关注的重离子之一,其等效剂量、生物效应等构成载人航天的主要危险。文章通过计算等效组织正比计数器对高能Fe离子的响应,模拟其在等效组织中的线能微剂量学量。计算得到的结果与实验结果基本符合,偏差不超过10%;在此基础上,考虑TEPC(组织等效正比计数器)对银河宇宙射线中能量范围在90～1000 MeV/u的Fe离子的响应,得到其线能量为80～600keV/μm,最大值在100～150keV/μm之间;通过公式计算得到100～200keV/μm线能量对应的射线品质因数高于25,将产生相当高的生物效应。     

Radioisotope electric propulsion of sciencecraft to the outer solar system and near-interstellar space

Recent results are presented in the study of radioisotope electric propulsion as a near-term technology for sending small robotic sciencecraft to the outer Solar System and near- interstellar space. Radioisotope electric propulsion (REP) systems are low-thrust, ion propulsion units based on radioisotope electric generators and ion thrusters. Powerplant specific masses are expected to be in the range of 100 to 200 kg/kW of thrust power. Planetary rendezvous missions to Pluto, fast missions to the heliopause (100 AU) with the capability to decelerate an orbiter for an extended science program and prestellar missions to the first gravitational lens focus of the Sun (550 AU) are investigated.