Abstract: The increasing resolution of LEO（low earth orbit） remote sensing satellite puts forward an urgent demand for improving the ability of satellite-to-ground data transmission,which results in much pressure on X-band.The usable bandwidth of Ka-band is four times of X-band,which can promote the transmission capacity theoretically.At present,constant coding and modulation (CCM) and variable coding and modulation (VCM) are usually used in data transmission systems from LEO remote sensing satellites to ground stations.The improvement of channel conditions caused by the reduction of atmospheric attenuation when the elevation angle increases was not used,resulting in a waste of link resources.To solve the problem,for specific ground station and link availability,considering the characteristic that the free space loss and atmospheric attenuation decreased with the increasing of elevation angle,the VCM scheme of Ka-band based on DVB-S2（digital video broadcasting-satellite-2nd generation）was promoted,and the evaluation standard of transmission efficiency was given.The transmission efficiency of CCM and VCM at Kashgar,Beijing and Sanya stations with different rainfall characteristics at Ka-band was compared and analyzed,so as to find out the satellite-to-ground data transmission scheme for different ground stations.The simulation results show that the dry Kashgar station is more suitable for adopting CCM,and the link availability is as high as 99.82%.Beijing station with moderate rainfall is suitable for both CCM and VCM,and can be set according to users′ needs.However,Sanya station with abundant rainfall is more suitable for VCM,which not only makes the transmission efficiency factor increased by 8.37%,but also makes the link availability increased by 11.23%.

Key words: LEO remote sensing satellite, variable coding and modulation, application efficiency, data transmission, Ka-band, DVB-S2