Let’s drop one of the lunar surface RR tests

See list attachedApril 15, 196969-PA-T-61APA/Chief, Apollo Data Priority CoordinationLet’s drop one of the lunar surface RR tests

During our review of the G Mission Lunar Surface Mission Techniques Document on April 10, we came to a conclusion which may interest you. It deals with the need, or really lack of need, for the crew to do some things that are in the current flight plan. Specifically, in the crew LM timeline, we have included two periods of LM rendezvous radar tracking of the command module – the first is two hours after landing and the second is two hours before lift-off. Neither of these periods are really needed although it may be interesting to try it once. On the other hand, it does require crew activity, uses electrical power, wears out the radar, and so forth and may even place a constraint on command module attitude during his sextant tracking of the LM. It was our conclusion that at least one of these periods of tracking should be eliminated and we are recommending that it be the first. The reason for deleting the first is that it interferes with the crew countdown demonstration (CDDT) for ascent, which is synchronized with the first CSM passage over the LM. If the crew were to perform rendezvous radar tracking, the CDDT would have to be terminated about 15 minutes before “lift-off.” By elimina- ting the rendezvous radar test, the CDDT can and should be run until about TIG minus one minute.

Although we are not proposing to delete it yet, it should be noted that the CDDT itself is of marginal importance and if it interferes with other more important activity, it could also be eliminated. It is not a precise countdown, anyway, since obviously the crew must not fire pyros, bring the APS batteries on line, pressurize tanks, and so forth, unless they really intend to lift-off. This CDDT should cer- tainly be eliminated from lunar landing missions after the first.

As noted in a previous memo, the command module sextant tracking of the IR is not mandatory either, although the flight controllers will use the data if they get it to reinforce confidence in their other data sources. And, of course, the post-flight people will undoubtedly find it interesting. Here again, though, it may be worthwhile to consider omitting one of the two sextant tracking periods. We are not proposing this yet either.