See list attachedJUL 26 196868-PA-T-169APA/Chief, Apollo Data Priority CoordinationJuly 9 and July 24 “G” Rendezvous Mission Techniques meetings
1. During the July 9 and July 24 “G” Rendezvous Mission Techniques meetings we have developed preliminary intra-vehicular rendezvous navigation sighting schedules. Crew work load estimates currently in use for the “D” mission rendezvous are included. These tracking schedules are very important since they have a predominating influence on almost everything else. For example, from these it has been possible to develop a preliminary spacecraft attitude time history which shows some fairly large gaps are going to be present in the CSM MSFN telemetry coverage. This, of course, is due to the fact that the S-band antenna is on the same side of the spacecraft as the sextant, which must be pointed down in order to observe the LM. Of course, during maneuvers ocurring within sight of the earth, the CSM can be yawed to a heads down attitude enabling S-band telemetry coverage. The rendezvous activities do not ordinarily interfere with LM telemetry coverage.
2. The Orbital Mission Analysis Branch (OMAB) of MPAD has distributed a memo (68-FM62-217, dated July 15, 1968) which presents the revised rendezvous profile including the relative motion plots and visibility and slant range time histories. Some of the most interesting features are:
a. Insertion occurs at approximately 340 n.m. slant range. By CSI this range will have decreased to approximately 170 n.m.
b. The LM will appear to the CSM to be less than 8° above the lunar horizon for the entire first two hours after insertion into orbit. After that, it will move below the lunar horizon.
c. There will be two points of sun interference for the sextant tracking of the LM, one immediately after insertion and another approximately two hours later, about 20 minutes before TPI.
3. OMAB presented the results of a study which shows that it is not possible to use the same maneuver solutions for LM maneuver targeting and CSM mirror image targeting on a lunar mission as is done on the “D” mission. Accord- ingly, if the CSM does not have CSI targeting capability in its computer, the LM crew will have to sequence through P72 to provide mirror image maneuver targeting to the CSM and then P32 to target its own guidance systems. If the CSM does have the CSI targeting programs, the LM crew will be relieved of this job and will use P32 only. The CSM pilot will pick it up since the nominal procedure would call for his determination of the LM maneuver targets using P72, which he would relay to the LM for PGNCS solution comparison and AGS targeting. He would then use P32 to compute his own mirror image maneuver. It appears that the TPI time used in the P32 and P72 computations may have to be different regardless of which spacecraft does it. Since the mirror image maneuver is to be executed with a one minute time delay after planned LM ignition time, it may also be necessary to change CSI time. OMAB is looking already into this.
4. There was considerable discussion regarding initialization of the LM PGNCS and CSM G&N for rendezvous navigation. As reported previously, platform alignments by both vehicles right after insertion are now included in the timeline. Upon completion of the CSM platform alignments, the MCC-H will relay a new LM state vector into the CMC based on LGC telemetry after insertion. Even with this update, it is anticipated that the uncertainties in these state vectors will be quite large, making it necessary to use initial values in the W-matrix which will not be suitable for W-matrix reinitialization during the rendezvous sequence. The Math Physics Branch is looking into that. We ended the meeting by starting the development of some “G” mission rendezvous ground rules and working agreements similar to those developed for “D”. Those we agreed to so far are attached.
5. The next meeting will be in September since many key people will be on leave during August.
July 25, 1968
“G” MISSION RENDEZVOUS GROUND RULES WORKING AGREEMENTS AND THINGS LIKE THAT
a. The reference trajectory is that provided by MPAD, dated August 15, 1968.
b. Nomenclature for the burn sequence following insertion is:
(1) CSI (2) CDH (3) PCI (4) TPI (5) TPF
c. The rendezvous will be run throughout with the vehicle roll angles ≈ 0°. The only exception to this is when during maneuvers within sight of the earth the CSM roll is 180°. TPI from above will be initiated “heads down” and TPI from below will be initiated “heads up” for either vehicle.
d. A LM state vector time tagged 12 minutes after insertion will be uplinked to the CMC within five minutes after insertion. State vectors are not sent to either vehicle again during the rendezvous phase.
e. IMU alignments will be made starting five minutes after insertion by both spacecraft and take precedence over the state vector update if timeline and/or attitude conflicts develop.
f. On both spacecraft all rendezvous navigation will be carried out to update the LM state vector. That is, the LM radar data will be used to update the LM state vector in the LGC and the CSM sextant and VHF data will be used to update the LM state vector in the CMC.
g. The CMC's LM state vector will be updated after each LM maneuver with the P76 Target ΔV Program using the pre-burn values as determined in the LM's pre-thrust program.
h. The state vectors in the AGS will be updated each time PGNCS is con- firmed to be acceptable. This will likely be at each time it is committed to make the next maneuver using the PGNCS except perhaps TPI.
i. AGC alignments will be made each time the PGNCS is realigned and each time the state vector in the AGS is updated from the PGNCS.