See list belowFEB 8 196868-FM-T-27FM/Deputy ChiefSome Sundisk idiosyncrasies
1. Here are a couple of things we learned during the Sundisk Pre-CARR meeting at MIT on January 25 dealing with preparation to make a guided maneuver. One dealt with the procedure for updating the permanent state vector in the command module computer (CMC). As you know, the CMC idling program (P00) updates the state vector routinely based on the following test. When P00 is entered, it checks to see if the current state vector is older than 9 minutes. If it is, it causes it to be integrated up to the present time but if the time is less than 9 minutes (for example, 8 minutes and 45 seconds), it does not do anything except set a timer which will cause it to check the state vector age again in 9 minutes. Obviously, this means that if P00 is used to update it, the state vector can grow almost 18 minutes old. In preparation for some critical mission phases such as ???? in a thrust program, like P-40, it is necessary to bring the state vector up to date. Accordingly, it is recommended we utilize Verb 83 to do this as a standard procedure, since that procedure does not have the inherent uncertainty of P00.
2. The other matter dealt with use of the External Delta V program (P-30). As you know, targeting for P-30 is done impulsively, that is, 3 components of Delta V to be added at an instant of time. This time tag is ordinarily chosen to be the middle of the finite thrusting period. In order to compensate for orbital travel during this period, a rotation of the thrust vector is performed in the thrust programs (P-40). It was reported that if P-30 is ever entered after this rotation is done in P-40, it is done again on reentering P-40 doubling the rotation. Thus, if this program sequence is ever followed, as would happen if we updated the state vector after entering P-40, it would be necessary for the crew to reinsert the desired delta V's via the DSKY.
3. It was emphasized, however, that no harm is done by calling and recalling either P-30 or P-40; it is only when going back from P-40 to P-30.