There will be no VHF ranging data collected while tracking the LM on the lunar surface

See list attachedFebruary 28, 196969-PA-T-40APA/Chief, Apollo Data Priority CoordinationThere will be no VHF ranging data collected while tracking the LM on the lunar surface

It has been suggested that, in addition to optics and rendezvous radar tracking one spacecraft of the other while the LM is on the lunar surface, we should also utilize VHF ranging. This data would certainly be useful for post-flight analysis if not in real time. I have attempted to resolve the situation with regard to obtaining this data and have come to the conclusion that it is too late to get it, as unfortunate as that may be. The basic problem is in the formulation of the RTCC program. And, the program changes required appear to be too large for obtaining data which at best must be labeled “desirable.”

Through the years our plans for CSM tracking of the LM while on the lunar surface have all been based on just using the sextant. Obviously, we intended to use the Lunar Orbital Navigation program (P22), which not only provides automatic optics tracking but also complies the desired optical data, time tags, spacecraft attitude and landmark I.D. in a special downlist package for transmission to the MCC-H. The RTCC programs have been formulated to accept this data in that format and process it in real time.

First indications are that the spacecraft Rendezvous Navigation program (P20) would serve the crew as well as P22 for tracking the LM on the lunar surface with regard to automatic optics, and would have the additional advantage of including VHF ranging data on the downlist. Unfortunately, though, the P20 downlist format is substantially different than the P22 downlist and would require rather extensive changes in the RTCC program. For example, the sextant data is not stored in a batch of five observations as in P22 but would have to be stripped out one at a time as the observa- tions are obtained. This could easily cause us to miss some points. But more important, the RTCC would have to be coded to store them for processing. Finally, it is to be noted that P20 only collects a VHF data point once per minute – almost not worth the effort! Implicit in the above is that VHF telemetry via the CMC is the only source; raw VHF does not come down directly.

In summary, we are abandoning efforts to get VHF for the G flight. It may be worthwhile to put in a PCR to add VHF sampling to the P22 program and its downlist at a reasonable data rate. Jim McPherson – would you take the action on this, if it seems reasonable to you?