The Software Design And Implementation Of Multi-Channel High-Resolution Imaging System In NVST

The New Vacuum Solar Telescope is a 1-meter, ground-based telescope that offers unparalleled performance to solar observations. One of the important instruments in NVST is multi-channel high-resolution imaging system, which consists of five main work wavelength, including Hα, TiO-band, G-band, Ca II(8542?) and He I(10830?). Up to now, Hα and TiO-band channels are being used.The Hα channel is narrow-band imaging system, equipped with a tunable Lyot filter. For the interpretation of narrow-band filtergrams is difficult due to the crosstalk between brightness and Doppler shift modulation, the observation system is required to perform multi-offband observation in Hα channel to obtain a scanned profile in order to get meaningful physical information. TiO-band is broad-band imaging system and uses a high-cadence CMOS. To achieve much higher cadence for some specific observation, it shall support to decrease the FOV to increase the acquisition speed of camera. While the software provided by camera manufactures failed to meet the observation need, an new observational software system is constructed to satisfy the different observational need of two channels.Taking the factors into account that another three channel will soon be added and high-cadence cameras will come into uses, the software architecture designed for NVST acquisition system should provide scalability and flexibility to adapt to changes in technologies throughout the lifetime of NVST. To achieve this goal, distributed multi-terminal deployment and a loosely coupled system is adopted. The system is based on a tiered software architecture implemented as three primary system, Observation Control System(OCS), Instrument Control System(ICS) and Data Handling System(DHS). OCS interacts with stuff and coordinates the overall observation operations. ICS manages the instruments and DHS manages the data operation of saving, processing and transfer. To decouple the logical systems so that they can be developed independently, the software architecture is separated into functional architecture and technical architecture, patterned after a similar approach adopted by ACS(ALMA Common Service). The technical architecture describes the underlying implementation of technical aspect, such as threading and message broadcasting. The functional architecture, in contrast to technical architecture, describes the functional behavior. So the container/component mode is adopted to achieve this separation of architecture. The container manages many components which provide functional behavior.This paper describes the deployment of acquisition system and the design of software architecture on top of container/component mode to achieve the scalability and flexibility to adapt the changes in observational instruments and in observation methods.