“卡西尼”牵手土星

价值连城的美国大型空间探测器“卡西尼”(Cassini)在经过长达约7年、航行几十亿千米的星际历程之后，终于在2004年7月1日进入土星轨道，开始它4年的环绕飞行。大约6个月后．该探测器将释放所携带的子探测器“惠更斯”(Huygens)．它穿过浓密的大气到达土星的一个叫“泰坦”(Titan．又叫土卫6)的卫星，它们的主要任务是研究土星光环的三维结构和动力学状态．分析土星卫星的表面成分和地质史等。来自美国和欧洲的科学家将借助“卡西尼”携带的两架相机对土里的特征，卫里和光环作更深入的研究。     

“卡西尼”踏上“土星之旅”

“卡西尼”计划耗资34亿美元,遍布全球的4000多名科学家、工程技术人员将为其服务到2008年。这是一个“将一大堆鸡蛋都放在一个篮子里”的冒险之举,让我们祝它一路平安!     

“卡西尼”探测器飞往土星

1997年10月15日美国东部时间4时43分，美国航宇局的核动力空间探测器“卡西尼”（Cassin）在美国佛罗里达州的卡纳维拉尔角由大力神一4B火箭发射升空，开始了它历时7年、行程长达35X108km的土星之行。在抵达目的地土星之前，重达5．63t的“卡西尼”探测器在引力的作用下将两次掠过金星，1999年8月从9OOkm的上空掠过地球，然后掠过木星，最后于ZOO4年7月进入土星的轨道，开始对土星神秘的光环系统及它的卫星进行为期4年的考察。直探测土星的目的土星是太阳系中极富有神秘色彩的行星，它有～个彩色的光环系统环绕着，同时还有好些卫星围绕…     

采用核动力的“卡西尼”号

美国时间１９９７年１０月１５日４时４３分，重达５．６吨的美国宇航局土星探测飞船“卡西尼”号于佛罗里达卡纳维拉尔角肯尼迪航天中心用“大力神”Ⅳ型火箭发射升空，开始了长达７年的土星之旅。这次土星探测计划的正式名称为“卡西尼工程”。卡西尼是意大利１７世纪的...     

“卡西尼”之旅：揭秘土星

土星．距离太阳最近的第六颗行星。它位于木星与天王星之间，是太阳系的第二大行星。土星的直径约为地球的9．4倍，质量是地球的95倍。土星的密度是太阳系中最小的，只有水密度的70％。土星与太阳的距离大约是9～10个天文单位，每29．46个地球年围绕太阳公转一周。     

由三体问题开启的“卡西尼”之路

正2017年9月,有两件太空探索领域的大事。其中一件是在旅行者号探测器发射40周年之际,美国航空航天局为它发送了一句由很多网民投票选出的寄语:We offer friendship across the stars.You are not alone.(友谊跨越繁星,你不是孤身一人。)另一件是卡西尼号探测器完成了它的使命,已于15     

动手做个卡西尼

~~动手做个卡西尼     

再见,卡西尼

正2017年9月15日,卡西尼号探测器冲入土星大气层,结束了自己的辉煌一生。卡西尼号探测器是人类有史以来发射的第4颗土星探测器,不过它实际上是人类研制的第1颗成功环绕土星飞行的探测器。其发现的科学成果之多、运行时间之久,都非常引人注目。1997年10月15日,卡西尼探测器在美     

卡西尼掠过土卫九

卡西尼在逼近土星的途中拍下了一系列令人惊叹的高分辨率土卫九的照片，展现了这个小“月亮”伤痕累累的表面特征。大量的证据表明这个小天体主要由冰组成，表面覆盖着一层厚仅300-500米的暗色物质。     

使用深度神经网络检测Cassini ISS图像中圆盘状星体轮廓

Cassini空间探测器光学成像系统（ISS）拍摄的图像中,很多卫星呈现为面元,其轮廓检测是天体测量的重要工作.使用神经网络方法进行ISS图像中面元轮廓检测.每个ISS图像的像素分为轮廓边缘和非轮廓两类.使用神经网络框架TensorFlow,输入每个像素的9个特征,输出每个像素的分类.利用约3.6万个像素训练该网络,通过380幅ISS图像进行测试.与人工标记结果相比,轮廓像素检测的平均精确率为78.26%,平均召回率为73.32%.以检出轮廓像素作为输入,通过椭圆拟合得到面元的轮廓,所得轮廓与面元真实轮廓吻合良好.研究结果表明该方案能够有效检测出面元轮廓,进而给出假图像星的排除范围.      

Analytical pyrolysis experiments of Titan aerosol analogues in preparation for the Cassini Huygens mission.

Comparative pyrolysis mass spectrometric data of Titan aerosol analogues, called "tholins", are presented. The Titan tholins were produced in the laboratory at Cornell by irradiation of simulated Titan atmospheres with high energy electrons in plasma discharge. Mass-spectrometry measurements were performed at FOM of the solid phase of various tholins by Curie-point pyrolysis Gas-Chromatography/Mass-Spectrometry (GCMS) and by temperature resolved in source Pyrolysis Mass-Spectrometry to reveal the composition and evolution temperature of the dissociation products. The results presented here are used to further define the ACP (Aerosol Collector Pyrolyser)-GCMS experiment and provide a basis for modelling of aerosol composition on Titan and for the interpretation of Titan atmosphere data from the Huygens probe in the future.     

Space flight, microgravity, stress, and immune responses.

Exposure of animals and humans to space flight conditions has resulted in numerous alterations in immunological parameters. Decreases in lymphocyte blastogenesis, cytokine production, and natural killer cell activity have all been reported after space flight. Alterations in leukocyte subset distribution have also been reported after flight of humans and animals in space. The relative contribution of microgravity conditions and stress to the observed results has not been established. Antiorthostatic, hypokinetic, hypodynamic, suspension of rodents and chronic head-down tilt bed-rest of humans have been used to model effects of microgravity on immune responses. After use of these models, some effects of space flight on immune responses, such as decreases in cytokine function, were observed, but others, such as alterations in leukocyte subset distribution, were not observed. These results suggest that stresses that occur during space flight could combine with microgravity conditions in inducing the changes seen in immune responses after space flight. The biological/biomedical significance of space flight induced changes in immune parameters remains to be established. Grant Numbers: NCC2-859, NAG2-933.     

Turbulence,complexity, and solar flares

The issue of predicting solar flares is one of the most fundamental in physics, addressing issues of plasma physics, high-energy physics, and modelling of complex systems. It also poses societal consequences, with our ever-increasing need for accurate space weather forecasts. Solar flares arise naturally as a competition between an input (flux emergence and rearrangement) in the photosphere and an output (electrical current build up and resistive dissipation) in the corona. Although initially localised, this redistribution affects neighbouring regions and an avalanche occurs resulting in large scale eruptions of plasma, particles, and magnetic field. As flares are powered from the stressed field rooted in the photosphere, a study of the photospheric magnetic complexity can be used to both predict activity and understand the physics of the magnetic field. The magnetic energy spectrum and multifractal spectrum are highlighted as two possible approaches to this.     

论精大贵稀仪器仪表潜在功能的开发

精大贵稀仪器仪表潜在功能的开发,充分利用了现有资源,节省大量的更新经费,产生了巨大的技术、经济效益.在市场经济机制下,开展共用协作,极大地改善了精大贵稀仪器利用率低的状况,且有一定的推广应用前景,为培养、锻炼年轻的技术人员,以点带面地推动人员技术素质的全面提高起了积极的作用.     

Probable interstellar MgX (X = CN, NC, CCH, CC, C3N, NCCC, CCNC, C4H, and C4): A DFT study

The geometries, dipole moments, and rotational constants for several magnesium compounds and their anions were calculated by using the B3LYP/Aug-cc-pVTZ method. The rotational constants of linear forms have been derived to be used for laboratory experiment and astronomical observation.     

Determination of K,Ar, Cl,S, Si and Al flare abundances from RESIK soft X-ray spectra

The RESIK is a high sensitivity, uncollimated bent crystal spectrometer which successfully operated aboard Russian CORONAS-F solar mission between 2001 and 2003. It measured for the first time in a systematic way solar soft X-ray spectra in the four wavelength channels from 3.3 Å to 6.1 Å. This range includes characteristic strong lines of H- and He-like ions of K, Ar, Cl, Si, S and Al in the respective spectral channels. A distinguishing feature of RESIK is its possibility of making reliable measurements of the continuum radiation in flares. Interpretation of line and the continuum intensities observed in vicinity of respective strong lines provides diagnostics of plasma temperature and absolute abundances of K, Ar, Cl, S, Si and Al in several flares. We analyzed the observed intensities of spectral lines and the nearby continuum using the CHIANTI v5.2 atomic data package. A specific, so-called “locally isothermal” approach has been used in this respect allowing us to make not only flare-averaged abundance estimates, but also to look into a possible variability of plasma composition during the course of flares.     

Advancing participation of blind students in Science,Technology, Engineering,and Math

Like their sighted peers, many blind students in elementary, middle, and high school are naturally interested in space. This interest can motivate them to learn fundamental scientific, quantitative, and critical thinking skills, and sometimes even lead to careers in Science, Technology, Engineering, and Math (STEM) disciplines. However, these students are often at a disadvantage in science because of the ubiquity of important graphical information that is generally not available in accessible formats, the unfamiliarity of teachers with non-visual teaching methods, lack of access to blind role models, and the low expectations of their teachers and parents. We discuss joint efforts by the National Aeronautics and Space Administration (NASA) and the National Federation of the Blind’s (NFB) National Center for Blind Youth in Science (NCBYS) to develop and implement strategies to promote opportunities for blind youth in science. These include the development of tactile space science books and curriculum materials, science academies for blind middle school and high school students, and college-level internship and mentoring programs. The partnership with the NFB exemplifies the effectiveness of collaborations between NASA and consumer-directed organizations to improve opportunities for underserved and underrepresented individuals.     

Utilization of CAM,CAF, MAX,and FAX for space radiation analyses using HZETRN

To estimate astronaut health risk due to space radiation, one must have the ability to calculate various exposure-related quantities that are averaged over specific organs and tissue types. Such calculations require computational models of the ambient space radiation environment, particle transport, nuclear and atomic physics, and the human body. While significant efforts have been made to verify, validate, and quantify the uncertainties associated with many of these models and tools, relatively little work has focused on the uncertainties associated with the representation and utilization of the human phantoms. In this study, we first examine the anatomical properties of the Computerized Anatomical Man (CAM), Computerized Anatomical Female (CAF), Male Adult voXel (MAX), and Female Adult voXel (FAX) models by comparing the masses of various model tissues used to calculate effective dose to the reference values specified by the International Commission on Radiological Protection (ICRP). The MAX and FAX tissue masses are found to be in good agreement with the reference data, while major discrepancies are found between the CAM and CAF tissue masses and the reference data for almost all of the effective dose tissues. We next examine the distribution of target points used with the deterministic transport code HZETRN (High charge (Z) and Energy TRaNsport) to compute mass averaged exposure quantities. A numerical algorithm is presented and used to generate multiple point distributions of varying fidelity for many of the effective dose tissues identified in CAM, CAF, MAX, and FAX. The point distributions are used to compute mass averaged dose equivalent values under both a galactic cosmic ray (GCR) and solar particle event (SPE) environment impinging isotropically on three spherical aluminum shells with areal densities of 0.4 g/cm², 2.0 g/cm², and 10.0 g/cm². The dose equivalent values are examined to identify a recommended set of target points for each of the tissues and to further assess the differences between CAM, CAF, MAX, and FAX. It is concluded that the previously published CAM and CAF point distributions were significantly under-sampled and that the set of point distributions presented here should be adequate for future studies involving CAM, CAF, MAX, or FAX. It is also found that the errors associated with the mass and location of certain tissues in CAM and CAF have a significant impact on the mass averaged dose equivalent values, and it is concluded that MAX and FAX are more accurate than CAM and CAF for space radiation analyses.