of roughly in the mid-to-late 1980s. In the early 1990s a French LLR system at the Observatoire de la Côte d’Azur (OCA) started operation, with similar precision. The McDonald and OCA stations are collecting data that is about as good as possible, given the number of photons that they collect back from the reflectors. Although minor improvements are possible, getting significantly better data requires a larger telescope and a better site. This is the basic goal of the APOLLO collaboration. The APOLLO laser has been operational since October 2005, and routinely achieves millimeter-level range accuracy between the Earth and the Moon. Science goals The goal of APOLLO is to push LLR into the millimeter range precision, which then translates directly into an order-of-magnitude improvement in the determination of fundamental physics parameters. Specifically, assuming improvements of a factor of ten over prior measurements, APOLLO will test: the Weak Equivalence Principle (WEP) to a part in , the Strong Equivalence Principle (SEP) to a few parts in , de Sitter relativistic precession to a few parts in , and the time variation of the gravitational constant G to a part in per year. Tests of the Equivalence Principles The Weak Equivalence Principle says that all objects fall the same way in a gravity field, no matter what they are made of. The Earth and the Moon have very different compositions—for example, the Earth has a large iron core, but the Moon does not. Furthermore, both are in orbit around the Sun, meaning that they are both falling towards the Sun at all times, even as they revolve around each other. If the Earth and the Moon were affected differently by the gravity of the Sun, this would directly affect the orbit of the Moon around the Earth. As closely as scientists can measure, the orbit of the Moon is just as predicted from assuming that gravity acts the same on each — to within 1 part in , the Earth and the Moon fall towards the Sun in exactly the same way, despite their different compositions. APOLLO will lead to even tighter limits. The Strong Equivalence Principle, according to Albert Einstein's general relativity, predicts that the mass of any object consists of two parts – the mass of the atoms themselves, plus the mass of the energy that holds the object together. The question is whether the energy portion of mass contributes