See list attachedJanuary 15, 196969-PA-T-8APA/Chief, Apollo Data Priority CoordinationF and G Lunar Orbital operations – mostly pre-DOI LM activation stuff
On January 10 we had an F and G Mission Techniques meeting dealing mostly with Lunar Orbital operations, which I would like to record with this thing.
In our continuing effort to figure out the best way to minimize the DOI day timeline, I think we have finally converged on the best basic procedure for getting the LM checked out. As usual we went over the three most popular ways proposed – namely:
a. All at one time on DOI day
b. Two work periods – one prior to LOI and one on DOI day
c. Two work periods – one on DOI day and one after LOI₂
We finally selected the last of these, basically by the process of elimination. Trying to do everything on DOI day not only lengthens that day by at least one hour but it also sets up a situation which is completely intolerant of even the most minor trouble as the crew goes through the process of manning, powering up, and checking out the LM. And, it should be emphasized that although it may be pos- sible in real time to slip DOI a revolution, it will be by no means a simple procedure to get all squared away again in preparation for the most complex operation we have ever attempted in flight. What I am trying to say is that we want to avoid perturbing the timeline around DOI at almost any cost and, splitting up the LM preparation into two periods helps to do this.
Having accepted the two period technique, the question remains – where to put the first period? Although the pre-LOI period of checkout was attractive for a number of reasons, it seemed to us questionable in terms on what it might do to the spacecraft thermal situation and more seriously to what might happen to the LM steerable S-band antenna if it were unstowed prior to the big SPS LOI maneuvers. Except for the fact that this time period provides continuous MSFN coverage, all other advantages are also obtainable if we schedule this activity after LOI₂. The thing we like about putting a two or three hour checkout period after LOI₂ and before the crew rest period is that it provides an opportunity for the crew to get the LM squared away – that is, things stowed and other housekeeping chores done before DOI day. It also provides an opportunity to add an additional activity which might be discovered during the D mission or as a result of con- tinued detailed planning of the F and G missions without perturbing the complicated pre-DOI timeline. (It also provides a place to stick in some F unique DTO's.) Of course, this checkout period is much more tolerant of problems than DOI day. For example, it can be extended although at the cost of some crew rest. And, perhaps more important, will provide more time for the MCC-H to evaluate and digest the checkout data. Charlie Duke is going to head a tiger team mostly composed of FCD and FCSD people to develop a detailed timeline for LM preparation including all those systems tests considered essential and no more than that. They will integrate these into the total timeline which includes the crew suiting and eating and all of the other LM activation activity as well as the CSM landmark tracking which now consists of only one tracking time period.
We will review the results of their work at a later Mission Techniques meeting so that everyone in the world can criticize it and finally bless it.
In addition to that one big item there were a pot full of little things we discussed and resolved as follows:
a. There is a minor difference of opinion between the F and G crew as to whether the landmark tracking should be done in the pitch or roll mode. John Young, who favored the pitch mode, is going to try out the other technique in an attempt to resolve this.
b. Most of us have pretty well agreed that docked AOT IMU align- ments are expensive to do and are not necessary. Accordingly, we now propose to use the same procedure as D for docked LM alignments referenced to the CSM platform using the known relative orientation of the CSM and LM navigation bases. This does mean that an accurate LM IMU gyro drift check can not be made although we expect it will be good enough for a go/no go of the system. Just how good it is will depend on how stable the relative orientation of the navigation bases is over a two hour period. We must get this information from ASPO as soon as possible.
c. Prior to and during DOI we want the LM radar turned on to check it out and if necessary to verify PGNCS performance of the DOI burn. After that the rendezvous radar may be turned off since there appears to be no strong requirement for its use until after the phasing burn on the F mission or until about five minutes before powered descent on the G mission.
d. In lieu of some other positive proposal we stated that the DPS would be separated from the ascent stage 10 minutes prior to the insertion maneuver by executing a 2 fps horizontal retrograde RCS burn. AGS control will probably be used for that.
e. It has been stated that there is very little difference in the accuracy of the results obtained using the sextant rather than the scan- ning telescope for landmark tracking therefore until C' it was proposed to use the telescope because acquisition and tracking was expected to be easier. However, the C' crew informs us that it is actually easier to track a given lunar feature using the sextant once it is acquired and so that is what will be done on the F and G flights.
f. Since there seems to be time available following LOI for the CMP to get some practice landmark tracking, it will be included in the time- line. Of course, the actual landing site will be in darkness then so some other feature located to the east must be used instead. It is our intention to select a landmark which will be at a 3 degree sun elevation angle on a nominal mission since this experience would give us a little more confidence of tracking at a low sun elevation angle. This benefit is not important enough, however, to make any real time change in the landmark to be used like we were prepared to do on C'.