State Vector Update Criteria for AS-501

FA/Director of Flight OperationsJanuary 23, 196767-FM-4FM/Chief, Mission Planning and Analysis DivisionState Vector Update Criteria for AS-501

Because of the decision to utilize the AS-502 Apollo Guidance Computer programs for the AS-501 mission, the mission was designed and developed on the premise that the state vector updates would be made. ���������� this, the situation exists that a perfect launch vehicle spacecraft combination without guidance or propulsion errors of any kind will land about 225 nautical miles from the planned target. This is caused by the inaccuracy of the spacecraft navigation equations used on the onboard computer (see attached memo by Marlowe Cassetti). Another factor which affected the decision to base targeting on an updated vehicle and the inability to predict the time of the second S-IVB burn.

MPAD has been developing techniques and criteria to be used during the actual mission for making a decision on whether or not to send the up- date. The programs being developed to make this decision are manpower and time-consuming. I recommend, therefore, that we terminate this effort since the only possibility of not needing updates in the actual mission would be a chance combination of system errors in exactly the right combination to fall within the target ���������.

If this decision is accepted, therefore, it means that it is mandatory to send updates during the 501 mission and that the complete ground com- plex utilized for updating must be thoroughly verified before committing the ground system for flight operations.

Another item to note in the attached memo is the revelation that IMU errors greater than specification 3 sigma values may result in an un- acceptable heating test.

Enclosure