基于CEI的飞船交会对接远程导引段的轨道确定方案

探讨了CEI技术在飞船交会对接远程导引段的高精度定轨与实时监控的能力。仿真结果表明:精密定轨中采用可视弧段较长的单站可使相对位置精度达百米以内,速度达厘米/秒级。采用单一绝对扩展卡尔曼滤波器的方案进行实时轨道计算,采用滤波稳定后固定模糊度的方法可以使相对轨道位置精度达十米级,速度精度达厘米/秒级,事后及实时的轨道精度均满足远程导引段的精度指标。     

Delta-v requirements for earth co-orbital rendezvous missions

Earth co-orbital asteroids present advantages as potential targets for future asteroid rendezvous missions. Their prolonged proximity to Earth facilitates communication, while their Earth-like orbits mean a steady flux of solar power and no significant periodic heating and cooling of the spacecraft throughout the course of the mission. Theoretical studies show that low-inclination co-orbital orbits are more stable than high-inclination orbits. As inclination is the most significant indicator of low delta-v rendezvous orbits, there is the potential for a large population of easily accessible asteroids, with favorable engineering requirements. This study first looks at phase-independent rendezvous orbits to a large number of objects, then looks in more detail at the phase-dependent orbits to the most favorable objects. While rendezvous orbits to co-orbital objects do not have a low delta-v necessarily, some objects present energy requirements significantly less than previous rendezvous missions. Currently we find no ideal co-orbital asteroids for rendezvous missions, although theoretical Earth Trojans present very low-energy requirements for rendezvous.     

The statistics of flight opportunities to accessible near-Earth asteroids

A statistical study has been carried out of the availability of favourable flight opportunities to near-Earth asteroids with orbits similar to the Earth's. Emphasis is given to rendezvous-type mission profiles employing two-burn impulsive transfers. Velocity-optimized Lambert trajectories for a sample of 27 actual objects were calculated and compiled in a database. The velocity and flight time statistics of the resulting 1200 different solutions covering a period of 11 years have been investigated and discussed. Comparison with typical flight profiles to the Moon and near planets has revealed flight opportunities to 5 objects within a decade from the present requiring less ΔV than favourable flight opportunities to Mars or Venus. One of the objects involved, 1999 AO10, can be rendezvoused with using a total velocity increment that is smaller than that required to establish a lunar orbiter. The use of slow flybys for the most scientifically appealing targets is illustrated through an example trajectory involving the C-class binary object 1996 FG3. The challenges and opportunities for doing science in proximity to such small objects are also discussed.