Basic Survey Scheduling for the Wide Field Survey Telescope (WFST)

Abstract Aiming at improving the survey efficiency of the Wide Field Survey
Telescope (WFST), we have developed a basic scheduling strategy that takes into
account the telescope characteristics, observing conditions, and weather conditions
at the Lenghu site. The sky area is divided into rectangular regions, referred to as
‘tiles’, with a size of 2.577◦ × 2.634◦
slightly smaller than the focal area of the mosaic
CCDs. These tiles are continuously filled in annulars parallel to the equator. The
brightness of the sky background, which varies with the moon phase and distance
from the moon, plays a significant role in determining the accessible survey fields.
Approximately 50 connected tiles are grouped into one block for observation. To opti mize the survey schedule, we perform simulations by taking into account the length of
exposures, data readout, telescope slewing, and all relevant observing conditions. We
utilize the Greedy Algorithm for scheduling optimization. Additionally, we propose
a dedicated dithering pattern to cover the gaps between CCDs and the four corners
of the mosaic CCD array, which are located outside of the 3-degree field of view.
This dithering pattern helps to achieve relatively uniform exposure maps for the final
survey outputs.