Test and Analysis of Frequency Stability of USO in YH-1

As an important milestone in the exploration of Mars in China,"YingHuo- 1",Chinese first Mars probe,is planned to be launched in 2011.The kernel payload of "YingHuo-1" is Ultra Stable Oscillator(USO) which provides frequency standard and transmits downlink signal.The ground-based radio Open-Loop-Doppler technology and VLBI system will be used to receive radio signal and support communication,navigation and tracking.In this article,the experimental data of YingHuo-1's USO is presented.Results show that the frequency stability of USO is about 1×10~(-12),which can support real-time precise orbit determination.