First Near-infrared Sky Brightness Measuring Meter Established in Ali Observatory, Tibet, and Gave Birth To Its First Set of Data

  • [2017-11-04]
    The near-infrared sky brightness measuring meter was established successfully in Ali, Tibet that covers the infrared band, introduced with the joint efforts of the National Key Laboratory of Nuclear Detection and Nuclear Electronics of the Department of Modern Physics and the Department of Astronomy of University of Science and Technology of China, as well as the Polar research Institute of China. It has measured the sky brightness at a near-infrared wavelength of JHKs round the observatory in summer, which is also the first set of data of the observatory. The rate of flow of J waveband is about 900μJyarcsec-2, with that of H waveband 2000μJyarcsec-2 and that of Ks 1000μJyarcsec-2. Data reveals that the intensity of near-infrared sky brightness in Ali appears subtle at fine summer night, and ensures the stability of the instrument and the capability to observe in a long run. This is a good news for the coming observation in winter. In late August, Member of the Political Bureau of CPC Central Committee and Vice Premier LIU Yandong investigated in Tibet and inspected Ali observatory and its new member- the near-infrared sky brightness measuring meter.

     

    Ali Observatory in the near infrared band J, H, Ks band sky background data. 

    While the best world-class observation stations settle on the top of Mauna Kea in Hawaii, Andes in Chile and Canary island in Atlantic, Asia, however, was never home to any of those in the past. Yet things have changed since astronomers from East Asia Central Observatory Alliance(EACOA) consisting of mainland China, Japan , Korea and Taiwan made Tibet the candidate to house a world-class observatory in East Asia. Known as the Third Pole after the North and South Pole, Tibet scores high for its daylight abundance, good transparency, low moisture and decent astronomical seeing. As a result, Ali, located in Tibet high with an altitude of 5100m breeds perfect infrared and submillimetre observation. To the best of our knowledge, Ali observatory has as decent a seeing as Mauna Kea observatory, which exceeds 0.8 second of arc.

    Ali Observatory, Tibet installation site

    In recent years, China has laid vast emphasis on developing astronomy concerning about infrared band and imaging systems, and aims to launch a third survey telescope AST-3 at Antarctic Kunlun Station that deals with infrared band, while the Kunlun Dark Universe Survey Telescope(KDUST) covers wavelengths between 0.4μm-2.5μm with the infrared band included. Meantime, a 12m-caliber optical infrared telescope on the list of great national construction of science and technology infrastructure in the 13th Five-Year Plan, chose its first site in Ali, Tibet. But data of the infrared sky brightness in this area was yet to be acquired. In general, the radiation intensity of the infrared sky brightness affects the major performance of infrared telescopes and other measuring instruments to a large degree, for instance, the depth of the sky survey, the furthest star observed and the exposure time of the imaging system, Whether a location is suitable for the construction of astronomical instruments or not, depends a lot on local average radiation intensity of infrared sky brightness and the variable parameters.

    Official parade

    Beware of the value in such measuring, the team led by Associate Prof. WANG Jian from the National Key Laboratory of Nuclear Detection and Nuclear Electronics of the Department of Modern Physics and another Associate Prof. ZHU Qingfeng from the Department of Astronomy, USTC, have already begun their research on the near-infrared sky brightness at Ali observatory and Antarctic Kunlun Station. Like Kunlun Station with a high altitude, Ali observatory exhibits excellent conditions for astronomical observation as well and may provide a perfect domestic operation testing environment for astronomical instruments at kunlun Station. The design of the research exactly targets at those extreme conditions we may encounter in Antarctica, like excessively low temperature, high altitude, low pressure(e.g. The average temperature collapses to -60℃ with a minimum of -80℃ at polar night, with the altitude of 4087m and the atmospheric pressure of 0.5atm at Kunlun Station.),shortage of electricity and so on, and adjusts the optical performance, automatic observation, low-noise-reading electronics, structure and electronic control of the measuring meter. So far, the measuring meter has been installed and put into operation. Following the first near-infrared sky brightness data at Ali observatory will be that of winter observation. Hopefully this will be a solid foundation for further research at Antarctic Kunlun Station.

     (WEI Lianyi, USTC News Center,Image by National Key Laboratory of Nuclear Electronics)

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