of satellites in polar orbit at an altitude of 350 km referring now to the drawings fig1 shows that the line of sight from a satellite at an altitude of 350 km to the horizon is approximately 2000 km an omnidirectional sensor mounted on this satellite has a conical field of view of the surface of the earth and of the region above the surface of the earth that is defined by these lines of sight the overlapping fields of view of two such satellites in adjacent polar orbits provide stereoscopic coverage of activity of interest such as the launching of ballistic missiles within the region of overlap to minimize the number of satellites needed to provide a sufficiently continuous time continuous location ctcl stereo data relevant to a given threatened zone on the surface of the earth all satellites are placed in circular polar orbits as shown in fig2 that shows a constellation of eleven satellites 10 a through 10 k in respective polar orbits 12 a through 12 k around the earth the phases of satellites 10 are evenly staggered relative to each other by latitudinal u02dc 38 u00b0 which amounts to u02dc 4000 km denoted by u03b4 in fig2 additionally the orbits of satellites 10 of adjacent orbits 12 are separated in longitude by a common separation which amounts to u02dc 270 km on the equator this feature of the.