Washington DC, Pasadena, CA: National Astronautics and Space Administration, Jet Propulsion Laboratory, 2005. Presumed First Edition, First printing, This is one of multiple originals issued. Poster. The format is approximately 8 inches by 10 inches. This is a single sheet, with printing/imagery on both sides, in a plastic sleeve. On the front side is a large color photograph of Earth's moon on the left side and a series of smaller photographs/images on the right, including Astronauts on the Moon, footprint on the moon, Craters, and a view of Earth from the Moon. The text on the reverse side has general descriptive narrative, Fast Facts, Significant Dates, and information about the images on the front. The Earth and the Moon form the Earth-Moon satellite system with a shared center of mass, or barycenter. This barycenter is 1,100 miles (about a quarter of Earth's radius) beneath the Earth's surface. The Moon's orbit is slightly elliptical, with an orbital eccentricity of 0.055. The semi-major axis of the geocentric lunar orbit, called the lunar distance, is approximately 250,000 miles or 1.28 light-seconds, comparable to going around Earth 9.5 times. The Moon makes a complete orbit around Earth with respect to the fixed stars, its sidereal period, about once every 27.3 days. Due to tidal locking, the Moon has a 1:1 spin–orbit resonance. This rotation–orbit ratio makes the Moon's orbital periods around Earth equal to its corresponding rotation periods. This is the reason for only one side of the Moon, its so-called near side, being visible from Earth. The plane of the Moon's orbit gradually rotates once every 18.61 years, which affects other aspects of lunar motion. These follow-on effects are mathematically described by Cassini's laws. More