It's of cause fun to have this code to look at, but is it really useful? I don't mean it in a condescending way, but is this actually someone at, say SpaceX, looks at and goes: "Oh so that's how they did that"?
It's achingly beautiful to the pocket protector set (me!).
This source code, for example, contains the very first Kalman filter ever used - Kalman was invited over to Moffett field to give talks about his paper, which led to his theory was used in LM code. But I think everyone is very aware of the state of the art at the time, and things have advanced a lot since then. It is impressive to see them cramming that into such a limited processor. But, 'whatever' as to that aspect of it. This is a historical artifact of an amazing feat based on cutting edge research in mathematics/control theory.
It is my understanding that the AGC is the computer within the PGNCS. Terminology varies, as the last link below from NASA notes.
So far as I can tell, the AGC maintained the state vectors for the KF. Ground control would run batch mode least squares solutions, and pass it on to the LM, where the updates to the state vector would be applied by hand. I freely admit to not having worked through the code, but I believe the state vector update computations occur here:
http://www.ibiblio.org/apollo/listings/Comanche055/MEASUREME...
Thanks, that helps. I've always wondered what the variables of the state vector were -- position, velocity, etc. it appears from the link that it could be a 6x6 of those two (position, velocity in x, y, and z), or a 9x9 when including radar/landmark bias. Now I know!
- Today's processors and capabilities run circles around those of the Apollo. It might be interesting to know how they calculate a square root, not today.
- They have more sensors and inputs and have to think of new and advanced ways of making it all work together
