F Rendezvous Mission Techniques

See list attachedNovember 15, 196868-PA-T-252APA/Chief, Apollo Data Priority CoordinationF Rendezvous Mission Techniques

We had our first F Rendezvous Mission Techniques meeting on November 12. We went through the whole thing rather smoothly with very few open items, probably due to all the past work on D and G. Obviously it is a much simpler exercise than the D rendezvous. This memo is to record a few of the significant agreements. Many more were reached but have been understood for some time and are not considered particularly controversial. Attached is a list of action items assigned to MIT.

1. The CSM Separation maneuver from the LM an hour before DOI shall be radially downward 2.5 fps.

2. We intend to use identical REFSMMAT in the CSM and LM. It will be computed by MCC-H at the beginning of the DOI period of activity and will not be changed throughout the entire rendezvous. In fact, it will probably be used for TEI as well. It is keyed to the pseudo-landing site and will not incorporate information obtained by later orbit determination or by optics observations of the pseudo-landing site – just like G.

3. Both the DOI and Phasing maneuvers shall be targeted from the MCC-H, of course. This will be done prior to DOI and relayed to the crew as a maneuver pair. We do not intend to update the spacecraft state vectors between DOI and Phasing from the MCC-H. However, a period of rendezvous tracking and navigation has been tentatively scheduled for about 30 minutes during that period.

4. The CSM will be targeted and counting down to make the first maneuver of a Hohmann transfer to a 20 n.m. circular orbit if the LM becomes inactive at phasing. The command module will also be prepared to execute a mirror image type maneuver when the LM executes the Insertion burn which starts its duplication of the lunar landing mission rendezvous.

5. Targeting for the Insertion maneuver will be updated in real time from the MCC-H, designed to achieve a 15 n.m. differential attitude during rendezvous. There is some question, however, if this targeting is to be based on MSFN tracking or on state vectors as determined onboard by rendezvous navigation during the phasing orbit.

6. We were not able to conclude much with regard to AGS operation since it is not clear what computer program will be available for the F mission. We hope to know what its capability will be about November 15. Of course, we are assuming that the primary guidance systems will be using COLOSSUS II and LUMINARY.

7. Just as is planned for the G mission, we intend for the MCC-H to relay the LM state vector obtained by telemetry following the Insertion maneuver back to the CSM. This will be followed by REFSMMAT alignments by both spacecraft.

8. The CSM will use its P30 series rendezvous targeting programs both for its own mirror image targeting and for relay to the LM. In order for the LM to compare solutions, it will be necessary to include certain bias on the maneuvers as determined pre-flight due to the errors induced by using P30's rather than the P70's and also because of the one minute time delay in TIG (for example, at 1.5 fps, bias is required on CSI). It is intended that the CSM backup CSI, CDH, and TPI using the SPS. Incidentally, it is intended to use LM +X RCS for CSI and +Z RCS for CDH and TPI.

9. As planned for G, we are labeling the CSM maneuver targeting as the “yard stick” for LM maneuver verification in real time. This is based on our belief that it is possible to independently verify GNCS performance in real time – something we can't do with the LM PGNCS.

10. We had our usual discussion regarding tolerable TPI time slip. It appears that with VHF ranging, the TPI window is quite large – perhaps ± 15 minutes or so. If this is the case, we should have very little problem. FCSD has accepted the task of determining just what the window is and of defining precisely the optimum location of TPI. MPAD will determine the anticipated three sigma TPI slip. The point that really counts though is that we should never have to abandon the TPI elevation angle option in favor of the time option and we are to carry out our plan- ning based on that assumption. Incidentally, there is complete agreement that we must use two elevation angles for TPI. One for approach from above, the other from below just as was planned for G.

11. There may be some problem associated with recording LM low bit telemetry in the command module on the back side of the moon if someone really wanted to do that. It apparently conflicts with simultaneous VHF ranging which we consider mandatory. Whoever wants this data will have to look for some other substitute for a LM tape recorder, it seemed to us.

12. Our next meeting will be in a month or so. We'll firm up the tracking schedule and will list the equipment we feel required to continue at each milestone in this exercise at that time. Something else we'll try to get squared away by then is all the “mickey mouse” required to get landing radar data at the same time we are doing the Phasing burn! And, we need to pin down the burn monitoring procedures to the Phasing and Insertion maneuvers.

Enclosure

MIT ACTION ITEMS FOR F RENDEZVOUS (November 12, 1968)

1. Is the Target ΔV going to be or has it been changed from a routine (R32) to a program (e.g., P76) in LUMINARY? If not, why not?

2. What program sequence choices have we for getting landing radar data on the downlink just before the Phasing burn?

3. What program sequence should be used for the APS Insertion burn preceded by DPS staging to insure proper RCS attitude control by the DAP?

4. What is the cost of slipping TPI execution in COLOSSUS without updating TIG?

Enclosure 1