The Medium Energy X-ray Telescope (ME) is one of the main payloads of the Hard X-ray Modulation Telescope (dubbed as Insight-HXMT). The background of Insight-HXMT/ME is mainly caused by the environmental charged particles and the background intensity is modulated remarkably by the geomagnetic field, as well as the geographical location. At the same geographical location, the background spectral shape is stable but the intensity varies with the level of the environmental charged particles. In this paper, we develop a model to estimate the ME background based on the ME database that is established with the two-year blank sky observations of the high Galactic latitude. In this model, the entire geographical area covered by Insight-HXMT is divided into grids of $5\mathrm{°}\times 5\mathrm{°}$ in geographical coordinate system. For each grid, the background spectral shape can be obtained from the background database and the intensity can be corrected by the contemporary count rate of the blind FOV detectors. Thus the background spectrum can be obtained by accumulating the background of all the grids passed by Insight-HXMT during the effective observational time. The model test with the blank sky observations shows that the systematic error of the background estimation in $8.9-44.0$ keV is $\sim 1.3\text{\%}$ for a pointing observation with an average exposure ∼5.5 ks. We also find that the systematic error is anti-correlated with the exposure, which indicates the systematic error is partly contributed by the statistical error of count rate measured by the blind FOV detectors.

中能X射线望远镜（ME）是硬X射线调制望远镜（称为Insight-HXMT）的主要有效载荷之一。Insight-HXMT / ME的背景主要由环境带电粒子引起，并且背景强度受地磁场和地理位置的明显影响。在相同的地理位置，背景光谱形状稳定，但强度随环境带电粒子的水平而变化。在本文中，我们开发了一个基于ME数据库的模型来估算ME背景，该数据库是由高银河纬度的两年空白天空观测所建立的。在此模型中，Insight-HXMT覆盖的整个地理区域 分为 $5\mathrm{°}\times 5\mathrm{°}$在地理坐标系中。对于每个网格，可以从背景数据库中获得背景光谱形状，并且可以通过盲视场检测器的现代计数率来校正强度。因此，可以通过在有效观察时间内累计Insight-HXMT通过的所有栅格的背景来获得背景光谱。用空白天空观测值进行的模型试验表明，背景估计的系统误差较大。$8.9-44.0$ keV是 $〜1.3\text{％}$用于平均暴露〜5.5 ks的定点观察。我们还发现系统误差与曝光量呈反相关关系，这表明系统误差部分是由盲视场检测器测量的计数率的统计误差引起的。