中国地区天文夜晴空概率分布

利用１９９５￣１９９７年静止气象卫星（ＧＭＳ）红外通道的数据,采用综合了时间判断法,空间判断法和红外阈值法等特征的一种综合判断有云无云的方法,统计分析了中国地区较高空间分辨率（优于２０ｋｍ）和时间分辨率（优于１ｈ）的晴空概率和天夜晴空概率的分布。分析结果表明,全年天夜晴空概率的极限值出现在我国的西部和北部,冬半年的最大天夜晴空概率值大于夏半年。其中西藏地区１２月的天夜晴空概率可达到９５％。     

开展我国云量分布的卫星资料统计研究的建议

收集连续三年每小时的静止卫星红外云图，用温度阈值法判断有云或晴空，从而统计出我国全国范围中２０×２０ｋｍ２网格上晴天和云量分布概率，以供天文台选址参考。     

姚安天文观测站的夜间红外云量特征分析

云对天文观测具有重要影响,云量是衡量天文台址质量的重要指标.位于姚安天文观测站的红外云量仪,用于获取实时的全天高空间分辨率云图.结合空间碎片的实际观测,严格按照天文夜对累积1yr(2015-08-01—2016-07-31)的夜间云量数据进行统计和分析.姚安站的年平均夜间云量为4.42成,年天文可用夜为236个,其中测光夜98个,半测光夜44个,光谱夜94个.云量具有明显的两季特征:5月至10月间为雨季,云量显著增多,其中7月份观测条件最差;11月至次年4月为旱季,云量较少,每月的天文可用夜均在23个以上,其中1月份的测光夜最多,3月份的天文可用夜最多.结合云层对天文观测的威胁程度,统计不同云量的总时间和每月的云量分布情况,评估观测站的气象条件,为合理安排观测计划提供参考.     

红外空间天文台

上一期我们讲了红外天文卫星（IRAS）和它巨大的科学成就。这一期我们将要介绍的是IRAS之后另一个重要的红外空间项目——欧洲空间局（ESA）的红外空间天文台（Infrared Space Observatory,简称ISO）.     

日本早期的空间红外天文学

与前几期所介绍的那些大个头空间望远镜相比,今天将要出场的主人公无疑是一个小字辈,它是日本的第一个空间红外设备——空间红外望远镜（Infrared Telescope in Space,IRTS）。可能大家都注意到了,很多空间设备的名字都很相似,比如先前讲过的红外天文卫星（IRAS）、红外空间天文台（ISO）以及今天将要提到的空间红外望远镜（IRTS）,它们的名字都是大同小异。     

我国天文气候特点及潜在（光学／红外）优良台址探讨

收集了我国１９７８─１９８６年和１９９０年，共１０年时间的１９２个地面气象站每天四次总云量的观测资料，分别计算了北京时间０８ｈ，０２ｈ和０８ｈ以及２０ｈ，０２ｈ和０８ｈ的无云概率。分析结果表明：我国所处的天文气候条件的大环境并非是世界上最好的，但在国内相对较好的区域里，精心挑选出受局部地形影响形成的较好台址还是有可能的。     

小型激光天文动力学空间计划概念

小型激光天文动力学空间计划是：使用在太阳轨道上天拖曳航天器和地面站以激光干涉和脉冲测距的方法，精确地探讨天文动力学，检测相对论与时空基本定律，改进探测引力波的灵敏度以及更准确地测定太阳，行星和小行星的参数。1969年开始的月球激光（反射）测距，对地球物理，参考坐标的选定，相对论的检验均有重要的贡献。30年来，激光技术的长足进步，使现在正是适合于开始进行研究空间有源（主动）测距和光波空间通讯的时候。激光正是适合于开始进行研究空间有源（主动）测跑和光波空间通讯的时候。激光天文动力学的兴起是必然的趋势，其精确度将比现在提高3到6个数量级，将是天文动力学革命性的发展。小型激光天文动力学空间计划可以起到带头作用。它的关键技术有三，即：弱光锁相，极精确无拖曳航天和高衰减日冕仪。弱光锁相已有长足的进步。对高衰减日冕仪的研究，也有初步的方案。LISA空间计划将于2006年8月发射SMART－2，研究测试极精确地拖曳航天。小型激光天文动力学空间计划的关键技术已日趋成熟。在第一届国际激光天文动力学研讨会（2001，9．13－23）中介绍了各相关学科背景及前沿研究，讨论了激光天文动力学空间计划科学目标及相关技术，并召开了两次小型激光天文动力学空间计划预研究筹备会，建立了和欧洲的合作关系。会后着手进行此项对基础物理，太阳系探索及引力波天文学有重要科学价值的空间计划预研究。     

对高美古选址云量观测可靠性的讨论

通过对新月和满月夜期间测光夜数和云量统计数的比较, 高美古的天文测光夜数和可用夜数与丽江县的气象晴日数的比较, 以及在同样的观测时间高美古和丽江县云量观测值的比较, 本文对高美古选址云量观测可靠性的有关方面进行了讨论     

我国天文气候特点及潜在（光学／红外）优良台址探讨

收集了我国１９７８－１９８６年和１９９０年，共１０年时间的１９２个地面气象站每天四次总云量的观测资料，分别计算了北京时间０８ｈ，０２ｈ和０８ｈ以及２０ｈ，０２ｈ和０８ｈ的无云概率，分析结果表明：我国所处的天文气候条件的大环境并非是世界上最好的，但在国内相对较好的区域里，精心挑同受叶形得影响形成的较好台址还是有可能的。     

斯皮策空间望远镜

斯皮策空间望远镜（Spitzer Space Telescope,SST）是现役口径最大的红外望远镜之一。可能是出于担心与我们国家的空间太阳望远镜混淆（Space Solar Telescope）,所以在国内一般简称其为Spitzer,我们下面也将这样称呼它。它是继红外天文卫星（IRAS）之后美国宇航局（NASA）的又一个红外线望远镜。     

The artificial night sky brightness mapped from DMSP satellite Operational Linescan System measurements

We present a method to map the artificial sky brightness across large territories in astronomical photometric bands with a resolution of approximately 1 km. This is of use in quantifying the situation regarding night sky pollution, recognizing potential astronomical sites and allowing future monitoring of trends. The artificial sky brightness present in the chosen direction at a given position on the surface of the Earth is obtained by the integration of the contributions produced by every surface area in the surroundings . Each contribution is computed via detailed models for the propagation in the atmosphere of the upward light flux emitted by the area. The light flux is measured with top-of-atmosphere radiometric observations made by the Defense Meteorological Satellite Program (DMSP) Operational Linescan System.
We have applied the described method to Europe, obtaining maps of artificial sky brightness in the V and B bands.     

MACHETE: A transit imaging atmospheric Cherenkov telescope to survey half of the very high energy γ-ray sky

Current imaging atmospheric Cherenkov telescopes for very high energy γ-ray astrophysics are pointing instruments with a field of view up to a few tens of sq deg. We propose to build an array of two non-steerable (drift) telescopes. Each of the telescopes would have a camera with a FOV of 5 × 60 sq deg oriented along the meridian. About half of the sky drifts through this FOV in a year. We have performed a Monte Carlo simulation to estimate the performance of this instrument. We expect it to survey this half of the sky with an integral flux sensitivity of ∼0.77% of the steady flux of the Crab Nebula in 5 years, an analysis energy threshold of ∼150 GeV and an angular resolution of ∼0.1°. For astronomical objects that transit over the telescope for a specific night, we can achieve an integral sensitivity of 12% of the Crab Nebula flux in a night, making it a very powerful tool to trigger further observations of variable sources using steerable IACTs or instruments at other wavelengths.     

A daytime measurement of the lunar contribution to the night sky brightness in LSST’s <Emphasis Type="Italic">ugrizy</Emphasis> bands–initial results

We report measurements from which we determine the spatial structure of the lunar contribution to night sky brightness, taken at the LSST site on Cerro Pachon in Chile. We use an array of six photodiodes with filters that approximate the Large Synoptic Survey Telescope’s u, g, r, i, z, and y bands. We use the sun as a proxy for the moon, and measure sky brightness as a function of zenith angle of the point on sky, zenith angle of the sun, and angular distance between the sun and the point on sky. We make a correction for the difference between the illumination spectrum of the sun and the moon. Since scattered sunlight totally dominates the daytime sky brightness, this technique allows us to cleanly determine the contribution to the (cloudless) night sky from backscattered moonlight, without contamination from other sources of night sky brightness. We estimate our uncertainty in the relative lunar night sky brightness vs. zenith and lunar angle to be between 0.3–0.7 mags depending on the passband. This information is useful in planning the optimal execution of the LSST survey, and perhaps for other astronomical observations as well. Although our primary objective is to map out the angular structure and spectrum of the scattered light from the atmosphere and particulates, we also make an estimate of the expected number of scattered lunar photons per pixel per second in LSST, and find values that are in overall agreement with previous estimates.     

Using Laser Beacons for Daytime Adaptive Optics

This article examines the use of Laser Beacons for daytime astronomical observations. There are two potential applications: the diffraction limited observation of (1) the structure in the solar corona at all wavelengths, and (2) non-solar astronomical objects in the thermal infrared part of the spectrum. We examine the brightness of the Laser Beacon required as well as the limitations imposed by the daytime sky brightness and sky/telescope thermal emission on the observable magnitude limits. For both applications the use of Laser Beacon adaptive optics in daytime results in important research opportunities.     

Meteorological conditions at the Caucasus Observatory of the SAI MSU from the results of the 2007–2015 campaign

Based on the measurements performed from 2007 to 2015 at the summit of Mount Shatdzhatmaz adjacent to the 2.5-m telescope at the Caucasus Observatory of the SAI MSU, we have determined the statistical characteristics of basic meteorological parameters: the ambient air temperature, the ground wind speed, and the relative humidity. The stability of these parameters over the entire period of our measurements and their variations within an annual cycle have been studied. The median temperature on clear nights is +3.2°C, although there are nights with a temperature below ?15°C. The typical ground wind speed is 3 m s^?1; the probability of a wind stronger than 10 m s^?1 does not exceed 2%. The losses of observing time due to high humidity are maximal in the summer period but, on the whole, are small over a year, less than 10%. We have estimated the absolute water vapor content in the atmosphere, which is especially important for infrared observations. Minimum precipitablewater vapor is observed in December–February; the median value over these months is 5 mm. We additionally provide the wind speeds at various altitudes above the ground (from 1 to 16 km) that we obtained when measuring the optical turbulence. We present the results and technique of our measurements of the annual amount of clear night astronomical time, which is, on average, 1320 h, i.e., 45% of the possible one at the latitude of the observatory. The period from mid-September to mid-March accounts for about 70% of the clear time. A maximum of clear skies is observed in November, when its fraction reaches 60% of the possible astronomical night time.     

Near-infrared sky background fluctuations at mid- and low latitudes

The emission of the upper atmosphere introduces an additional variable component into observations of astronomical objects in the NIR 700–3,000 nm range. The subtraction of this component is not easy because it varies during the night by as much as 100% and it is not homogeneous over the sky. A program aimed at measuring and understanding the main characteristics of the atmospheric NIR emission was undertaken. A 512?×?512 CCD camera equipped with a RG780/2 mm filter is used to obtain images of the sky in a 36°?×?36° field of view. The intensities of a given star and of the nearby region devoid of star in a 439 arcmin² area are monitored during periods of time of several hours. The sky intensity measured in the 754–900 nm bandpass, reduced to zenith and zero airmass is comprised between mag20 and mag18.5 per arcsecond². A diminution by a factor of two during the night is frequently observed. Intensity fluctuations having an amplitude of 15% and periods of 5–40 min are present in the images with a structure of regularly spaced stripes. The fluctuations of the NIR sky background intensity are due to (1) the chemical evolution of the upper atmosphere composition during the night and (2) dynamical processes such as tides with periods of 3–6 h or gravity waves with periods of several tens of minutes. We suggest that a monitoring of the sky background intensity could be set up when quantitative observations of astronomical objects require exposure times longer than ~10 min. The publication is illustrated with several video films accessible on the web site http://www.obs-besancon.fr/nirsky/. Enter username: nirsky and password: skynir.     

Wide-field optical monitoring with Mini-MegaTORTORA (MMT-9) multichannel high temporal resolution telescope

We describe the properties of Mini-MegaTORTORA (MMT-9) nine-channel wide-field optical sky monitoring system with subsecond temporal resolution. This instrument can observe sky areas as large as 900 deg², perform photometry in three filters close to Johnson BV R system and polarimetry of selected objects or areas with 100–300 deg2 sizes. The limiting magnitude of the system is up to V = 11m for 0.1 s temporal resolution, and reaches V = 15^m in minute-long exposures. The system is equipped with a powerful computing facility and dedicated software pipeline allowing it to perform automatic detection, real-time classification, and investigation of transient events of different nature located both in the near- Earth space and at extragalactic distances. The objects routinely detected by MMT-9 include faint meteors and artificial Earth satellites.We discuss astronomical tasks that can be solved using MMT-9, and present the results of the first two years of its operation. In particular, we report the parameters of the optical flare detected on June 25, 2016, which accompanied the gamma-ray burst GRB160625B.     

The Concordia station on the Antarctic plateau: The best site on earth for the 21st century astronomers

On the Antarctic plateau, a joint project of French and Italian polar programmes is nearing completion: the Concordia station will be open for winter-over operation in 2005. The high altitude and high latitude of this site, the exceptionally cold, clear and stable atmosphere, its incredible astronomical seeing, the almost indefinitely flat snow surface and the not-so-difficult access make this site the most promising on Earth for future ground-based astronomical projects in various fields, including long term photometry, infrared high sensitivity imaging and high angular resolution and high contrast imaging.     

全天相机在多设备巡天中的应用

天文观测站夜天空星像星等信息和天区分布信息可用于指导多设备巡天观测.建立全天相机监测系统(Monitoring all-sky system)对本地天区夜天空实时监测,获取的监测图像需要有效的方法进行处理以提取全天图像星像信息.由于全天图像视场大和高阶扭曲的影响,采用天顶等距投影与多项式函数组合的方法计算图像的底片常数.天文定位的均方根残差约为0.15个像素.通过对图像中亮星部分测光得到的星等差,改正大气消光误差.最后使用HEALPix (Hierarchical Equal Area isoLatitude Pixelation)方法实现天区划分和每个天区可观测极限星等值的存储.     

丽江高美古的夜天光亮度

１９９６年１月～１９９８年３月,我们用光电方法测定了丽江高美古在Ｂ、Ｖ两个波段的夜天光亮度。为便于比较,在１９９６年１月还测定了云南天文台凤凰山台址的夜天光亮度。本文给出了观测结果,同时也列出了世界上一些天文台站的数据以供参考。