The Design and Implementation of Spectropolarimetric Observation Mode at 1-Meter New Vacuum Solar Telescope

As one of the observation terminals of the 1-meter New Vacuum Solar Telescope (NVST) at Fuxian-Lake, the multi-band spectrometer is required to have two observation modes, ie, spatial 2D scanning observation and spectropolarimetric measurement, as to achieve diagnosis of solar vector magnetic field and its dynamic characteristics. The work of this paper is closely related to how to structure and realize the above two observation modes. Firstly, the basic requirements in observation modes of the three important photoelectric mechanisms (spatial scanning mechanism, polarization analyzer, and instrument polarization calibration mechanism) are made clear. Second, from practical solar physics requirements, the specific implementation methods of these requirements (continuous or step-by-step), control accuracy (10^-2 or 10^-3), and signal-to-noise ratio improvement method (multi-frame superposition or multi-group superposition), are analyzed. Finally, flow charts of various observation modes are summarized, and different observation modes are integrated into one sampling control program which is put into practical measurement. Multiple groups of 2-D spatial scanning observations and sunspot spectropolarimetric measurement are carried out with good results achieved.