Space Regulatory Glossary Orbital Mechanics

Lagrange point

/ləˈɡrɑːnʒ pɔɪnt/ noun

1. One of five positions in a two-body orbital system (such as Earth-Sun or Earth-Moon) where the gravitational forces and the centrifugal force of the orbiting body balance, allowing a spacecraft to maintain a relatively stable position with minimal fuel expenditure.
2. The five Lagrange points (L1 through L5) are designated by their geometric relationship to the two primary bodies. L1, L2, and L3 are unstable equilibria requiring station-keeping; L4 and L5 are stable and can collect natural objects.

"The James Webb Space Telescope orbits the Sun-Earth L2 point, approximately 1.5 million km from Earth."

Origin Named after Italian-French mathematician Joseph-Louis Lagrange, who identified the L4 and L5 points in 1772.

Related terms

GEO Geostationary orbit. A circular equatorial orbit at approximately 35,786 km altitude where a satellite's orbital period… LEO Low Earth orbit. An orbit around Earth at altitudes between approximately 160 km and 2,000 km. halo orbit A periodic, three-dimensional orbit around a Lagrange point that traces a closed path when viewed from the primary…

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