Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-24 Cooperative journals: 《天文研究与技术》
Abstract： The GCRF (Gaia Celestial Reference Frame) based on Gaia astrometric data has systematic differences from the ICRF (International Celestial Reference Frame) based on VLBI (Very Long Baseline Interferometry). An external independent evaluation of the data from Gaia is required to link optical and radio reference frame. Celestial bodies with both optical and radio radiation are generally used to link the two frames, quasars are used at the dark end (magnitude G≥15), and radio stars are used at the bright end (G≤13). It is very difficult to apply for the ordinary VLBI observations, so we try to focus on some geodesic observations that can use phase reference mode to observe radio stars in geodesic observations. In order to test the feasibility of this kind of observation, we use piggy-back phase referencing mode in geodetic observation of IVS (The International VLBI Service for Geodesy and Astrometry) and LBA (Large Baseline Array), and select Del Lib and HR 1099 as the targets. Our observations have obtained the VLBI images, flux densities and single￣epoch coordinates of these two radio stars, and the coordinate accuracy is higher than that of the previous work; at the same time, we also combine the data of the previous work to fit parallax and proper motion of the two radio stars. Our results are consistent with the results of the previous VLBI work and Gaia′s, and some of the accuracy is higher. Our work verify the feasibility of observing radio stars with piggy-back phase referencing mode in geodetic observation, and lay a certain foundation for the subsequent enrichment of VLBI astrometric samples of radio stars and linking of optical and radio reference frames.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-17 Cooperative journals: 《天文研究与技术》
Abstract： In order to complete the monitor of ultra-broadband spectrum for solar radio burst，Yunnan Observatories have designed and developed 4 solar radio spectrometers with the frequency range of 15-80 MHz，100-750 MHz，600-4 200 MHz and 4-15 GHz，which are called decametric, metric, decimetric and resolution centimetric solar radio spectrometer, respectively. For the decametric solar radio spectrometer, the spectral resolution and temporal resolution have reached 7. 6 kHz and 1 ms, respectively. For metric and decametric, the spectral resolution and temporal resolution have reached 9. 5 kHz and 10 ms, respectively. For the centimetric spectrometer, the spectral and temporal resolution have reached 76 kHz and 10 ms, respectively. Each spectrometer includes antenna system, receiver and digital spectrometer. In order to obtain a spectrum with ultra-high spectral resolution, the maximum word length of FFT is 262 144, which cannot be achieved by one-time FFT in FPGA, the parallel FFT algorithm is need. For the large word length of FFT, the data need to be transformed into a FFT with two small word length by doing a row decomposition and then parallel processing. In this paper, the algorithm is studied and simulated by using Matlab, then is applied to digital spectrometer. The test results of the digital spectrometer are good consistency with the simulation, indicating the successful application of the algorithm on the digital spectrometer. This paper introduces the composition of solar radio spectrometer and the method of implementing ultra-high resolution based on FPGA.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-23 Cooperative journals: 《天文研究与技术》
Abstract： Film thickness uniformity is an important indicator for the preparation of high-performance optical films. In order to further improve the uniformity of the film thickness of the 2.4 m primary mirror reflective film, an optimization scheme for the film thickness uniformity of the large-aperture telescope coating is designed. Based on the cosine distribution law followed by vacuum thermal evaporation, combined with the geometry of ZZ3200 vacuum coater and the actual needs of telescope coating, a film thickness calculation program is written to simulate the theoretical distribution of film thickness. The film thickness optimization design method and optimization results are given. Method 1: Add a correction mask at a suitable position inside the evaporation source, the results show that the radius of curvature of the mask is installed within 3 mm, and the Peak to Valley value of film thickness inhomogeneity decreases from 15% to 4% without mask, this method has certain universality, but the installation position of the mask should be accurately controlled; Method 2: Combined with the circular hole structure in the middle of the reflection primary mirror, the double ring evaporation source is designed, and the results show that when the center distance between the inner and outer ring evaporation sources is 10 cm and 130 cm, respectively, and the number of evaporation sources in the outer ring is 12 times that of the inner ring, the PV value of film thickness uniformity is 1.85%, which is designed for the mirror with a round hole in the center, and is suitable for most reflective astronomical telescope coatings.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-05-30 Cooperative journals: 《天文研究与技术》
Abstract：耀斑和日冕物质抛射（Coronal Mass Ejection，CME）期间产生的非热高能粒子流和激波是产生灾害性空间天气事件的两种主要因素，它们主要观测特征分别是具有快速频率漂移特征的射电Ⅲ型暴和具有较为缓慢频率漂移的射电Ⅱ型暴。本文主要介绍了使用概率霍夫变换(Probabilistic Hough Transform)的方法，在观测数据中自动识别出太阳射电Ⅲ型暴和Ⅱ型射电暴，并提取射电Ⅲ和Ⅱ型暴的特征参数，最后利用识别出的射电Ⅱ型暴的物理参数估计了CME激波的速度。
Subjects: Astronomy >> Astrophysical processes submitted time 2019-07-30 Cooperative journals: 《天文研究与技术》
Abstract：经过十余年的不断建设和发展，中国虚拟天文台（China-VO）已成为支撑天文学观测、研究、教学的重要技术和资源平台。随着多信使天文学和时域天文学时代的到来，虚拟天文台也需要升级自身的核心能力，以给天文工作者提供更精准的服务和技术支撑。为此，中国虚拟天文台团队结合天文学的发展方向和信息技术发展趋势梳理了一份核心技术需求清单，并以问卷的形式针对领域内专家和用户开展了调研。通过对调研结果的统计和分析，中国虚拟天文台明确了未来一段时期的主要努力方向和目标，计划采用平台化的开发模式，并开放第三方开发接口，以吸引更多感兴趣的开发者基于虚拟天文台资源做出实用的工具，更好地实现资源与技术向服务的快速转换。
Subjects: Astronomy >> Astrophysical processes submitted time 2019-05-30 Cooperative journals: 《天文研究与技术》
Abstract： 望远镜的观测日志在观测用户进行数据处理以及台站对观测数据进行存储、归档和发布的时候都非常重要，观测日志往往能提供很多观测信息以供用户判断观测数据的质量。在实际观测过程中，观测日志是通过观测助手或观测用户手工记录的，存在信息不全、笔误等多种可能，且纸质的日志也不利于后期观测数据的归档和发布。本文针对丽江2.4米望远镜YFOSC的观测数据，设计研发了一套自动记录观测日志的辅助系统，该系统可以自动记录观测数据的日志信息，并提供了修改错误信息的功能；系统中以观测用户的观测时间申请书编号为唯一代码对观测数据进行管理，从而实现了根据不同观测用户进行观测数据打包的功能。在保护观测数据权限的同时，降低了笔误带来的影响，提高了观测日志的准确性，最终提高观测效率。
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