RELATIVE PHASING AND OBSERVATIONS OVERLAP: LOW-THRUST TRAJECTORY DESIGN OPTIONS FOR THE INCUS MISSION

The INvestigation of Convective Updrafts (INCUS) mission, a recently selected NASA Earth Venture Mission, aims to enhance the understanding of the formation of tropical convective storms. After ejection from the launch vehicle in low Earth orbit, the three smallsats constituting the constellation will use their low-thrust engine to reach their nominal orbit formation for science operations. This paper outlines two aspects of the constellation design. First, the in-track offsets between vehicles are determined such that the ground observations are separated by a specified time interval. Second, an algorithm is developed to design the transfers sequence to deliver the spacecraft to their nominal configuration along the science orbit. Analytical solutions and approximations for both aspects are derived, allowing rapid design of the constellation’s initialization sequence. The proposed algorithm, labeled the double spiral transfer algorithm, is successfully employed to generate transfers that yield the nominal configuration for the constellation in a higher-fidelity model that includes atmospheric drag and spherical harmonics for the Earth’s gravity field. Multiple initialization sequences are constructed to examine the trade-offs between time-of-flight and propellant usage.