日本SELENE月球探测计划和卫星间多普勒跟踪的数学模型

SELENE Mission: Mathematical Model for SST Dopler Measurements

日本月球探测计划（ＳＥＬＥＮＥ）定于２００４年夏季利用ＨＩＩａ火箭发射一组共３颗绕月人造卫星。他们是主卫星、跟踪中继卫星和空间ＶＬＢＩ电波源。其主要科学目标之一是利用对绕月卫星的多普勒跟踪数据精确测定月球重力场，研究月球的起源与演化。ＳＥＬＥＮＥ计划中实现这个科学目标的关键技术是引入中继卫星，目的在于当处于低轨道的主卫星飞行到月球背面地面观测站无法观测时，采用卫星间跟踪方法（ＳＳＴ），建立地面站与主卫星之间的联系，以得到月球背面重力场的直接测量数据。介绍了几种典型的四程卫星间多普勒跟踪模式和相应的数学模型，并针对ＳＥＬＥＮＥ计划中采用的特殊四程多普勒跟踪模式建立了卫星相对观测站速度与跟踪信号多普勒频移之间的转换关系。提出了利用 ＧＥＯＤＹＮ ＩＩ定轨分析软件处理ＳＥＬＥＮＥ多普勒跟踪数据的流程。

Japanese lunar exploration mission, SELENE, has been planned to be launched into space by using H II-a rocket in the Summer of 2004. This mission is composed of 3 subsatellites, a main lunar orbiter, a relay satellite and a free flying VLBI radio source. One of its main scientific objectives is the estimation of high order and degree spherical harmonic coefficients for the lunar gravity field. Different tracking methods will be employed in SELENE. The key tracking method is 4 way Satellite-to-Satellite Thacking (SST) technique. By this way, the tracking data can be obtained through the relay satellite when the low altitude main orbiter is flying at the far-side of the Moon and can not be'seen' from the Earth. To success the historical tracking data, a complete coverage of Doppler traking from an orbiter at sufficiently low altitude with high tracking accuracy can be obtained. The 4 way SST has various configurations. For SELENE, The SST tracking mode is introduced here, the mathematical relation between range rate and 4 way Doppler count number is established, and a data processing stream frame by using GEODYN II is suggested.