Cislunar
Cislunar Space
Cislunar space is the region of space extending from Earth to the Moon, including the volume surrounding both bodies and the five Earth-Moon Lagrange points (L1 through L5). In the 2058 setting, it contains the busiest transportation corridors in the Solar System and is home to the largest concentration of permanent human settlements beyond Earth.
The term comes from the Latin cis, meaning "on this side of." Thus, cislunar space lies on Earth's side of the Moon. The corresponding term, translunar, refers to travel toward or beyond the Moon, while interplanetary generally describes travel between planets.
Most routine commercial traffic in cislunar space passes through a network of Earth spaceports, Low Earth Orbit stations, orbital transfer stations, lunar settlements, and the Lagrange colonies. Thousands of chemical spacecraft operate within this region, while the smaller fleet of Nuclear Thermal Rocket (NTR) vessels usually continues onward to Mars, the asteroid belt, and the outer Solar System.
To a spacer, "cislunar" often refers less to a precise volume of space than to the developed inner transportation network surrounding Earth and Luna. Someone described as a cislunar pilot or cislunar engineer is generally experienced in Earth-Moon operations rather than deep-space travel.