Colour equations for UK Schmidt Telescope Tech-Pan film exposures

Kodak Technical Pan (Tech-Pan) film is a standard panchromatic emulsion that was used at the UK 1.2-m Schmidt Telescope (UKST) for a variety of broad-band exposures between 1992 and 2003. However, despite its versatility and frequent use, no formal presentation of its colour-term stability has been provided. A sample of 32 short-exposure Tech-Pan films was specifically acquired in five wavebands with a view to establishing the photometric relationships between Tech-Pan and the equivalent glass-based emulsions previously used. These films have been measured using the SuperCOSMOS measuring machine and the data reduced to provide the appropriate quantitative information. New colour terms relating these measurements to the Cousins photoelectric system are presented. They are shown to be stable, reproducible, generally small and similar to colour terms previously derived for the older emulsions on glass that Tech-Pan effectively replaced. These results give confidence in the use of Tech-Pan photometry from on-line UKST legacy survey archives.     

Multi-component study of extended sources with a likelihood method

The spectral and morphological analysis for gamma-ray sources with multiple emission components remains a major challenge for Cherenkov telescopes due to background emission from diffuse gamma rays. Current methods of background suppression, usually based on the bin-by-bin subtraction of OFF-source data do not allow an analysis of the various background components. As an alternative, we present an approach based on an event-by-event likelihood fit of ON-source data, using a combined spectral model for the source emission as well as for the gamma-like background obtained from fits of the OFF-source data. Multiple emission components are separated by successive fits in different energy regimes and spectral variations inside the extended source is derived. The performance of this approach is evaluated with toy Monte-Carlo studies. For the application to real data, two well-studied H.E.S.S. sources are re-examined: the extragalactic point-source PKS 2155-304 and the extended pulsar wind nebula HESS J1825-137. For the latter, radial variation of the emission spectral index was evaluated, confirming earlier findings by the H.E.S.S. collaboration.     

Bayesian approach for counting experiment statistics applied to a neutrino point source analysis

In this paper we present a model independent analysis method following Bayesian statistics to analyse data from a generic counting experiment and apply it to the search for neutrinos from point sources. We discuss a test statistic defined following a Bayesian framework that will be used in the search for a signal. In case no signal is found, we derive an upper limit without the introduction of approximations. The Bayesian approach allows us to obtain the full probability density function for both the background and the signal rate. As such, we have direct access to any signal upper limit. The upper limit derivation directly compares with a frequentist approach and is robust in the case of low-counting observations. Furthermore, it allows also to account for previous upper limits obtained by other analyses via the concept of prior information without the need of the ad hoc application of trial factors. To investigate the validity of the presented Bayesian approach, we have applied this method to the public IceCube 40-string configuration data for 10 nearby blazars and we have obtained a flux upper limit, which is in agreement with the upper limits determined via a frequentist approach. Furthermore, the upper limit obtained compares well with the previously published result of IceCube, using the same data set.     

LAMOST反射施密特改正镜新型镜罩设计

针对LAMOST反射施密特改正镜的特殊防护及功能要求,经多种方案设计和实验,最终设计和制造了一套新型轻质帘式镜罩系统,并得到了成功应用。首先回顾LAMOST反射施密特改正镜镜罩的功能要求,以及镜罩的样机实验和方案遴选;详细介绍最终选定的新型轻质帘式镜罩系统的具体机械结构、电气控制方法以及现场安装调试等研究设计工作。该新型镜罩主体功能件为轻型布帘罩体,两侧各通过一组滑块联接于两根平行的弯曲C形轨道,并由2组4只电机通过拉线的方式实现电动开闭;为允许反射施密特改正镜可转至竖直位置,轨道的末端采用电动推拉实现弯折,以避免结构干涉。该镜罩已在LAMOST望远镜上投入正常运行,安全性得到了考验和确认。     

Size matters

The new generation of ground‐based, large‐aperture solar telescopes promises to significantly increase our capabilities to understand the many basic phenomena taking place in the Sun at all atmospheric layers and how they relate to each other. A (non‐exhaustive) summary of the main scientific arguments to pursue these impressive technological goals is presented. We illustrate how imaging, polarimetry, and spectroscopy can benefit from the new telescopes and how several wavelength bands should be observed to study the atmospheric coupling from the upper convection zone all the way to the corona. The particular science case of sunspot penumbrae is barely discussed as a specific example (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

GREGOR solar telescope: Design and status

The integration and verification phase of the GREGOR telescope reached an important milestone with the installation of the interim 1 m SolarLite primary mirror. This was the first time that the entire light path had seen sunlight. Since then extensive testing of the telescope and its subsystems has been carried out. The integration and verification phase will culminate with the delivery and installation of the final 1.5 m Zerodur primary mirror in the summer of 2010. Observatory level tests and science verification will commence in the second half of 2010 and in 2011. This phase includes testing of the main optics, adaptive optics, cooling and pointing systems. In addition, assuming the viewpoint of a typical user, various observational modes of the GREGOR Fabry‐Pérot Interferometer (GFPI), the Grating Infrared Spectrograph (GRIS), and high‐speed camera systems will be tested to evaluate if they match the expectations and science requirements. This ensures that GREGOR will provide high‐quality observations with its combination of (multi‐conjugate) adaptive optics and advanced post‐focus instruments. Routine observations are expected for 2012 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

基于自回归滑动平均模型的大口径天线风速预测方法

针对大口径、高性能射电望远镜天线受到的随机及时变风扰的问题, 利用自回归滑动平均模型预测望远镜周围风速, 提前计算风致结构变形量, 同时为望远镜伺服控制系统提供足够执行时间来降低风扰影响. 基于新疆奇台110m口径全向可动射电望远镜(QiTai Telescope, QTT)台址风场数据特征, 通过赤池信息准则和贝叶斯信息准则辨识模型阶次, 利用最大似然法估计模型参数, 分析模型残差特性以检验自回归滑动平均模型的有效性. 通过计算不同季度预测数据与测试数据偏差得到预测模型的精度, 夏季平均绝对误差为0.133mcdots^-1, 秋季平均绝对误差为0.162mcdots^-1, 冬季平均绝对误差为0.287mcdots^-1. 整体来看, 基于QTT台址不同季度风速数据建立的自回归滑动平均模型预测误差较小, 满足射电望远镜风扰控制系统的需求, 能为大口径射电望远镜风扰控制提供必要数据支撑.     

基于粒子群优化的LAMOST初始波长定标方法

大天区面积多目标光纤光谱天文望远镜(Large Sky Area Multi-Object Fiber Spectroscopic Telescope,LAMOST)初始波长定标操作,对于在先验定标系数附近搜索解空间内的每一点,通过插值法生成对应定标系数下的虚拟定标灯谱,再将生成的虚拟定标灯谱与实测定标灯谱作互相关运算,使得相关系数最大时对应的定标系数即为初始定标结果,其实质是一个多参数寻优问题.粒子群优化是一种基于群体智能的随机全局优化算法,具有实现简单、精度高、收敛快的特点.鉴于粒子群优化的优异性能,提出一种基于粒子群优化的LAMOST初始波长定标方法,并设计相应算法和测试实验.实验结果表明,基于粒子群优化的LAMOST初始波长定标在收敛性、解的质量、运行时间等方面都优于基于改进遗传算法参数寻优方法.     

LAMOST低分辨率光谱仪体位相全息光栅的参数测量

对LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) 16台低分辨率光谱仪共34块体位相全息光栅(VPHG)的参数进行了系统测试,给出了测试方法和测量结果,测量参数包括光栅的刻线密度、闪耀角、衍射效率曲线以及闪耀角偏差对衍射效率的影响等,测量的数据为LAMOST光谱仪的安装提供了依据.     

The new IRSOL solar telescope control system

We would like to present a new control system for the solar telescope now in operation at the Swiss institute, Istituto Ricerche Solari Locarno (IRSOL). The control software is multi‐client capable, and optionally uses the primary image of the sun projected on a position sensor or the axis encoder for guiding. The hardware and software consist of three completely separate levels, which communicate with each other via ASCII commands. We shall describe the general principles implemented in the course of the development. We consider it important that this text is also applicable to other astronomical device controls. Therefore we explain our specific solution next to general principles (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)