## 1 Introduction
In recent years, an SIF network (FluoNet) consisting of several automated SIF systems based on the use of FluoSpec and FluoSpec 2 instruments has been established in the USA. FAME was recently designed using a specific QEpro with a spectral resolution of 730-786 nm and a spectral resolution of 0.15-0.17 nm [27]. One distinct innovation of FAME is the use of a datalogger as a control unit, allowing SIF and supporting environmental measurements to be precisely synchronized and easily integrated with existing data acquisition systems at eddy covariance (EC) tower sites [27]. However, all of the existing instruments mentioned above ignore the important functions of SIF at the red band. Another system, the fluorescence box (FLox) is installed in a portable tower and collects reflectance and SIF measurements at Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) site, which is covered by corn [28]. The FLox system consists of two spectrometers, including an Ocean Optics FLAME S (400-900 nm) and an Ocean Optics QEpro (650-800 nm), which has a FWHM of 0.3 nm. However, the effects of the atmosphere on SIF retrieval using tower-based measurements, especially for forest observations, are assumed to be negligible by currently used systems [29]. It is worth mentioning that the recent work has also addressed the importance of oxygen compensation on proximal sensing SIF retrieved at the O\({}_{2}\) band using Fraunhofer line discrimination (FLD) and spectral fitting methods (SFM) [29]. This method was used in the field measurements for a boreal forest ecosystem at a height of about 18 m to account for the energy reabsorption effects on SIF retrievals at the O\({}_{2}\)-A band [30]. In order to provide a reliable approach for collecting long-term SIF measurements in combination with continuous EC observations based on China's CO\({}_{2}\) flux observation network, ChinaSpec [31], an SIF observation network, was established in 2017 by several research groups, so far mainly from Chinese Academy of Sciences and Nanjing University. This network covers a variety of terrestrial ecosystems, including different types of agricultural, grassland, and forest ecosystems distributed across the mainland of China. This paper presents the details of the system components, instrument installation and calibration, as well as data collection and processing for the automated in situ SIF measurement (SIFSpec) system produced by Bergsun Inc. (Beijing, China) and used in the ChinaSpec network, along with two years of continuous SIF measurements on a maize crop at the Daman (DM) site. The objectives of this paper are as follows: (1) to present an overview of the composition and installation of the automated in situ SIF measurement system; (2) to introduce the data collection and processing procedure, especially for atmospheric correction; and (3) to test the performance of the SIFSpec system for SIF measurements and GPP estimation. The remaining parts of this paper are organized as follows. The details of the system components and data collection are provided in Section 2; descriptions of the site, instrument installation, and data processing are given in Section 3; long-term measurements and their links with crop GPP at the DM site are presented in Section 4; finally, the discussion and summary are presented as Sections 5 and 6, respectively.