An Evolvable Lunar Communication and Navigation Constellation Concept

NASA´s Global Exploration Strategy and proposed lunar architecture present a roadmap for future U.S. missions. The exploration plan begins with robotic precursor missions, followed by short human sorties, eventually progressing to a permanent base on the lunar surface. NASA´s Lunar Architecture Team concluded that this permanent base would be located near the lunar South Pole. The location of an outpost at the lunar South limits direct communication links with the Earth. A lunar relay element will be necessary to provide critical communication and navigation support for the upcoming missions. This paper presents a highly evolvable, low-cost lunar relay constellation concept using small satellites in Halo orbits about the Earth-Moon libration points L₁ and L₂. The initial constellation is designed to provide coverage of the lunar south pole in support of the inaugural robotic missions and is easily expanded to provide global coverage. Two satellites in an L₂ Halo orbit provide continuous South Pole coverage for the initial constellation. A final constellation providing nearly continuous global coverage can be achieved by the addition of two spacecraft in a Halo orbit about Li. A basic set of requirements and desired capabilities for the constellation is developed, based on NASA reports and Constellation C31 compatibility. A preliminary spacecraft bus and subsystems design is presented along with expected performance.