# Five-year in-orbit background of Insight-HXMT

## TL;DR

This study analyzes five years of in-orbit background data from Insight-HXMT, detailing its evolution, characteristics, and the validity of background models for data analysis.

## Contribution

It provides a comprehensive analysis of the five-year background evolution of Insight-HXMT and assesses the accuracy of background models over time.

## Key findings

- Background characteristics are consistent with satellite design and space environment.
- The background model remains valid for recent observations.
- Systematic errors in background estimation are characterized annually.

## Abstract

Purpose: We present the five-year in-orbit background evolution of Insight-HXMT since the launch, as well as the effects of the background model in data analysis. Methods: The backgrounds of the three main payloads, i.e., Low-Energy Telescope, Medium-Energy Telescope and High-Energy Telescope, are described, respectively. The evolution of the background over time is obtained by simply comparing the background in every year during the in-orbit operation of Insight-HXMT. Results: The major observational characteristics of the Insight-HXMT in-orbit background are presented, including the light curve, spectrum, geographical distribution, and long-term evolution. The systematic error in background estimation is investigated for every year. Conclusion: The observational characteristics of the five-year in-orbit background are consistent with our knowledge of the satellite design and the space environment, and the background model is still valid for the latest observations of Insight-HXMT.