Downthread: List of “D/E” Rendezvous open items (Apr 16, 1968)
See list belowMAR 7 196868-PA-T-55APA/Chief, Apollo Data Priority CoordinationFirst “E” Mission Rendezvous Mission Techniques meeting – March 4
1. On March 4 we had the first “E” Mission Rendezvous Mission Techniques meeting. It was devoted almost exclusively to understanding what the mission requirements and mission plans are for this phase of the flight. The discussion raised a few questions and some action items were assigned to get them answered.
2. It is evident that activities prior to the rendezvous such as the big S-IVB maneuver simulating translunar injection (TLI) will substantially perturb conditions at the start of the rendezvous unless compensation is provided. This, of course, means that the logic and capability to plan this “compensation” in real time must be designed and implemented. Ed Lineberry and his people were asked to look into this. (They're doing a similar job for Mission “D” already.)
3. The “E” mission is typical of any involving LM operations. It starts with an undocking and visual inspection. This is followed by a small RCS maneuver by one vehicle or the other to provide a controlled mini-distance separation trajectory to avoid costly station keeping. This is followed in turn by a larger separation maneuver which kicks off whatever is to be done. In this case, the larger separation maneuver, called a “Phasing maneuver”, places the LM ahead and above the command module properly located to execute the CDH coelliptic maneuver about 2 hours and 40 minutes later. It is intended that these Phasing and CDH maneuvers will be computed in real time in the RTCC utilizing the so-called NCC/NSR rendezvous maneuver logic developed for Gemini. This targeting will force the CDH maneuver to occur at spacecraft apogee over Hawaii, with the proper differential altitude and phase angle.
4. The entire rendezvous will be carried out with a single inertial platform orientation (REFSMMAT) for each spacecraft. They will be computed and relayed to the spacecraft from the ground. Of course, more than one platform alignment will be performed. The point is they will all be carried out to achieve the same inertial platform orientation. Furthermore, it is anticipated that the REFSMMAT on Mission “E” will be selected essentially the same as for the “D” and “G” missions. That is, they will be tied to TPI and will provide an FDAI 8-ball display of 0, 0, 0 when the spacecraft is aligned in-plane, horizontal, wings level, heads up.
5. It was agreed that an undocked platform alignment would be made between the separation and Phasing maneuvers. In order to permit this we established that separation will occur 5 minutes before the start of the darkness period prior to the Phasing maneuver. Since this will result in almost a complete revolution between the separation and Phasing maneuvers a small radial separation burn such as planned for missions “D” and “G” may now work out too well here, and the Rendezvous Analysis Branch was given the action item of selecting an optimum separation burn to be illustrated at the next meeting with the standard relative motion plot. Flight Planning was requested to work out the crew timeline in detail for the period between undocking and the Phasing maneuver. We want to make sure that the various crew activities associated with LM checkout and trajectory control do not conflict nor are unduly crowded. I'm sure someone will also be interested in determining the consumables required during this period since apparently both electric power and RCS propellant are at a premium.
6. Finally, the crew procedures people were requested to evaluate and report at the next meeting the preferred lighting conditions for the TPI maneuver when it is executed by a spacecraft approaching from ahead and above. This will be the situation for the first TPI opportunity on the “E” mission. Although that maneuver would not actually be executed as long as everything is still going along okay, we should be prepared to do it if we have to. And the preferred lighting conditions influence scheduling of the Phasing maneuver itself.
7. The current rendezvous plan provides two opportunities to perform a CSI maneuver, both of which are nominally zero. However, it was questioned as to whether the first opportunity really exists since it occurs only 36 minutes after the Phasing maneuver with insufficient ground tracking and communications to support it. It may be desirable for the crew to perform rendezvous navigation and target this maneuver; the question is whether they would ever really execute it. The point is, if it turns out to be small there seems to be no disadvantage in delaying until the next CSI opportunity one revolution later, and if the onboard systems indicate that a large CSI maneuver is needed there is reason to suspect some system malfunction. This is based on the assumption there had been no indication of non-nominal performance during the Phasing burn, which implies that CSI should be near zero. It seems we ought to obtain some MSFN confirmation before making a big burn that might screw up the situation. In conjunction with all this, the Rendezvous Analysis Branch was given the action item of determining parametrically the effects of residuals in the Phasing maneuver in terms of CSI maneuver magnitude and other trajectory dispersions such as TPI time slippage.
8. It has been stated that a primary mission objective on this flight is to perform a comprehensive AGS systems test. This, of course, must involve rendezvous navigation and targeting as well as maneuver guidance and control. This can be done in a number of ways. For example, the AGS could be allowed to operate continuously without PNGCS update throughout the entire rendezvous exercise. Or the test could be broken down into a number of individual tests with re-initialization provided periodically. It is also necessary to specify when and under what conditions radar data should be input into the AGS. G&C Division was requested to amplify their mission requirement by providing a more detailed description of exactly what they would like accomplished and if possible how they would like to do it.
9. That is about all we covered during this short meeting. Once nice thing apparent was the substantial carryover from the “C” and “D” mission techniques meetings which should permit us to complete work on “E” in a considerably shorter period than would otherwise be the case. it was agreed that Monday afternoon is a good meeting time and so, if possible, we intend to get together every other week at that time. The next meeting is scheduled at 1:00 p.m., March 18, in Building 4, Room 396. That's 1300 for you, Frank.