Effects of polar motion on ICBM accuracy

Polar motion produces variations in several parameters employed in ICBM targeting computations which are traditionally treated as constants: earth's angular velocity vector, launch site gravity magnitude and astronomic coordinates, and target and launch site inertial velocities. The resulting targeting error is assessed for each of these quantities. The dominant error is shown to be the IMU azimuth alignment error which results in a cross-range miss as large as 50 feet. The effectiveness of pole prediction models is explored using pole position data for the period 1899 to 1982. An annually updated three-term sinusoidal prediction model is shown to reduce the crossrange miss by about 85 percent.