Review of Options for Autonomous Cislunar Navigation

During the early days of spaceflight, and especially during the Apollo program, significant advances were made in developing methods for navigation in cislunar space. Since then, new technologies and new data processing methods have been created that enable navigation options that were not available during the Apollo era. There are also new requirements associated with NASA's Constellation Program and the Orion spacecraft. Therefore, as NASA prepares to return to the moon, it is instructive to review the options, both new and old, available for cislunar navigation. By comparing the sometimes forgotten techniques used in the early days with the familiar techniques used on modern spacecraft, it is possible to make a more informed selection of the best navigation solutions for future missions to the moon.