# How did the Apollo guidance computer handle the Earth-Moon system's rotation around the Sun?

In this comment I just wrote:

"...but at all other times it is just doing math to calculate its trajectory." The math needed a stable clock Timing accuracy of the Apollo Guidance Computer? (also 2, 3) and an ephemeris to look up the positions of the Earth and Moon as a function of time to calculate which way their gravitational accelerations are pointing.

But now I wonder how the Apollo guidance computer software accounted for the motion of the Earth-Moon system's orbit around the Sun during the few days the astronauts spent traveling between the two.

1. Did the software have a look-up table for the position of the Earth-Moon barycenter relative to the Sun?
2. Or was there just a centrifugal pseudo-force term based on an average distance to the Sun?
3. Or something else?
4. Or nothing at all?

• +1 Great find, thank you! I just did a quick look and at least one of the uses of the position of the sun is in P51-P53.agc for purposes of ruling out stars that may not be visible due to interference by the Moon and the Sun, so as you mention it still remains to be seen if and if so, how the Sun's position might have been used in orbit propagation. – uhoh Feb 19 at 13:56