where [] is the distance between the i th and kth elements, and 0 is the scan angle, i.e. the angle of incidence of the pilot signal (Figure 10). In Appendix A we show that the transmitted beam points in direction 6’ given by which gives Eq. (8) is just the squint error, Eq. (4), due to the two way doppler shift, (7) (8) To get some idea of the magnitude of this error, apply (8) to the SPS ARA described in Sect. I. Its allowable pointing error is 5.6 x 10^-6 radians. Therefore, assuming |o| £ 45 degrees (much larger than the scan angles specified in ARA preliminary designs, (8) gives The actual radial velocities of geosynchronous satellites are much smaller than this (less than 1.0 m/sec in most cases), so we need not worry about "doppler squint" in this case. Deep space probes, on the other hand, may travel much
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