Comparison of Precalculated Orbital Elements of the Army Explorer Satellites with the Actual Elements Derived from Observations

Based on precalculated data for the position and velocity vector of the injection points for the Explorers I through V, orbital elements are derived and compared with the actual orbital elements at injection time, calculated from position and velocity data obtained from radar measurements. Calculations are also made for the different orbital periods of a satellite perturbed by the Earth´s oblateness. For Explorer I, it is shown that the actual orbital elements derived from tracking observations agree well with the actual elements derived from early astronomical observations.