Sundisk range rate computation is not real accurate.

See list belowFEB 5 196868-FM-T-25FM/Deputy ChiefSundisk range rate computation is not real accurate.

1. As you know, one of the key parameters displayed during rendezvous is range rate based on the current state vectors in the computer. During our Sundisk Pre-CARR meeting at MIT on January 25, it was reported that due to approximations used in its computation, this parameter inherently has an error that can grow to as much as 5 fps. MIT has already reduced this error as much as they can by rectifying the solution every 100 seconds. Accordingly, it is my impression that the error grows over each 100 second interval up to as much as 5 fps, at which time it is reduced to zero again.

2. This deficiency, if I can call it that, seemed significant at first since the command module crew carries out their terminal braking schedule based on range and range rate. But considering the much larger errors we probably will encounter due to state vector inaccuracies, it will probably be lost in the noise which we had to be prepared for anyway. This note is just to make sure that everyone who is interested knows about this thing.