This might be a dumb question, but I've never been very good with orbital mechanics.
Here goes: how do I get an object to orbit the moon synchronously?
Fleegle
lunar synchronous orbit
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Matt McIrvin
- Posts: 312
- Joined: 04.03.2002
- With us: 22 years 6 months
Lagrange points
Stay where you are. You're IN lunar synchronous orbit-- or as close as anything gets. (You only see one face of the Moon, after all.)
Since the Moon rotates synchronously with its revolution around the Earth, and the Earth itself dominates orbital dynamics in the system, the closest we can come to being in synchronous orbit around the Moon is to be on Earth itself, or at one of five special spots in the Earth-Moon system called Lagrange points.
Of the five, the two in which an object can orbit stably are L4 and L5, which are the two points that form an equilateral triangle with the Earth and Moon, in the Moon's orbital plane. They are sometimes mentioned as potential locations for space colonies.
The other three are three special spots along the Earth-Moon line: L1, L2, and L3. L1 is between the Earth and Moon, L2 is behind the Moon, and L3 is behind the Earth, opposite the Moon. At these spots the equilibrium is unstable, so a spacecraft would have to expend some fuel to keep from drifting off position.
The Sun-Earth system has the same set of Lagrange points; of course, these wouldn't be "synchronous orbits" with respect to Earth since the Earth's rotation isn't tidally locked to the Sun. The SOHO solar observatory is at the Sun-Earth L1, and the MAP cosmic background radiation probe is at Sun-Earth L2 (actually, they move around these points in "halo orbits").
There are some asteroids in the Sun-Jupiter L4 and L5 positions, called the Trojans. Some moons of Saturn have little co-orbital moons at the moon-Saturn L4 or L5 point.
Since the Moon rotates synchronously with its revolution around the Earth, and the Earth itself dominates orbital dynamics in the system, the closest we can come to being in synchronous orbit around the Moon is to be on Earth itself, or at one of five special spots in the Earth-Moon system called Lagrange points.
Of the five, the two in which an object can orbit stably are L4 and L5, which are the two points that form an equilateral triangle with the Earth and Moon, in the Moon's orbital plane. They are sometimes mentioned as potential locations for space colonies.
The other three are three special spots along the Earth-Moon line: L1, L2, and L3. L1 is between the Earth and Moon, L2 is behind the Moon, and L3 is behind the Earth, opposite the Moon. At these spots the equilibrium is unstable, so a spacecraft would have to expend some fuel to keep from drifting off position.
The Sun-Earth system has the same set of Lagrange points; of course, these wouldn't be "synchronous orbits" with respect to Earth since the Earth's rotation isn't tidally locked to the Sun. The SOHO solar observatory is at the Sun-Earth L1, and the MAP cosmic background radiation probe is at Sun-Earth L2 (actually, they move around these points in "halo orbits").
There are some asteroids in the Sun-Jupiter L4 and L5 positions, called the Trojans. Some moons of Saturn have little co-orbital moons at the moon-Saturn L4 or L5 point.