Abstract: A method for sensing and monitoring ICBM threats using a constellation of earth orbiting satellites. The method includes arranging a first and a second plurality of threat sensing satellites in earth orbit. The first plurality is selected to have a first prograde orbit plane with a first inclination angle between about 30° to 70° with respect to the earth's equator and an Argument of Perigee equal to about 270°. The second plurality is selected to have a first retrograde orbit plane with a second inclination angle between about 110° to 150° with respect to the earth's equator and an Argument of Perigee equal to about 270°. The second inclination angle is selected to be a symmetric conjugate of the first inclination angle. The first and second plurality of threat sensing satellites are distributed respectively within the first prograde and first retrograde orbits with a Walker distribution of T/P/1.