# Sky Background Building of Multi-objective Fiber spectra Based on Mutual Information Network

## TL;DR

This paper introduces a novel sky background estimation model for multi-object fiber spectra that leverages mutual information and incremental training to improve sky background modeling, especially in the blue spectral region.

## Contribution

The proposed SMI model uses mutual information and incremental training to better estimate sky background by utilizing all fiber spectra, addressing environmental modeling limitations.

## Key findings

- SMI outperforms traditional methods in sky background estimation.
- The model effectively captures sky features in the blue spectral region.
- Experimental results on LAMOST spectra validate the method's accuracy.

## Abstract

Sky background subtraction is a critical step in Multi-objective Fiber spectra process. However, current subtraction relies mainly on sky fiber spectra to build Super Sky. These average spectra are lacking in the modeling of the environment surrounding the objects. To address this issue, a sky background estimation model: Sky background building based on Mutual Information (SMI) is proposed. SMI based on mutual information and incremental training approach. It utilizes spectra from all fibers in the plate to estimate the sky background. SMI contains two main networks, the first network applies a wavelength calibration module to extract sky features from spectra, and can effectively solve the feature shift problem according to the corresponding emission position. The second network employs an incremental training approach to maximize mutual information between representations of different spectra to capturing the common component. Then, it minimizes the mutual information between adjoining spectra representations to obtain individual components. This network yields an individual sky background at each location of the object. To verify the effectiveness of the method in this paper, we conducted experiments on the spectra of LAMOST. Results show that SMI can obtain a better object sky background during the observation, especially in the blue end.