Trajectory and Spacecraft Design for a Pole-Sitter Mission

Abstract

This paper provides a detailed mission analysis and systems design of a pole-sitter mission. It considers a spacecraft that is continuously above either the North or South Pole and, as such, can provide real-time, continuous, and hemispherical coverage of the polar regions. Two different propulsion strategies are proposed, which result in a near-term pole-sitter mission using solar-electric propulsion and a far-term pole-sitter mission, in which the electric thruster is hybridized with a solar sail. For both propulsion strategies, minimum propellant pole-sitter orbits are designed. Optimal transfers from Earth to the pole sitter are designed, assuming Soyuz and Ariane 5 launch options, and a controller is shown to be able to maintain the trajectory under unexpected conditions, such as injection errors. A detailed mass budget analysis allows for a tradeoff between mission lifetime and payload mass capacity, and candidate payloads for a range of applications are investigated. This results in a payload of about 100 kg that can operate for approximately four years with the solar-electric spacecraft, whereas the hybrid-propulsion technology enables extending the missions up to seven years. Transfers between north and south pole-sitter orbits are also considered to observe either pole when illuminated by the sun.