GPS的空间应用

由于ＧＰＳ系统的特点以及低轨道空间的特殊应用环境，使得ＧＰＳ在空间上的应用存在着与地面应用所不同的特点，本文着重分析这些空间特点对ＧＰＳ定位实现的影响，得出以下结论：对空间用户而言，ＧＰＳ卫星对用户的覆盖有着不同于地面的特点，但可以看出，对９００公里高度以下的低轨用户，ＧＰＳ卫星对用户的覆盖不会比地面更差。同时，电离层延迟误差影响大大降低，对流层延迟误差可以不予考虑。ＧＰＳ系统本身已对相对论效应的长期项影响作了校正，但对空间用户必须重新考虑。由于空间用户运动的规律性，及我们可能对诸如信号的Ｄｏｐｐｌｅｒ频移，多路径干扰等成份作较为准确的估计并加以补偿，从而可能获得高于地面的测量精度

THE APPLICATION ENVIRONMENT OF GLOBAL POSITIONING SYSTEM (GPS)IN THE SPACE

With the development of GPS and its applications, the concept of using Global Positioning System (GPS) for space navigation is put forwards. GPS application has been extending to the space, but little is known about the influence of the space environment to GPS perforrmance. In this paper, we discussed the influence in detail, and get the following conclusions. For the space user, the coverage of GPS SV S is different from that for a ground user. But for the orbit below the height of 900Km, the coverage is not worse than that for a ground user. The ionospheric delay error largely decreased in the space, which make the errror of model correction decreased, the tropospheric delay can be taken out off consideration. GPS has adjusted the frequency of SV according to the long-term effect of relativity for the ground user. For the space user, the relativity effect must be reconsidered. Furthermore, the regularity of the move of the space user make it possible to model some variables, such as the Doppler shift, multipath interference in GPS signal, and to compensate to achieve a better precision.