RES156 – 250 – Figure 1 below illustrates the definition of angle θ3. FIGURE 1 Θ a c d φb P where: a represents the earth station in motion b represents the boresight of the earth station antenna c represents the geostationary-satellite orbit (GSO) d represents the vector from the earth station in motion to the associated GSO FSS satellite φ represents the angle between the boresight of the earth station antenna and a point P on the GSO arc θ represents the angle between the vector d and point P on the GSO arc P represents a generic point on the GSO arc which angles θand φ are referred to. _______________ 3 In Figure 1 proportions are illustrative and not to scale.