Data Processing Pipeline for Pointing Observations of Lunar-based Ultraviolet Telescope

TL;DR

This paper details a specialized data processing pipeline for the Lunar-based Ultraviolet Telescope, enabling accurate photometry of variable objects in the near-ultraviolet spectrum despite lunar daytime operational constraints.

Contribution

The paper introduces a novel data processing pipeline tailored for LUT's unique lunar daytime environment, including strategies for stray light removal and flat fielding.

Findings

Photometric accuracy of ~0.02 mag for 10 mag stars

Pipeline effectively processes LUT data with smooth operation

Detection limit of 13.5 mag at 5σ

Abstract

We describe the data processing pipeline developed to reduce the pointing observation data of Lunar-based Ultraviolet Telescope (LUT), which belongs to the Chang'e-3 mission of the Chinese Lunar Exploration Program. The pointing observation program of LUT is dedicated to monitor variable objects in a near-ultraviolet (245-345 nm) band. LUT works in lunar daytime for sufficient power supply, so some special data processing strategies have been developed for the pipeline. The procedures of the pipeline include stray light removing, astrometry, flat fielding employing superflat technique, source extraction and cosmic rays rejection, aperture and PSF photometry, aperture correction, and catalogues archiving, etc. It has been intensively tested and works smoothly with observation data. The photometric accuracy is typically ~0.02 mag for LUT 10 mag stars (30 s exposure), with errors come from background noises, residuals of stray light removing, and flat fielding related errors. The accuracy degrades to be ~0.2 mag for stars of 13.5 mag which is the 5{\sigma} detection limit of LUT.