With the stable increase of carbon dioxide (CO_2) concentrations,space based measurement of CO_2 concentration in lower atmosphere by reflected sunlight in near infrared band has become a hot research topic.Recently,instruments sensitive to total CO_2 column data in near-surface have become available through the SCIAMACHY instrument on ENVISAT and TANSO-FTS on GOSAT.The developing hyper spectral CO_2 detector in China carried by TANSAT is going to be launched in 20 1 5.Hyper spectral CO_2 detector is designed to provide global measurements of CO_2 in lower troposphere,employing high resolution spectra of reflected sunlight taken simultaneously in near-infrared CO_2(1.6 1 mum and 2.06 mum) and O_2 (0.76 mum) bands. Associated with climate change and observation requirements of carbon sources and sinks,the feasibility of making CO_2 column concentration measurements with high-resolution and high-precision is studied by high resolution atmosphere radiation transfer model.In consideration of the application requirements, effects of key specifications of the hyper spectral CO_2 detector such as spectral resolution,sampling ratio and sign-to-noise ratio (SNR) on CO_2 detection are analyzed. Typical characteristics of hyper spectral CO_2 detector on TANSAT are grating spectrometer and arraybased detector.To achieve the column averaged atmospheric CO_2 dry air mole fraction (X_(CO_2)) precision requirements of 1 *10~(-6) -4*10~(-6),hyper spectral CO_2 detector should provide high resolution at first to resolve CO_2 absorption lines from continuous spectra of reflected sunlight.Compared to a variety of simulated spectral resolutions,the spectral resolution of hyper spectral CO_2 detector on TANSAT can resolve CO_2 spectral features and maintain the moderate radiance sensitivity.Since small size array detector-based instruments may suffer from undersampling of the spectra,influences of spectral undersampling to CO_2 absorption spectra are studied,indicating that sampling ratio should exceed 2 pixels/FWHM to ensure the accuracy of CO_2 spectrum. SNR is one of the most important parameters of hyper spectral CO_2 detectors to ensure the reliability. SNR requirements of CO_2 detector to different detection precisions are explored based on the radiance sensitivity factors.Results show that it is difficult to achieve SNR to detect 1 *10~(-6) -4*10~(-6) CO_2 concentration change in the boundary layer by solar shortwave infrared passive remote sensing,limited by the instrument development condition and level at present.However,the instrument SNR to detect 1 % change in the CO_2 column concentration is attainable.These results are not only conductive to universal applications and guides on developing grating spectrometer,but also helpful to better understand the complexity of CO_2 retrieval.