差分VLBI测量的一种实现方案

A Strategic Design of the Implementation of Differential VLBI

差分VLBI通过交替观测目标天体和参考天体,将共同的误差因素从观测量中扣除,能够实现高精度的相对定位,因而在深空探测中有重要作用。然而,差分VLBI高精度的实现要求目标天体和参考天体的角距很近,这大大限制了其应用。讨论设计了差分VLBI测量的一种实现方案,利用多颗参考源的观测内插出目标源的非几何时延修正,放宽了对目标源和参考源的角距限制。该方案在S波段对目标源非几何时延的修正精度可以达到1 ns水平。

Differential VLBI technique is alternatively observing a target object and a reference object by using VLBI technique. Subtracting the observed quantity of the reference object from that of the target object gives the differential observed quantity. This technique could result in very high relative position in precision because the subtraction removes most of the error sources from the observation of the target object, and so let the differential VLBI technique play an important role in deep space exploration. However, the application of differential VLBI is restricted due to the prerequisite that the angular distance between the target and the reference objects should be very small in order to maintain a high precision. In this paper, a strategic design of the implementation of differential VLBI is developed by using observations of several reference sources spreading out in a specially selected circular band and interpolating the non-geometric delay at the target object. Real data analysis of astrometric and geodetic VLBI experiments shows that by using our design a precision of about 1 ns in the correction of the non-geometric delay could be obtained at S-band.