Lunar Ephemeris Polynomials

The Lunar Ephemeris Polynomials are used in the Virtual AGC to determine the location of the moon with respect to the earth during a lunar mission. This lunar position is used for several critical aspects of guidance and navigation of the CSM throughout the mission.

First, the lunar position is used by the AGC to account for the gravitational force of the moon on the spacecraft when it is in or near the moon's sphere of influence or SOI. Secondly, the position of the moon is used to make corrections to the spacecrafts state vectors independent of ground assistance, using the spacecrafts optical system. Finally, the lunar position can be used as a sighting mark to align the spacecraft to the universal coordinate system.

Form of the Lunar Ephemeris

The lunar ephemeris are stored in the AGC using a set of 3 9th order Taylor series of the form:

<math>X(t) &= x_0+x_1t+x_2t^2+\cdots x_9t^9 </math>