VLBI不仅对嫦娥三号在奔月环月段测定轨做出了重要贡献，刘庆会等还利用同波束VLBI把月球车的相对定位精度提高至20cm，并以5cm的灵敏度监视月球车动作。我国将发射由轨道器和火星车组成的火星探测器。捕获时，地火距离2亿km，与探月相比，星地距离增加数百倍，VLBI时延精度需大幅提高。另一方面，利用同波束VLBI技术观测火星轨道器和火星车，通过差分去除地球大气电离层影响，得到更高精度的差分时延数据,即可大幅提高定轨定位精度，又可创新性地开展火星大气电离层掩星观测研究。本项目将针对我国深空探测迫切需求，研究把VLBI时延精度提高至0.4ns的方法并攻克关键技术，如误差详细分析和改进措施研究、基于多普勒旋转的弱信号处理技术、相时延实时解算技术、基于GPS/水汽辐射计的大气时延改正技术、等离子体时延改正技术等。同时开展同波束VLBI技术在火星金星大气电离层掩星观测和环流特性的研究.

Very long baseline interferometry (VLBI) has played an important role in determining orbit in Chang'E series satellites. For example, VLBI much improved the accuracy of orbit determination on Chang'E-3 approach to the moon and circling the moon. We also performed the same-beam VLBI observations between the rover and the lander of Chang'E-3, monitored the rover motion with sensitivity of 5 cm, and measured the relative position between the rover and the lander with an accuracy of 20 cm. China will also launch Mars spacecraft, which consists of a rover and an orbiter, in 2018. The distance between Mars spacecraft and Earth is more than 200 million km, which increases hundreds of times compared with 380000 km of the moon, VLBI delay measurement accuracy must be greatly increased. On the other hand, using same-beam VLBI observations between the Mars orbiter and rover, the influence of the earth's atmosphere and ionosphere can be thoroughly canceled, and high-accuracy differential delay data can be obtained. These data not only can significantly improve the accuracy of orbit determination, but also can be used for innovative occultation observation researches in the Martian atmosphere and ionosphere. This project will focus on the researches of improving VLBI time delay measurement accuracy up to 0.4 ns and solving key techniques, such as detailed error analysis and improvement methods, weak signal processing technology using Doppler stopping method, technology of real-time decoding phase delay, atmospheric delay correction technique based on GPS and water vapor radiometer, plasma delay correction technology, etc. In addition，we will carry out advance research of Mars/Venus atmospheric and ionospheric occultation observations and orbit determination of the Mars orbiter and rover using the same-beam VLBI technique.