Carbon Observing Satellite (Tan-Sat) is the first satellite of China designed to monitor column-averaged atmospheric carbon dioxide () by detecting gas absorption spectra of the solar shortwave infrared radiation reflected from the Earth’s surface and atmosphere. Two instruments are accommodated on Tan-Sat: the high resolution hyperspectral sensor for carbon observation grating spectrometer (HRHS-GS) and the cloud and aerosol polarimetric imager (CAPI). HRHS-GS will provide the space-based measurements of on a scale and with the accuracy and precision to quantify terrestrial sources and sinks of . CAPI is used to identify the contamination by optically thick clouds and to minimize the impact of scattering by aerosol. These two instruments work together to collect global column concentrations with correction for cloud and aerosol contamination. The instrument design of HRHS-GS is presented. Ocean reflectivity and the incident radiation of the instrument for transverse electric and transverse magnetic polarizations in glint mode are discussed. The changes to glint mode operation are described. The spectral characteristics of HRHS-GS were determined through the laser-based spectral calibration. The onboard spectral calibration method based on spectrum matching is introduced. The availability was verified, satisfying the onboard spectral calibration accuracy requirement of better than ( is spectral resolution).