Subjects: Astronomy >> Astrophysical processes submitted time 2022-11-17 Cooperative journals: 《天文研究与技术》
Abstract： Shadowing effects is one of the main consideration factors in designing complex system with multiple antennas. There will be 373 sets of antennas in Mingantu Station, after completing the construction of the program Meridian II equipment of National Major Science and Technology Infrastructure. Limited by test site, model complexity and computation, shadowing effect is usually hard to measure and to predict especially for electrically large-size structures. The observed solar radio data on S/C/X bands between 2017 and 2020 by MST (Mingantu Solar Radio Telescope), present the shadowing effect with the 20m antenna and remote hills as obstacles. The observed data with shadowing effect can be divided into antenna area, atmosphere area and hills area with different shadowing characteristics. Based on the prediction method of single knife-edge diffraction loss recommended by ITU-R P.526-15, a model of 20m antenna reflector is built, the shadowing effects on S/C/X-bands are simulated, and the results show agreement with those of observation. From simulation and observing results, shadowing effects are related with wavelength, obstacle character, distance and angle among obstacle, source and receiving antenna, the receiving antenna’s beam, and dynamic range of receiving system, etc.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2018-06-22 Cooperative journals: 《天文研究与技术》
Abstract： It is an important method of space weather predictor to monitor the solar flux continuously in long-term with the ground-based solar radio telescopes. Solar flux is one of the most useful observable indexes for predicting kinds of turbulence occurred on the earth excited by the sun activities and solar ultraviolet radiation. It represents the solar total activity level, especially the 10.7cm solar flux, which has long been used as solar activity index since 1960s. With the financial support of NSMC (National Satellite Meteorological Center) and NAOC (National Astronomical Observatories), two new 3-bands radio telescopes used to monitor the solar flux on three wavelengths（10.7cm, 6.6cm and 3.3cm）have been set up in 2016 December in Mingantu Observatory of NAOC in inner Mongolia province and in Tashkurghan in Xinjiang province. The two telescopes, named MST and TST separately, each consisting of a 3-m size diameter parabolic antenna, 2-10 GHz wide band two-polarization feed, a constant temperature front-end box, will give more time coverage to observe the sun with the distance between the two sites is about 5000km and 2.67 hours zone away. Constant temperature of the front-box helps to keep the system stability, especially in Mingantu and Tashkurghan the weather changes severely from hour to hour. After calibrated, data sets of fits format will be uploaded automatically everyday through the internet to the data reduction center of NSMC, used as space weather monitoring data. Double noise sources methods is first adopted in system calibration.The system stability is better than 1% in over 10 hours, system sensitivity is better than 1 s.f.u., with Δf=10MHz and Δt=0.1s. The electromagnetic environment of MAT is much better than that of TST. In 2017, MST has gotten some preliminary results. In 2018, more efficient data can be expected, and further work will be done in system calibration and system stability testing and analyzing.
Subjects: Astronomy >> Astrophysical processes submitted time 2017-10-20 Cooperative journals: 《天文研究与技术》
Abstract：叙述了国家天文台升级改造后的2 840 MHz太阳射电辐射流量计的设计特点、性能、结构及观测结果。升级改造后的太阳射电辐射流量计将在较高时间分辨率上实时得到2 840 MHz频率上的太阳流量，为太阳物理研究积累丰富的观测数据，是太阳活动监测和预报的重要参数之一
Subjects: Astronomy >> Astrophysical processes submitted time 2017-10-11 Cooperative journals: 《天文研究与技术》
Abstract：明安图射电频谱日像仪(Mingantu Ultrawide SpEctral Radioheliograph, MUSER)是新一代具有高时间、高空间、高频率分辨率的太阳专用射电望远镜，采用综合孔径原理成像，所以幅度和相位是决定最后成图质量的关键因素。天线的相位方向图会影响日像仪输出的幅度和相位，根据日像仪的馈源设计和综合孔径原理，针对明安图射电频谱日像仪天线数目多，且为户外环境，根据天文观测须经常测试天线性能的特点，给出了基于相关结果测量日像仪天线相位方向图的方法，该方法可以直接通过日像仪的相关输出结果高效准确地得到天线的相位方向图。对MUSER-I天线的相位方向图进行了测量和分析，同时分析了天线相位方向图对日像仪成像的影响，为得到高质量的太阳图像提供了参考和保障。
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