吉布斯定轨法。

输入：轨道上任意三个点的位矢(R1,R2,R3)；

输出：质点在R2端点时的速度V2；ierr是个判断符号，返回的ierr是零的话，就说明‘R1,R2,R3’共面，如果ierr是1的话说明‘R1,R2,R3’不共面(正常情 况下，要构成轨道的话，‘R1,R2,R3’一定共面 ，即ierr是零，如果ierr是1的话说明输入的‘R1,R2,R3’不共面不能构成轨道。

此函数用于：任意给定三个空间共面的向量，可以确定质点在R2处的速度V2，也就得到了轨道上的一个状态向量(R2,V2),调用前面的函数就可以确定其轨道，及任意时刻的状态。-Gibbs set the track method. Input: track any three points of the bit vector (R1, R2, R3)　output: particle at R2 endpoint speed V2,　ierr is a judgment symbol, The ierr that is returned is zero, then, it means'　of R1, R2,, R3, ' coplanar, if ierr is 1, then descr iption'　of R1, R2,, R3, ' not a total surface (under normal circumstances, you want to constitute a track, then,'　of R1, R2, R3, ' a certain total surface, ierr is zero, if ierr is an instructions to enter the words ' of R1, R2, R3'　coplanarity can not constitute a track. This function is used: for any given three space vector of the surface, can determine the particle at the speed V2, R2 also track a state vector (R2, V2), call the previous function can determine its orbit, and at any time of the state.