In this chart, the low cost satellite tracking technique is compared to the
published and guestimated accuracies of the NAVSPASUR system. For the low cost
system, the position is determined to within 500m in a direction normal to the
fence mainly due to the accurately measured time of crossing and accurately
known fence location. Position in the plane of the fence is not well known
(+/-12 Km). The velocity uncertainty of 1% after the first acquisition amounts
to about +/-1 minute of time error in predicting the next pass 90 minutes later.
Even with a frequency uncertainty of a few hundred Hz, this is usually adequate
to identify the satellite on that next pass. After observing a satellite for
several days and refining the orbital element set, the velocity and positon
accuracies improve significantly. Acquisition and tracking of satellites
without use of any outside information has been demonstrated, and the capability
is within reach of amateurs.
