In August 1960, NASA launched its first communications satellite, Echo 1. Fifty years later, NASA has achieved another first by placing the ARTEMIS-P1 spacecraft into a unique orbit behind the moon, but not actually orbiting the moon itself. This type of orbit, called an Earth-Moon libration orbit, relies on a precise balancing of the Sun, Earth, and Moon gravity so that a spacecraft can orbit about a virtual location rather than about a planet or moon. The diagrams below show the full ARTEMIS-P1 orbit as it flies in proximity to the moon.
ARTEMIS-P1 is the first spacecraft to navigate to and perform station keeping operations around the Earth-Moon L1 and L2 Lagrangian points. There are five Lagrangian points associated with the Earth-Moon system. The two points nearest the moon are of great interest for lunar exploration.
These points are called L1 (located between the Earth and Moon) and L2 (located on the far side of the Moon from Earth), each about 61,300 km (38,100 miles) above the lunar surface. It takes about 14 to 15 days to complete one revolution about either the L1 or L2 point. These distinctive kidney-shaped orbits are dynamically unstable and require weekly monitoring from ground personnel. Orbit corrections to maintain stability are regularly performed using onboard thrusters.
The ARTEMIS mission implementation and operation represents a joint effort between NASA Goddard Space Flight Center in Greenbelt, Md., the Jet Propulsion Laboratory in Calif., and the University of California, Berkeley, Space Sciences Laboratory.
For details:http://www.nasa.gov/mission_pages/themis/news/artemis-orbit.html
ARTEMIS-P1 is the first spacecraft to navigate to and perform station keeping operations around the Earth-Moon L1 and L2 Lagrangian points. There are five Lagrangian points associated with the Earth-Moon system. The two points nearest the moon are of great interest for lunar exploration.
These points are called L1 (located between the Earth and Moon) and L2 (located on the far side of the Moon from Earth), each about 61,300 km (38,100 miles) above the lunar surface. It takes about 14 to 15 days to complete one revolution about either the L1 or L2 point. These distinctive kidney-shaped orbits are dynamically unstable and require weekly monitoring from ground personnel. Orbit corrections to maintain stability are regularly performed using onboard thrusters.The ARTEMIS mission implementation and operation represents a joint effort between NASA Goddard Space Flight Center in Greenbelt, Md., the Jet Propulsion Laboratory in Calif., and the University of California, Berkeley, Space Sciences Laboratory.
For details:http://www.nasa.gov/mission_pages/themis/news/artemis-orbit.html