Design of the Distributed Real-Time Control and Image-Acquisiton Software System for the YNAO 1m Solar Telescope

The 1m infrared solar tower is located at the Fuxian Solar Physics Observing Station, Yunnan Porvince. It is about 60 kilometers southeast of Kunming, the captal of the Yunnan Province, China. It will serve as a major ground-based optical and near-infrared solar observation equipment for China throughout the first few decades of this century, and is currently the world's largest vacuum solar telescope. This paper focuses on the design of its multiple-CCD real-time control and image-acquisition software system. The software system adopts an overall architecture of master-to-front. In order to solve the problem of communication between the main-control and front-end systems, four kinds of application-layer communication protocols are designed: basic system initializing protocols, controlling protocols, status protocols, and parameter-setting protocols. In order to obtain a data processing speed matching the CCD recording speed, we use double-buffers and double-ADCs to receive the data from CCD, and use the DMA technology to directly transfer data from the storages of CCD to the memories of the front-end computer. The Socket, data-acquisition, and data-processing threads are designed for the front-end system and the main-control system to realize the synchronization for multi-CCD image acquisition. The front-end system sends "heart-beat" information every 10 seconds to the main-control system to confirm it is active. Currently, the optical, mechanical, and electrical components of the solar tower have been completely installed. The Gigabit Ethernet, computers, and CCDs have also been installed. The software system described in this paper has been deployed and early-stage runnings show that it can serve the routine operations of the solar tower.