Lunar Orbit
Written by Fraser Cain
Earthrise Apollo 8. Image Credit: Bill Anders, NASA
When a spacecraft is orbiting around the Moon, we call this lunar orbit. Many spacecraft have been sent to explore the Moon, and once they're orbiting around and around in a stable orbit, they're in lunar orbit. It's important that you don't confuse this with the orbit of the Moon, which is the Moon's journey around the Earth. Lunar orbit is when objects orbit the Moon.
The first spacecraft sent into lunar orbit was the Soviet spacecraft Luna 1, on January 4, 1959, which passed within 5,995 km of the Moon's surface. Another spacecraft, Luna 3, made a figure-8 trajectory around the Moon in October, 1959, and became the first spacecraft to image the far side of the Moon.
The first spacecraft that actually orbited the Moon was the Soviet Luna 10. It arrived at the Moon in April, 1966, and remained there until May 30, 1966. After that, several US satellites were sent into lunar orbit. During the Apollo manned space missions, the Command and Service Module remained in lunar orbit while the landers detached and landed on the surface of the Moon. The module orbited at an altitude of 100 km, taking about 2 hours to complete an orbit around the Moon.
Maintaining a stable orbit around the Moon is actually quite difficult. there are large regions of higher gravity which pull at spacecraft as they fly overhead. Once a spacecraft gets below 100 km altitude above the surface of the Moon, it can only last a few months before the gravity pulls into a crash landing.
Were you looking for an article about the orbit of the Moon? That's a completely different topic.
Here's an article from NASA about how hard it is to orbit the Moon.
You can listen to a very interesting podcast about the formation of the Moon from Astronomy Cast, Episode 17: Where Did the Moon Come From?
Filed under: Astronomy
