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[i]In a 2002 e-mail, Kranz elaborates, "Floyd's note was correct on the velocity-induced position error at the start of the descent. There were several interrelated navigation problems, i.e. known deficiencies in the R2 lunar (gravitational) potential model, down-track (along the flight path toward the landing site) and cross-track (left or right, perpendicular to the flight path) propagation errors (errors that start out small but become larger as the flight proceeds), and errors induced by maneuvering of the spacecraft. The principal error induced by maneuvering of the spacecraft was, however, the incomplete vent of the tunnel propagated over one orbit after separation. We made a change in all future missions to get a MCC go-nogo on tunnel delta P before giving the crew a Go to undock. Page 82 of the Apollo 11 post mission report says ...'because of uncoupled attitude maneuvers such as hot fire tests, undocking impulse, station keeping, sublimator operation and possible tunnel and cabin venting. The net effect of these perturbations was a sizeable down-range miss.' To my recollection, the trajectory reconstruction determined that with the exception of the tunnel venting, most of the other perturbations were essentially self canceling. Further the post mission review indicated that the delta P gauge was too gross, the markings misleading and the tunnel had to be vented earlier in the timeline and the valve left in the tunnel vent position rather than returned to off.[/i]
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