APOLLO RENDEZVOUS NAVIGATION

摘要

The Apollo guidance, control and navigation system was designed by Draper Laboratory (nee the MIT Instrumentation Laboratory) during the mid to late '60's, but was the legacy of a series of earlier studies of Mars photographic reconnaissance missions which had been sponsored by the Air Force Ballistic Missile Division. The development of rocket engines and inertial measurement instruments was basic to turning the dream of poets into the reality of a trip to the moon, but on a narrower scale the development of practical guidance and navigation algorithms was enabled by the development of programmable digital computers and of higher order programming languages. In this paper we will focus in particular on navigation and guidance associated with the rendezvous of the Lunar Module with the Command Module as they orbited the moon. The rendezvous was accomplished with a sequence of thrusting maneuvers interspersed with relative measurements between the two vehicles. The Lunar Module had the primary responsibility for these measurements and maneuvers, but the Command Module had similar capabilities which could be used in a backup mode. The Lunar Module was equipped with a radar which supplied range, range rate, and two angle measurements. The Command Codule was initially to be equipped with only a sextant through which the Command Module pilot could sight the Lunar Lodule. These angular measurements were, in the end, augmented with a range measurement based on the communications link between the two vehicles. The rendezvous sequence began with the each vehicle observing the other using their respective set of sensors. After a short sequence of measurements the first of six maneuvers was performed. These maneuvers set up the Lunar Module in a coelliptic orbit below and behind the Command Module. After another sequence of sensor measurements an intercept maneuver was performed. This was succeeded by interspersed measurements and two midcourse correction maneuvers and finally terminated by a braking maneuver. At the end of this sequence the vehicles were in close proximity and the pilots manually maneuvered them to docking.