See list attachedJune 5, 196969-PA-T-87APA/Chief, Apollo Data Priority CoordinationPRN ranging in lunar orbit is unnecessary
This memo is to restate our requirements for PRN ranging while in lunar orbit. I am writing it since there is evidently some confusion about it.
At no time in lunar orbit can PRN be classified as more than “desirable” – never “mandatory” or even “highly desirable” as long as things are going reasonably well. The only time ranging could become a requirement is if the entire trajectory determination system blows up and it is necessary to reinitialize from scratch when knowledge of the current state vector is essentially nil.
Since the specific questions arising recently deal with PRN requirements during powered flight – that is, ascent and descent, I would like to further state that during those periods PRN ranging is virtually of no use whatsoever. In fact, the powered flight processor in the RTCC will not even accept that type of data. Accordingly, if there is any advantage to be gained in configuring the spacecraft to exclude PRN during those periods in order to enhance the quality of other communication require- ments, I recommend that this be done.