See list attachedFebruary 11, 196969-PA-T-23APA/Chief, Apollo Data Priority CoordinationF/G Mission Techniques – except for the lunar orbit phase – are ready to eat
Some of the decisions and open items that came out of our F/G Mission Techniques meetings in late January are listed in this memo. Basically, I would say that all mission phases aside from the lunar orbit activity are very well understood at this time – primarily as a result of the C' mission – and should be formally documented within the next couple of weeks.
1. Flight Control Division is going to establish the detailed procedures for manning and activating those LM systems required to establish communications in the unlikely event CSM communication is lost. They must include the techniques for orientating the LM steerable antenna toward the earth if the omnis are inadequate. It is also neces- sary to give some thought to when the crew should initiate these procedures. That is, what should be done with the CSM communication systems first after the total failure seems to have occurred.
2. As a standard procedure, MCC-H will update CSM state vectors on a more-or-less periodic basis – say every 10 hours or so when it is mutually convenient to the crew and ground, unless they have changed so little as to make it useless. Whenever the state vectors are updated, it will be to both the LM and CSM computer memory slots, CSM first.
a. The launch REFSMMATS will be retained until the IMU alignment after MCC₁ time whether the maneuver is made or not.
b. The same PTC REFSMMAT will be used translunar and transearth during the periods from the post-MCC₁ to pre-MCC₄ and from TEI plus two or three hours to EI – 5 hours.
c. The lunar orbit REFSMMAT to be used for the period between the PTC times defined in “b” shall be such that the LM in landing attitude, over the landing site after DOI would have 0, 0, 0 on the FDAI. This REFSMMAT will be computed by the MCC-H prior to MCC₄ for use in the CSM. According to my notes, the REFSMMAT will be updated on DOI day to com- pensate for prediction uncertainties. I can't remember why. (On the G mission, of course, the REFSMMAT in the LM will be updated several times automatically while on the lunar surface by the LGC to correspond to the ascent alignment. Currently we plan to update the CSM more or less to the ascent REFSMMAT but we will not attempt to maintain it precisely the same as the LM.)
4. The only burn monitoring limit it is necessary to change from those used on C' is the one used for overburn protection on LOI₁. The extra mass of the LM makes this maneuver substantially longer in duration, so that limit has been made correspondingly larger. Specifically, it will be 10 seconds rather than 6 seconds.
5. Math Physics Branch was requested to determine if in order to maintain a good MSFN orbit determination capability, it is really neces- sary for the crew to reverse the orientation of the spacecraft x-axis every three hours during periods of venting. It seems as though the net effect of the venting is almost exactly in the least sensitive direction when using the PTC attitude currently proposed and it would certainly be nice to avoid unnecessary spacecraft maneuvers; perhaps even unnecessary awakening of the crew.
6. In order to insure that the crew never experiences CMC Program 65 during entry, MCC-H will make a real time selection of entry range to avoid P65 prior to targeting TEI. This should not be a difficult thing to do while in lunar orbit but cannot be done pre-mission to suit all launch opportunities.
7. The crew is looking for a recommendation as to whether the entry should be performed using one or two RCS rings. Claude Graves is said to be working on this.
8. Docked DPS burns in lunar orbit
a. It was established that, if a docked DPS burn is to be used for TEI, it should be carried out with one burn only as opposed to two as has been suggested.
b. In this event the LM platform will be aligned using docked AOT sightings of stars in order to determine platform orientation (P51). Given the accuracy of pulse torquing, it will be possible to reorient the IMU for the maneuver without additional AOT sightings.
c. The CSM will use the Average G Program (P47) for maintaining state vectors if we make a docked DPS burn.
d. It was estimated that the LM could be made ready for such a burn easily within 1½ hours.
e. MIT was asked to determine if the DPS gimbal trimming would work in the docked configuration at 10 percent thrust in the LUMINARY program.
f. It is evident that complete docked DPS check list must be prepared for the F and G crews by FCSD.
9. The crew was somewhat concerned with the technique MPAD has developed for the LOI-15 minute abort. This abort maneuver, you recall, is one the crew must target for themselves in the event of a premature SPS shutdown during LOI. The crew charts that MPAD has developed present the ΔV required assuming the maneuver will be executed exactly 15 minutes from the time of SPS shutdown. Since the spacecraft clocks are all keyed to LOI TIG, the crew feels it would be easier for them if the maneuver were scheduled to occur 15 minutes from LOI TIG. The point is, they were concerned that in the event of an emergency they may not note the time of shutdown or are more likely to make a mistake in determining when to execute the abort maneuver. Flight Analysis Branch, MPAD, is looking into reworking these charts based on TIG rather than SECO.
10. Since there is concern over premature shutdown on either the LOI or TEI maneuver, the crew asked if it were not logical to protect against it, particularly in the unstable butterfly region, by use of the Thrust Direct On switch. For example, during LOI they suggest turning that switch On from TIG + 1 minute to TIG + 5 minutes and on the TEI maneuver they would switch it On from TIG + 15 seconds to TIG + 2 minutes. Flight Control and other guys are going to think about that! I think the greatest fear is what would happen if the crew neglected to switch it off in time.
That's all I can remember. Mostly trivia, you see which probably shows better than anything the status of F/G Mission Techniques for these mission phases.