Chinese Giant Solar Telescope Research Articles

Polarization Optical Design of 8-meter Chinese Giant Solar Telescope

Instrumental polarization is a vital factor for the accurate measurements of the solar magnetic field. It is necessary to optimize the optical design of the large solar telescope to obtain high accuracy solar magnetic field information. In this paper, an optimal design scheme based on four-mirror polarization compensation optics for the 8-meter giant solar telescope is presented. The polarization effect of pupil and field of view are analyzed by the polarization ray tracing programming, the telescope motion and wavelength properties of the field-effect are investigated detailedly. The result shows that, in the near infrared waveband which includes the magnetic sensitive spectral lines of He I 1.083 μm and Fe I 1.565 μm, the polarization-free field size is 0.91′, and the polarization-free field size in the visible band is 0.5′, in which the instrumental polarization of telescope is smaller than 2×10−4.

Active Alignment Modeling and Analysis of Chinese Giant Solar Telescope

Active Alignment Modeling and Analysis of Chinese Giant Solar Telescope

Chinese Giant Solar Telescope

Developing a next generation ground-based large solar telescope is the consensus of Chinese solar research community. Compared with the current one-meter-scale solar telescopes, next generation large solar telescopes are more focused on fundamental issues of solar physics and stellar physics. Therefore, the resolving power and measuring accuracy of magnetic field are required to be higher. The Chinese Giant Solar Telescope (CGST) is a reflecting telescope with a diameter of 8 m and a light-collecting area of not less than 20 m2. CGST is expected to detect the fundamental structures and the evolution of the solar atmosphere. It will provide detailed observational evidences for the final solution to fundamental physical problems such as the origin of stellar magnetic field and corona heating, providing the necessary theoretical and observational basis for accurate space weather prediction.

Progress of site survey for large solar telescopes in western China

AbstractExcellent sites are necessary for developing and installing ground-based large telescopes. For very-high-resolution solar observations, it had been unclear whether there exist good candidate sites in the west areas in China, including the Tibetan Plateau and the Pamirs Plateau. The project of solar site survey for the next-generation large solar telescopes, i.e., the Chinese Giant Solar Telescope (CGST) and the large coronagraph, has been launched since 2011. Based on the close collaboration among Chinese solar society and the scientists from NSO, HAO and other institutes, we have successfully developed the standard instruments for solar site survey and applied them to more than 50 different sites distributed in Xinjiang, Tibet, Qinghai, Sichuan, Yunnan and Ningxia provinces. We have built two long-term monitoring sites in Tibet and the large Shangri-La to take systematic site data. Clear evidence, including the key parameters of seeing factor, sky brightness and water vapor content, has indicated that a few potential sites in the large Tibetan areas should obtain the excellent astronomical conditions for our purpose to develop CGST and large coronagraph. We introduce the fresh site survey results in this report.

The preliminary analysis of sunshine durations with meteorological data for the Chinese Giant Solar Telescope site survey

Using meteorological data is fundamental in any site survey for astronomical instruments. As a first step, the analyses of sunshine duration for candidate sites are crucial for remote site survey for solar observing instruments. In western China, some ground-based meteorological stations have collected daily sunshine data from only partial-sky area since they had to be constructed in valley. One aim of this study is to demonstrate the geographical properties of those meteorological stations. Our goal is to investigate the true sunshine durations obtained if the stations are installed at the top of nearby mountain without screen effect. We make use of the three-dimensional geographical data from the Google Earth software and the statistical meteorological data from the National Meteorology Administration and the meteorological stations. All the 76 national basic meteorological observing stations with altitude over 3000 m located in western China are measured. Since astronomical instruments tend to be installed at the top of a mountain, we need to take into account the loss of the sunshine durations in making the remote site survey. Our results, after the compensation, show that the condition of sunshine duration in the Hengduan-Shan Mountains (HSM) area can meet the basic requirement of at least 2500 h yr(-1) for the Chinese Giant Solar Telescope (CGST) site survey.

Using a New Sky Brightness Monitor to Observe the Annular Solar Eclipse on 15 January 2010

For the future development of Chinese Giant Solar Telescope (CGST) in Western China, a new sky brightness monitor (SBM) has been produced for the site survey for CGST. To critically examine the performance and sensitivity of SBM, we used it in the observation of the annular solar eclipse in Dali City, Yunnan, on 15 January 2010. The observation met good weather condition with almost clear sky during the eclipse. The SBM measurement translates into the solar illuminance changes at a level of 2.4 \times 10-4I s-1 during the eclipse. The time of the minimal sky brightness in the field of view (FOV) is found consistent with the time of maximum eclipse. Two local sky regions in the FOV are chosen to make time series of calibrated skylight profiles. The evolution of the sky brightness thus calibrated also shows good consistency with the eclipse, particularly between the second and the third contacts. The minimal sky brightness in each local sky region took place within half a minute from the corresponding predicted contact time. Such small time delays were mainly caused by occasional cirri. The minimal sky brightness measured during the eclipse is a few millionths of I\odot with standard deviation of 0.11 millionths of I\odot. The observation supports that the singlescattering process (optically thin conditions) is the main contributor to the atmospheric scattering. We have demonstrated that many important aerosol optical parameters can be deduced from our data.We conclude that the new SBM is a sensitive sky photometer that can be used for our CGST and coronagraph site surveys.

Current Status and Future Programs for the Measurement of Solar Magnetic Field in China

In this presentation, we will summarize the progress in the observation and instrumentation for the measurement of solar magnetic field. And furthermore, some new Chinese projects in this aspect, such as the Space Solar Telescope, Chinese Giant Solar Telescope, etc., will be introduced too.