Spacecraft Equipped with a Space Debris Removal System (Aerothermodynamics,Bulk–Mass Characteristics and Trajectories of Spacecraft Descent from Near-Earth Orbits)

The processes of space debris formation are described; the urgency of the problem of its removal from near-Earth space is noted. A method to prevent the clogging of space by equipping a spacecraft to be launched into orbit with additional devices, simple in design and mode of operation, is presented. The results of the estimation of aerothermodynamics, bulk–mass characteristics and trajectories of low-orbit spacecraft equipped with a space debris disposal system are presented.     

Stellar sources in the isogal inner galactic bulge field (l=0°,b= − 1°)

ISOGAL is a survey at 7 and 15 μm with ISOCAM of the inner galactic disk and bulge of our Galaxy. The survey covers ∼ 22 deg² in selected areas of the centrall = ±30 degree of the inner Galaxy. In this paper, we report the study of a small ISOGAL field in the inner galactic bulge (l = 0°,b = −1°, area = 0.033deg²). Using the multicolor nearinfrared data (IJK_s) of DENIS (DEep Near Infrared Southern Sky Survey) and mid-infrared ISOGAL data, we discuss the nature of the ISOGAL sources. The various color-color and color-magnitude diagrams are discussed in the paper. While most of the detected sources are red giants (RGB tip stars), a few of them show an excess in J-K_s and K_s-[15] colors with respect to the red giant sequence. Most of them are probably AGB stars with large mass-loss rates.     

The coronal disturbance (W 90 °, N 25 °) in the eclipse spectra of July 31, 1981

The physical properties in the coronal disturbance (CD) (W90, N25°) associated with an active prominence are investigated on the basis of the intensities and profiles of 5694 Å Caxv and 6702 Å Nixv lines and continuum measured in the eclipse coronal spectra of 31 July, 1981. The spectrograms have been taken with a dispersion of between 7 to 10 Å mm^-1 and a solar image of 15 mm in diameter. The following characteristics of the CD have been deduced. The CD occurred cospatially with an active prominence and consisted of two discrete regions with different temperatures penetrating each other. (1) Caxv region: T _e= 3.8 × 10⁶ K, the length along the slit of the spectrograph Z 65000 km, the effective line-of-sight length L 20000 km, the average electron density , nonthermal velocities V _t= (20–32) km s^-1. (2)Nixv-Caxiii region: T _e= 2.3 × 10⁶ K, Z 37000 km, L 35000 km, n _e 1 × 10⁹ cm^-3, V _t= (23–30) km s^-1. A macroscopic mass motion has been discovered within the Nixv region of the CD from the Doppler shifts of the 6702 Å Nixv line: V _r= + 27 km s^-1 on the lower and V _r= - 12 km s^-1 on the upper border of the CD. The average height of the CD was H 0.08 R . The radial velocities in the prominence found from the emission line tilts are + 12 and - 8 km s^-1 on its lower and upper borders. A similar picture of the mass motion in the CD and the prominence speaks in favour of an intimate relation between them.     

Spacecraft Doppler tracking with possible violations of LLI andLPI： a theoretical modeling

Currently two-way and three-way spacecraft Doppler tracking techniquesare widely used and play important roles in control and navigation of deep space mis-sions. Starting from a one-way Doppler model, we extend the theory to two-way andthree-way Doppler models by making them include possible violations of the localLorentz invariance （LLI） and the local position invariance （LPI） in order to test theEinstein equivalence principle, which is the cornerstone of general relativity and allother metric theories of gravity. After taking the finite speed of light into account,which is the so-called light time solution （LTS）, we make these models depend on thetime of reception of the signal only for practical convenience. We find that possibleviolations of LLI and LPI cannot affect two-way Doppler tracking under a linear ap-proximation of LTS, although this approximation is sufficiently good for most cases inthe solar system. We also show that, in three-way Doppler tracking, possible violationsof LLI and LPI are only associated with two stations, which suggests that it is betterto set the stations at places with significant differences in velocities and gravitationalpotentials to obtain a high level of sensitivity for the tests.     

Engineering Methodology for Assessment оf Spacecraft Structure Shock Load Levels During Pyromechanical Separation

In this paper, we consider an algorithm for estimating the dynamic shock loads on sensitive units, assemblies, systems, and payloads of a spacecraft, as well as on precision elements of its construction occurring near separation belts that are based on linear cumulative and noncumulative pyromechanisms.     

Spacecraft trajectories to the L<Subscript>3</Subscript> point of the Sun–Earth three-body problem

Of the three collinear libration points of the Sun–Earth Circular Restricted Three-Body Problem (CR3BP), L₃ is that located opposite to the Earth with respect to the Sun and approximately at the same heliocentric distance. Whereas several space missions have been launched to the other two collinear equilibrium points, i.e., L₁ and L₂, taking advantage of their dynamical and geometrical characteristics, the region around L₃ is so far unexploited. This is essentially due to the severe communication limitations caused by the distant and permanent opposition to the Earth, and by the gravitational perturbations mainly induced by Jupiter and the close passages of Venus, whose effects are more important than those due to the Earth. However, the adoption of a suitable periodic orbit around L₃ to ensure the necessary communication links with the Earth, or the connection with one or more relay satellites located at L₄ or L₅, and the simultaneous design of an appropriate station keeping-strategy, would make it possible to perform valuable fundamental physics and astrophysics investigations from this location. Such an opportunity leads to the need of studying the ways to transfer a spacecraft (s/c) from the Earth’s vicinity to L₃. In this contribution, we investigate several trajectory design methods to accomplish such a transfer, i.e., various types of two-burn impulsive trajectories in a Sun-s/c two-body model, a patched conics strategy exploiting the gravity assist of the nearby planets, an approach based on traveling on invariant manifolds of periodic orbits in the Sun–Earth CR3BP, and finally a low-thrust transfer. We examine advantages and drawbacks, and we estimate the propellant budget and time of flight requirements of each.     

> 25 MeV Proton Events Observed by the High Energy Telescopes on the STEREO A and B Spacecraft and/or at Earth During the First ∼ Seven Years of the STEREO Mission

Using observations from the High Energy Telescopes (HETs) on the STEREO A and B spacecraft and similar observations from near-Earth spacecraft, we summarize the properties of more than 200 individual >?25 MeV solar proton events, some detected by multiple spacecraft, that occurred from the beginning of the STEREO mission in October 2006 to December 2013, and provide a catalog of these events and their solar sources and associations. Longitudinal dependencies of the electron and proton peak intensities and delays to onset and peak intensity relative to the solar event have been examined for 25 three-spacecraft particle events. Expressed as Gaussians, peak intensities fall off with longitude with σ=47±14^° for 0.7?–?4 MeV electrons, and σ=43±13^° for 14?–?24 MeV protons. Several particle events are discussed in more detail, including one on 3 November 2011, in which ～?25 MeV protons filled the inner heliosphere within 90 minutes of the solar event, and another on 7 March 2012, in which we demonstrate that the first of two coronal mass ejections that erupted from an active region within ～?1 hour was associated with particle acceleration. Comparing the current Solar Cycle 24 with the previous cycle, the first >?25 MeV proton event was detected at Earth in the current solar cycle around one year after smoothed sunspot minimum, compared with a delay of only two months in Cycle 23. Otherwise, solar energetic particle event occurrence rates were reasonably similar during the rising phases of Cycles 23 and 24. However, the rate declined in 2013, reflecting the decline in sunspot number since the peak in the northern-hemisphere sunspot number in November 2011. Observations in late 2013 suggest that the rate may be rising again in association with an increase in the southern sunspot number.     

小行星(215)、(323)、(416)和(432)的轨道改进

这四颗小行星的历元很早,都是在二、三十年以前.由于多年未算摄动,轨道逐渐偏离,观测与计算间差值。O—C 已增大到一度以上.鉴于改进轨道、计算准确冲日星历表的迫切需要,1962年冬季在已利用电子计算机算得木星、土星精确摄动的基础上,我们搜集了近几年的观测资料,对此四颗星作了轨道改进.轨道改进的计算系根据爱克尔和勃劳威尔(Eckert and Brouwer)的直角座标的方法.为避免小偏心率和大倾角情况对精确度的影响,使能比较确定地求得方程式的解,我们采用下列方程系统:     

从零开始(六)

这次让我们来制作一件能更加形象化展示天象的天文小制作——星座图转盘。一般星图上的星座图基本上都是点与连线的组合,而我们这次要做的星座图转盘上面的每一个星座,全部都是一个个具体的星座想象图。它们是一年四季最主要的星座:有春夜的狮子     

从零开始(一)

这是今年《天文爱好者》专为初学天文的读者开辟的一个栏目,名字叫“从零开始”。有许多小朋友,当然也有不少大朋友,特别是那些教小朋友的老师们,说不定还有许多年纪大的老人家,很想了解一些关于星星和星座、昼夜和四季的天文知识,想听听关于星星的神话传说。本栏目就是要满足这些读者的要求,给大家介绍怎样在密密麻麻的繁星中将一个个星座、一颗颗行星辨认出来,给大家讲讲星星的天文知识、星座的神话传说。不同季节天上的星座和亮星。怎样看星星辨方向。特别还要介绍几种看星测时的方法。“从零开始”还要教给大家几种天文爱好者特别感兴趣的技法,譬如在短短的30秒钟内通过心算,告诉人们天上有什么星座:用不着计算就可以预报大行星在黄道星座之间的位置和运行动态。当然,要进行这项工作,首先得亲手制作一件预报行星动态的天文仪器纸上小制作,本栏目以后会刊登它的制作图纸的。像这样的小天文仪器还有南北星斗仪等多件。此外,还有演示天体运动,如地球运动、月亮圆缺的小仪器和节气日晷等。这里要说明的是,该栏目更注重用肉眼目视观测星空。因为人眼视野辽阔,望远镜视场再大。也容不下最小的星座所包含的那一片星空。     

从零开始(五)

现在让我们制作一件专门为初学天文的爱好者设计的天文小仪器——南北星斗仪。它包括一年四季所有主要星座,可以用来演示一年中任意日期,任何时刻天上有哪些星座,还可以用来直观地看星测时。南北星斗仪的制作方法1.剪下6个零件,刻出零件 N1上的大圆孔和 N2上的小圆孔。2.将 N3与 N4背靠背粘合起来,粘合时注意将二者的圆周边缘和定位小缺口准确对齐。     

The comparison of H_2CO(1_(10)–1_(11)),C~(18)O(1–0) and the continuum towards molecular clouds

We present large scale observations of C18O(1–0) towards four massive star forming regions: MON R2,S156,DR17/L906 and M17/M18. The transitions of H2CO(110–111),C18O(1–0) and the 6 cm continuum are compared in these four regions. Our analysis of the observations and the results of the Non–LTE model shows that the brightness temperature of the formaldehyde absorption line is strongest in a background continuum temperature range of about 3 – 8 K. The excitation of the H2 CO absorption line is affected by strong background continuum emission. From a comparison of H2 CO and C18 O maps,we found that the extent of H2 CO absorption is broader than that of C18 O emission in the four regions. Except for the DR17 region,the maximum in H2 CO absorption is located at the same position as the C18 O peak. A good correlation between intensities and widths of H2 CO absorption and C18 O emission lines indicates that the H2 CO absorption line can trace the dense,warm regions of a molecular cloud. We find that N(H2CO) is well correlated with N(C18O) in the four regions and that the average ratio of column densities is N(H2CO)/N(C18O) ～ 0.03.     

太阳日冕环的运动(Ⅰ)、(Ⅱ)

几年以前天空实验室的观测发现太阳日冕中多数瞬变过程是以环状形式发生质量喷射,并且测得环状瞬变过程前导边缘是加速运动或者是等速运动。这些日冕环是细长的环。环中的磁能密度大约是热能密度的十倍。观测表明:磁场是控制日冕环的主要因素。     

Solar Heii(304 Å) and Si xi(303 Å) line profiles

Additional observations of He ii (304 Å) and Si xi (303 Å) were obtained from a high resolution rocket spectrograph flown on 30 August, 1973 and 20 January, 1975. The profile of the He ii (304 Å) line is everywhere clearly non-gaussian across the solar disk, except in bright active areas. Near the limb, the profile is distinctly reversed. The profile of the Si xi (303 Å) line is essentially gaussian for all regions across the solar disk. Measurements of the He ii/Si xi intensity ratio indicate that the average value of this ratio across the disk depends markedly on solar activity, being about 101 for a moderate level of activity and 301 for a quiet Sun.     

行星环(Ⅱ)

本文评述了有关土星环的七个方面的理论研究:(1)东-西不对称性;(2)粒子大小分布;(3)环的稳定性;(4)环缝的共振起源;(5)密度波和挠曲波;(6)轮辐结构;(7)F环。 还评述了天王星环以及行星环中的碰撞、光度理论和起源等问题的研究。     

行星环(Ⅰ)

本文是关于行星环的现有观测资料的总结。     

流星观测(一)

记得F4有一首歌叫“流星雨”,歌词很煽情:“温柔的天空,应该让你感动,我在你身后,为你布置一片天空……陪你去看流星雨落在这地球上,让你的泪落在我肩膀……”如果在一个晴朗的夜晚,约上两三好友,或聚屋顶,或聚球场,更为潇洒一点,或去郊外空旷的草地、山顶,在这首缠绵悱恻的“流星雨”的浅吟低唱中,各自凝视一方的天空,守侯一闪即逝的流星的出现,岂不是一件很惬意的事民间一直有这样一个说法,如果你在流星还没有消失之前许下一个心愿,这个心愿就一定能够实现。当然,这只是一种美好的愿望,但作为一种生活的点缀,也可以为守望星空的我们增添几分浪漫的情趣。流星是飘浮在宇宙空间的尘粒,受到地球引力的影响,飞向地球,与地球大气摩擦燃烧的现象。流星的高度通常以     

星系传奇(二)

你来我往:为方便大家阅读英文资料并逐步熟悉科研前沿,我将尽可能把涉及到的基本专业术语以及关键词汇的英文标注在括号里,如果大家对此有不同意见,欢迎您与我联系:dnchen@bjp.org.cn     

探秘火星(三)

Q1哪个探测器将深入到火星地下探测?几十年来,人类一直对火星进行探索,之前登陆火星的探测器,如勇气号、机遇号、好奇号等,都是探测火星表面上的火山、峡谷、岩石、土壤的演变历史。只探测地表特征,是无法了解火星早期的演化情况的,因为包含此种信息的样品都深埋于火星地表之下。     

追逐类星体(27) 黑洞——类星体的发电机(5)

黑洞也可以蒸发天文学的发展遵循着一条规律:观测、理论、再观测、再理论……这大概也是任何一门自然科学的发展规律,只不过天文学表现得更为突出,而在漫长的发展过程中,观测又始终是天文科学的真谛。因此,天文学又被称为是一门观测的科学。黑洞的观测证据越来越丰富,黑洞对宇宙的威胁也越来越严重。理论天文学家必须出来释疑,让黑洞不仅能吃进去,还要吐出来。吐出来的困难在于黑洞的引力太强,在黑洞的视