Development of an Architecture of Sun-Synchronous Orbital Slots to Minimize Conjunctions

Abstract

Sun-synchronous orbit (SSO) satellites serve many important functions, primarily in the areas of Earth reconnaissance and weather. The orbital parameters of altitude, inclination and right ascension which allow for the unique utility of Sun-sync orbit limit these satellites to a very specific region of space. The popularity of these satellite missions combined with the use of similar engineering solutions has resulted in the majority of current Sun-sync satellites within this region having very similar inclinations and altitudes while also spaced around the Equator in right ascension, creating the opportunity for conjunctions at the polar crossing points and a serious safety issue that could endanger long-term sustainability of SSO. This paper outlines the development of a new architecture of SSO zoning to create specific slots separating SSO satellites in altitude, right ascension and time at all orbital intersections while minimizing the limitations on utility. A methodical approach for the development of the system is presented along with the work-to-date and a software tool for calculating repeating ground track orbits. The slot system is intended to allow for continued utility of and safe operation within SSO while greatly decreasing the chance of collisions at orbital intersections. This architecture is put forward as one possible element of a new Space Traffic Management (STM) system with the overall goal of maintaining the safe and continued used of space by all actors.

Low Earth Orbit Slotting for Space Traffic Management Using Flower Constellation Theory

“…The limited work to date on LEO slotting has primarily focused on SSO. In 2007, the International Space University Summer Session Program produced a set of technical traffic and environmental rules that included a proposal for zoning of SSOs [13,[22][23][24][25][26][27] that was further developed in [14]. The authors mention the possibility of using specially-defined timing to allow for overlapping orbits, but do not present a technical system to determine such slotting.…”

Definition of Low Earth Orbit slotting architectures using 2D lattice flower constellations

“…The limited work to date on LEO slotting has primarily focused on SSO. In 2007, the International Space University Summer Session Program produced a set of technical traffic and environmental rules that included a proposal for zoning of SSOs (Anilkumar et al, 2007, 22-27) that was further developed in Weeden and Shortt (2008). The authors mention the possibility of using specially-defined timing to allow for overlapping orbits, but do not present a technical system to determine such slotting.…”

Slot Architecture for Separating Satellites in Sun-Synchronous Orbits

“…5 and explored in Ref. 6. Satellite constellations designed for other purposes have been reported in the literature; for example, the Walker constellation 7 was designed to provide good coverage of the Earth's surface with a limited number of satellites.…”