Blind search for 21-cm absorption systems using a new generation of Chinese radio telescopes

Neutral hydrogen clouds are known to exist in the Universe, however their spatial distributions and physical properties are poorly understood. Such missing information can be studied by the new generation of Chinese radio telescopes through a blind search of 21-cm absorption systems. We forecast the capabilities of surveys of 21-cm absorption systems by two representative radio telescopes in China - the Five-hundred-meter Aperture Spherical radio Telescope （FAST） and Tianlai 21-cm cosmology experiment （Tianlai）. Facilitated by either the high sensitivity （FAST） or wide field of view （Tianlai） of these telescopes, more than a thousand 21-cm absorption systems can be discovered in a few years, representing orders of magnitude improvement over the cumulative discoveries in the past half a century.

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, also called the Guo Shou Jing Telescope) is a special reflecting Schmidt telescope. LAMOST’s special design allows both a large aperture (effective aperture of 3.6 m–4.9 m) and a wide field of view (FOV) (5°). It has an innovative active reflecting Schmidt configuration which continuously changes the mirror’s surface that adjusts during the observation process and combines thin deformable mirror active optics with segmented active optics. Its primary mirror (6.67m×6.05 m) and active Schmidt mirror (5.74m×4.40 m) are both segmented, and composed of 37 and 24 hexagonal sub-mirrors respectively. By using a parallel controllable fiber positioning technique, the focal surface of 1.75 m in diameter can accommodate 4000 optical fibers. Also, LAMOST has 16 spectrographs with 32 CCD cameras. LAMOST will be the telescope with the highest rate of spectral acquisition. As a national large scientific project, the LAMOST project was formally proposed in 1996, and approved by the Chinese government in 1997. The construction started in 2001, was completed in 2008 and passed the official acceptance in June 2009. The LAMOST pilot survey was started in October 2011 and the spectroscopic survey will launch in September 2012. Up to now, LAMOST has released more than 480 000 spectra of objects. LAMOST will make an important contribution to the study of the large-scale structure of the Universe, structure and evolution of the Galaxy, and cross-identification of multiwaveband properties in celestial objects.

The photometric system of the One-meter Telescope at Weihai Observatory of Shandong University

The one-meter telescope at Weihai Observatory （WHO） of Shandong University is an f/8 Cassegrain telescope. Three sets of filters are installed in a dual layer filterwheel that use Johnson-Cousins UBVRI, Sloan Digital Sky Survey u′g′r′i′z′ and Stomgren uvby. The photometric system and the CCD camera are introduced, followed by detailed analysis of their performances, and determination of the relevant parameters, including gain, readout noise, dark current and linearity of the CCD cam- era. In addition, the parameters describing the site＇s astro-climate, including typical seeing, statistics on the number of clear nights and average sky brightness, based on data gathered from Sep. 2007 to Aug. 2013, are systematically studied and reported in this work. Photometric calibrations were done using Landolt standard star obser- vations spanning eight nights, which yielded transformation coefficients, photometric precision and system throughput. The limiting magnitudes are simulated using the derived calibration parameters and classic observation conditions at WHO.

The site conditions of the Guo Shou Jing Telescope

The weather at the Xinglong Observing Station, where the Guo Shou Jing Telescope （GSJT） is located, is strongly affected by the monsoon climate in north- east China. The LAMOST survey strategy is constrained by these weather patterns. We present statistics on observing hours from 2004 to 2007, and the sky brightness, seeing, and sky transparency from 1995 to 2011 at the site. We investigate effects of the site conditions on the survey plan. Operable hours each month show a strong cor- relation with season： on average there are eight operable hours per night available in December, but only one-two hours in July and August. The seeing and the sky trans- parency also vary with season. Although the seeing is worse in windy winters, and the atmospheric extinction is worse in the spring and summer, the site is adequate for the proposed scientific program of the LAMOST survey. With a Monte Carlo simulation using historical data on the site condition, we find that the available observation hours constrain the survey footprint from 22h to 16h in right ascension; the sky brightness allows LAMOST to obtain a limiting magnitude of V = 19.5 mag with S/N= 10.

气象观测场在汽车试验场中的应用研究

汽车试验场作为汽车开展道路测试的重要场所,用于验证汽车产品的品质以及可靠性。除了场地道路外,气象条件作为汽车道路测试的重要一环,在《GB/T12534-1990汽车道路试验方法通则》中也有明确要求,如:试验时应是无雨无雾天气,相对湿度小于95%,气温0-40℃,风速不大于3m/s。同时气象条件也作为试验场道路管控的重要依据,实时风速、雨量、能见度等信息为场地管理者发布限速、限行、封场等通知提供必要参考依据,直接影响道路测试安全管控的及时性。因此,文章从气象观测场的建设、气象服务、异常天气道路管控等方面开展气象观测场在汽车试验场中的应用研究。

Characteristics and Performance of the CCD Photometric System at Lulin Observatory

The Lulin One-meter Telescope at Lulin Observatory in Taiwan started open-use observations in January 2003. In order to evaluate the performance of the CCD photometric system, the characteristics and quality of the site, we obtained data of photometric standards as well as calibration data from February to November 2004. We report here the results of our analysis including the gain, readout noise, dark current and linearity of the CCD camera, and transformation coefficients, total throughputs, night sky brightnesses and limiting magnitudes for UBVRI bands.

Spatial Model of Sky Brightness Magnitude in Langkawi Island, Malaysia

Sky brightness is an essential topic in the field of astronomy, especially for optical astronom- ical observations that need very clear and dark sky conditions. This study presents the spatial model of sky brightness magnitude in Langkawi Island, Malaysia. Two types of Sky Quality Meter （SQM） manu- factured by Unihedron are used to measure the sky brightness on a moonless night （or when the Moon is below the horizon）, when the sky is cloudless and the locations are at least 100 m from the nearest light source. The selected locations are marked by their GPS coordinates. The sky brightness data obtained in this study were interpolated and analyzed using a Geographic Information System （GIS）, thus producing a spatial model of sky brightness that clearly shows the dark and bright sky areas in Langkawi Island. Surprisingly, our results show the existence of a few dark sites nearby areas of high human activity. The sky brightness of 21.45 mag arcsec-2 in the Johnson-Cousins V-band, as the average of sky brightness equivalent to 2.8 × 10-4cd m-2 over the entire island, is an indication that the island is, overall, still relatively dark. However, the amount of development taking place might reduce the number in the near future as the island is famous as a holiday destination.