SOLAR SURVEILLANCE ZONE POPULATION STRATEGIES WITH PICOSATELLITES USING HALO AND DISTANT RETROGRADE ORBITS

Abstract

Abstract Solar surveillance missions that provide ample warning time of impending solar storms to satellite users in earth orbit are naturally designed to allow the weather forecasting spacecraft to wander as far away from the earth as possible, in the direction of the sun. Vehicles positioned on the L 1 halo orbits do not provide more than an hour of warning time due to the fact that the L 1 equilibrium point of the sun–earth system is located at some 1.5 million km from the earth. In order to increase this warning time by a factor of two or more, use is made in this paper of distant retrograde orbits which allow compact sensorcraft to remain in the vicinity of the earth but at substantially larger distances from it than the L 1 point. However, the sensorcraft transit periodically and only for a limited time inside the surveillance zone centered on the sun–earth axis, such that a certain number of such sensorcraft is needed for continuous surveillance capability. An alternative scheme produces a finite number of passes through the surveillance zone with some transits reaching much further out toward the sun, over several years. Another scheme utilizes a series of miniature probes released from a multi-probe carrier vehicle from a parking halo orbit, to travel on that halo orbit invariant unstable manifold in successive single passes through the surveillance zone, requiring continuing replenishment. This paper shows several sensorcraft and sensor probes release strategies and their associated trajectories for both the distant retrograde orbit and the halo orbit cases. It also provides an estimate of the minimum number of probes needed for continuous coverage for a given time span.