Spectral Efficiency Testing and Error Analysis of Space Slitless Spectrograph

The slitless spectroscopy assembly of the China Space Survey Telescope (CSST) will be installed in front of the main focal plane detectorof the sky survey module to conduct wide-field, wide-band slitless spectral observations. As an important dispersion element of the sky survey module, the slitless spectroscopy assembly is composed of 24 gratings and 12 filters. Spectral efficiency is one of the key technical parameters of the slitless spectroscopy assembly, and it needs to be tested during the development process. Due to the large envelope of the slitless spectroscopy assembly, commercial spectral efficiency measurement equipment cannot be used for testing. This paper addresses the issue of spectral efficiency testing for the slitless spectroscopy assembly. Firstly, the basic structure and measurement principles of the slitless spectroscopy assembly spectral efficiency test platform built in the laboratory are introduced. Then, the steps and results of the spectral efficiency measurement for the qualification model of the slitless spectroscopy assembly are given. Finally, the accuracy of the measurement results is analyzed and calculated using error synthesis theory. The measurement and calculation results show that the average spectral efficiency of the qualification model for the slitless spectroscopy assembly is respectively 51.9% in the GU band, 67.9% in the GV band, and 71.6% in the GI band (67.7% in the 900 nm–1000 nm band), meeting the technical requirements.