During the early days of spaceflight, and especially during the Apollo program, significant advances weremade inndevelopingmethods for navigation in cislunar space. Since then, new technologies and new data processingmethodsnhave been created that enable navigation options that were not available during the Apollo era. There are also newnrequirements associated with NASA’s Constellation Program and the Orion spacecraft. Therefore, as NASAnprepares to return to the moon, it is instructive to review the options, both new and old, available for cislunarnnavigation. By comparing the sometimes forgotten techniques used in the early days with the familiar techniquesnused onmodern spacecraft, it is possible tomake amore informed selection of the best navigation solutions for futurenmissions to the moon.
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