Data quality control system and long-term performance monitor of the LHAASO-KM2A

TL;DR

This paper presents a comprehensive data quality control system for the LHAASO-KM2A observatory, ensuring long-term stability and reliable cosmic ray and gamma-ray data collection through a three-level monitoring approach.

Contribution

It introduces a novel three-level quality control system for LHAASO-KM2A, enhancing data reliability and stability over a multi-year observation period.

Findings

Stable pointing and angular resolution over two years.

Consistent results from Moon shadow and Crab Nebula observations.

Estimated pointing errors within a few millidegrees.

Abstract

The KM2A is the largest sub-array of the Large High Altitude Air Shower Observatory (LHAASO). It consists of 5216 electromagnetic particle detectors (EDs) and 1188 muon detectors (MDs). The data recorded by the EDs and MDs are used to reconstruct primary information of cosmic ray and gamma-ray showers. This information is used for physical analysis in gamma-ray astronomy and cosmic ray physics. To ensure the reliability of the LHAASO-KM2A data, a three-level quality control system has been established. It is used to monitor the status of detector units, stability of reconstructed parameters and the performance of the array based on observations of the Crab Nebula and Moon shadow. This paper will introduce the control system and its application on the LHAASO-KM2A data collected from August 2021 to July 2023. During this period, the pointing and angular resolution of the array were stable. From the observations of the Moon shadow and Crab Nebula, the results achieved using the two methods are consistent with each other. According to the observation of the Crab Nebula at energies from 25 TeV to 100 TeV, the time averaged pointing errors are estimated to be $-0.003^{\circ} \pm 0.005^{\circ}$ and $0.001^{\circ} \pm 0.006^{\circ}$ in the R.A. and Dec directions, respectively.