Feasibility of quasi-frozen, near-polar and extremely low-altitude lunar orbits

• Published in: Acta astronautica 2020-01, Vol.166, p.450-468
• Main Authors: Singh, Sandeep Kumar, Woollands, Robyn, Taheri, Ehsan, Junkins, John
• Format: Article
• Language: English
• Subjects: Altitude; Feasibility studies; Gravitational effects; Gravitational fields; Gravity; Image resolution; Impulsive-corrections; Low altitude; Lunar atmosphere; Lunar craters; Lunar Orbiter; Lunar orbits; Mission planning; Moon; Orbit insertion; Orbital maneuvers; Orbital mechanics; Orbits; Polar orbits; Quasi-frozen; Space missions; Spacecraft; Station-keeping; Sun
• ISSN: 0094-5765; 1879-2030
• DOI: 10.1016/j.actaastro.2019.10.037

Designing long-duration lunar orbiter missions is challenging due to the Moon's highly nonlinear gravity field and the third-body perturbations induced by the Earth, Sun and other large bodies. The absence of a Lunar atmosphere has offered the possibility for mission designers to search for extremely low-altitude, quasi-stable lunar orbits. In addition to the reduced amount of propellant required for station-keeping maneuvers, these orbits present great opportunities for unique scientific studies such as high resolution imaging and characterization of the polar ice deposits in deep craters. Prior to the GRAIL mission, mission planning for Lunar orbiters had suffered from inaccuracies, mainly due to the lack of an accurate Lunar gravity model, which resulted in severe deviations with respect to the spacecraft's nominal orbit. We study station-keeping feasibility for spacecraft in near-polar and extremely low-altitude, quasi-frozen orbits around the Moon, that are perturbed by a high-fidelity lunar gravity model and third-body effects from the Earth and Sun. For several candidate orbits, we compare the trade-space between mission duration and ΔV budget, considering impulsive maneuvers applied once every ‘N∈{2,6,10,14,18}’ orbits at periselene or aposelene. Additionally, we investigate the propulsive cost for different orbit insertion dates, the location of impulsive corrections for arresting argument of periselene (ω) drift, and controlling periselene altitude. •Analytical insights on ω variation drawn and specific trends for polar orbits reported.•Six extremely low-altitude (Periselene alt. ~ 20 km), quasi-frozen polar orbits are presented.•Investigation on optimal gravity of the Moon's fidelity model is conducted.•High-fidelity GRAIL model and third-body effects from Earth and Sun are considered.•Station-keeping analyses performed for different orbit insertion dates and maneuver points.