See list belowJAN 17 196868-PA-T-13APA/Chief, Apollo Data Priority CoordinationNo change needed in the landing site determination programs – CMC or RTCC
1. During a Data Priority meeting a couple of months ago in which we discussed need for lunar landmark tracking, we uncovered what we felt to be a deficiency in the Colossus computer program. It was in the program which is used for determining the location of the landing site. Implicit in the program was the need for physically offsetting the optics from the associated known landmark to the center of the landing site itself. As a result, a program change request (PCR) was presented to the Apollo Spacecraft Software Configuration Control Board (CCB) on January 8 to correct this deficiency. It was felt to be a mandatory change based on the information available at that time although the precise ?????? of it had not been established.
2. On January 12 a group of Flight Crew, Flight Software, Mission Planning and G&C people (see attached list) met to discuss implementa- tion of this program change. Results of this meeting were certainly unexpected. Namely, it was concluded that the change was not needed at all and it was obvious that the CCB should be so advised. It is my understanding that MIT has not actually done any work yet and they have been notified of our conclusion. Some rather lousy operational procedures appear to be necessary during the lunar landing mission in order to do the job, and that is not as a result of any deficiency in this program. The remainder of this memo will be spent discussing those ???????.
3. ?????????????? targeting of the descent can only be performed on the ground, the rationale having been that without communications there would be no ??????? and with communications the ground could supply all ????????? information. Thus, the task to be performed is for the ground to be capable of determining the spacecraft state vector and ????????????? to ???????? consistent with one another based upon which it can perform the necessary spacecraft guidance ????????? computations. To do this it is necessary for the ground to obtain from the CSM ?????? observations of the landmark associated with the landing site. It really is immaterial whether or not the spacecraft is able to compute the landing site location; it is desirable that the spacecraft can compute the location of the associated landmark to assist in auto optics positioning but even this is not essential. The point is, the capabilities that are required are available within the program as it is currently written although it is probable we will utilize this program in a different way than the people who developed it intended.
4. The operational problems came about from a variety of sources. First of all, when the spacecraft is in an attitude permitting optical observa- tions of the landing site it is virtually certain the S-Band antenna cannot be directed toward the earth. This will probably cause concern for a number of reasons. The specific one which concerned us was that it would not be possible to obtain the optical observations on the downlink until the spacecraft had completed its pass and could be oriented to re-acquire S-Band antenna lock on. Even then it is only possible to get the observations on the downlink as the crew processes them one by one. Of course, this will also result in an onboard determination of the land- mark position, if that is worth anything. The procedure is further complicated by the fact that these observations—up to five of them, each one of which consists of 2 optics angles, 3 IMU gimbal angles and a time—are stored in erasable memory and are subject to destruction if proper program sequencing is not observed. For example, it will probably be necessary for the crew to orient the spacecraft and re-acquire S-Band antenna lock on manually since the computer programs which do that job probably share erasable memory with the navigation program. These may also be problems associated with timeline conflicts. For example, the spacecraft goes into darkness almost immediately after making these obser- vations and it is expected that a platform alignment will be required during the night time pass. Furthermore, for a westerly launch site, time between obtaining the observations and passing behind the moon is only about 15 minutes which will make it necessary to do these things very quickly. And to further complicate matters, it is probable that the LM has already been manned forcing one man to do it all by himself along with his many other duties.
5. I don't mean to be making a big deal of this, rather I am just trying to give some insight into the situation. In essence, programs as they are currently planned for both onboard and on the ground appear to be adequate. Fairly complicated crew procedures will be necessary and will be developed. Changes to the programs even if they were possible would probably not relieve the crew workload significantly.