See list attachedJUL 18 196868-PA-T-161APA/Chief, Apollo Data Priority CoordinationLM Ascent lift-off time can be determined by the crew
Some months ago we submitted a PCR to remove the pre-Ascent targeting program (P10) from Luminary and this was done. This action was based on an assumption that a simple crew procedure could be developed for doing the same job, in the event of loss of communications, making the rather complicated computer program unnecessary. The Lunar Mission Analysis Branch of MPAD has concluded their development and analysis of this technique and is in the process of documenting it. It is only necessary for the ground to supply two parameters by voice to the crew prior to DOI which will allow them to independently determine lift-off time to within about six seconds. This dispersion takes into account current estimates of MSFN accuracies, etc. The effect on the rendezvous differential altitude due to this error is less than one mile, which is certainly far smaller than other dispersions which would occur in a non-communication situation. In other words, it is more than adequate.
Quite simply the procedure requires that the crew determine the time of closest approach of the CSM one pass before lift off by noting the time rendezvous radar range rate passes through zero on the tape meter. To that time, he must add the CSM orbital period and another ΔT to obtain lift-off time. These are the two parameters included in the pre-DOI pad message noted above which will be determined by MCC-H based on the actual CSM orbit.