See list belowJUN 7 196868-PA-T-119APA/Chief, Apollo Data Priority CoordinationSome alternate ways of figuring out where the LM is on the moon will be available
For some months we have been concerned with the problem of determining the LM's location after its landing on the lunar surface. This information is essential in order to do a decent job of Ascent tar- geting and, in fact, a significant error can even influence crew safety. Primary modes already implemented in the Control Center/RTCC for determining LM location utilize observations of the LM with the CSM sextant and/or observation of the CSM with the LM rendezvous radar. In each case, these observations are combined with a knowledge of CSM location as determined by the MSFN to permit locating the LM. Another rather simple technique we have developed essentially uses procedures and computer programs already available to do the job in the same way a sailor at sea does. That is, we are able to determine the LM's location on the moon quite accurately by making an AOT plat- form alignment using the stars and by doing a gravity alignment which in effect establishes direction of local gravity and by then combining the information obtained. MPAD is in the process of formulating the equations to provide this capability in the RTCC and Charley Parker of the Flight Control Division will submit a request for the RTCC program change through the regular channels. We will also initiate a PCR to implement something similar in the Luminary computer program if it's as easy to do as we expect.
This not only gives a completely independent means (i.e., data source) for doing this job which is valuable for cross checking the prime tech- niques, but it also could become the prime mode under certain circumstances. For example, if it is necessary to abort one CSM revolution after landing, we would likely use this technique for determining LM location to target Ascent, since by that time neither sextant nor rendezvous radar data will be available to do the job.