针对采样返回任务中多探测器精密短弧定轨问题,研究了甚长基线干涉测量(Very Long Baseline Interferometry,VLBI)技术在两探测器间的交替观测模式、2π模糊度解算方法和数据差分处理方法,给出了星载信标的设计原则和方案.利用日本SELENE探月卫星的两个小卫星 R-star和V-star的同波束VLBI相关相位生成了交替VLBI相位观测量,对其进行了差分处理求解差分时延,然后利用差分时延和测速测距数据进行定轨计算.对差分时延的分析表明,交替VLBI差分群时延RMS值为46mm,测量精度与同波束VLBI差分群时延相当；交替VLBI差分相时延RMS值为1.6mm,测量精度与同波束VLBI差分相时延相当.定轨结果表明,交替VLBI在进行多探测器的短弧定轨时能达到同波束VLBI相当的精度.%To study the precise short-arc orbit determination for multiple spacecrafts in a sample-return mission, the VLBI switching observation mode, integer ambiguity resolution, differential process method and spacecrafts' signal requirements are investigated. Based on the same-beam VLBI cross-correlation phase, we produced the switching VLBI observation data, and calculated the differential phase between two spacecrafts to derive the differential delay. The precise orbits for each spacecraft are derived from the differential delay data. By comparing with the same-beam VLBI, we found that the group delay and phase delay of switching VLBI were as precise as that of same-beam VLBI, with the RMS of 46 mm and 1.6 mm respectively. If using Doppler/ranging data only, the accuracy of the 4-hour short-arc orbit determination is several hundreds meters. By combining the VLBI group delay data, the accuracy of short-arc orbit determination is improved to <75 m. Meanwhile, by combining the VLBI phase delay data, the accuracy of the short-arc orbit determination is improved to ~10 m.
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