Éphéméride Lunaire Parisienne is a lunar theory developed by Jean Chapront, Michelle Chapront-Touzé, and others at the Bureau des Longitudes in the 1970s to 1990s.
The authors refer to it as a "semi-analytical" theory because they developed their expressions not purely symbolically, but introduced numerical values for orbital constants from the outset; but they also constructed partial derivatives of all terms with respect to these constants, so they could make corrections afterwards to reach the final solution.
[2] Even though ELP contains more than 20,000 periodic terms,[1] it is not sufficiently accurate to predict the Moon's position to the centimeter accuracy with which it can be measured by LLR.
[citation needed] An attempt was made to improve the planetary terms with the ELP/MPP02 lunar theory,[3] but heuristic corrections remained necessary.
[citation needed] A theory like the ELP has two advantages over numerical integration: Upon popular demand, the Chapronts also published ELP2000-85[4] and a book, Lunar Programs and Tables[5] with a truncated version of their theory and with programs, that could be used by historians and amateur astronomers to compute the position of the Moon themselves.