中国SONG项目节点全天云量监测方案

All Sky Cloud Coverage Monitoring for SONG-China Project

为实现中国SONG(Stellar Observations Network Group)项目在青海观测站云量信息的无人值守全自动监测,在国家天文台兴隆观测基地提供的全天相机基础上,对其硬件和软件做了相应的升级改造:将原来基于PC机的控制系统改为基于ARM(Advanced Reduced Instruction Set Computer Machine)单片机(MCU)的自动控制系统,提升了系统的可靠性;依据站点配属的夜天光监测仪,计算分析全天相机曝光参数与夜天光的数学关系,完成了曝光参数的自适应设置和图像采集;实现了采集图片的格式转换与数据库自动存储,达到了全天相机的无人值守全自动运行目标.

In order to monitor the cloud distributions at Qinghai station, a site selected for SONG（Stellar Observations Network Group）-China node, the design of the proto-type of all sky camera（ASC） applied in Xinglong station is adopted. Both hardware and software improvements have been made in order to be more precise and deliver quantitative measurements. The ARM（Advanced Reduced Instruction Set Computer Machine） MCU（Microcontroller Unit） instead of PC is used to control the upgraded version of ASC. A much higher reliability has been realized in the current scheme. Independent of the positions of the Sun and Moon, the weather conditions are constantly changing, therefore it is difficult to get proper exposure parameters using only the temporal information of the major light sources. A realistic exposure parameters for the ASC can actually be defined using a real-time sky brightness monitor that is also installed at the same site. The night sky brightness value is a very sensitive function of the cloud coverage, and can be accurately measured by the sky quality monitor. We study the correlation between the exposure parameter and night sky brightness value,and give the mathematical relation. The images of the all sky camera are inserted into database directly. All sky quality images are archived in FITS format which can be used for further analysis.