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Astrodynamics is a core discipline within space-mission design and control. Celestial mechanics treats more broadly the orbital dynamics of systems under the influence of gravity, including both spacecraft and natural astronomical bodies such as star systems, planets, moons, and comets.
A halo orbit is a periodic, non-planar orbit associated with one of the L 1, L 2 or L 3 Lagrange points in the three-body problem of orbital mechanics.Although a Lagrange point is just a point in empty space, its peculiar characteristic is that it can be orbited by a Lissajous orbit or by a halo orbit.
In contrast with low lunar orbit which NASA characterizes as being deep in the lunar gravity well, NRHO is described as being "balanced on the edge" of the gravity well. [2] The NRHOs are a subset of the L 1 and L 2 halo families. [3] This orbit type could also be used with other bodies in the Solar System and beyond.
In this case, non-inclined orbits are called equatorial. [2] For a heliocentric orbit, the ecliptic or invariable plane. In this case, non-inclined orbits are called ecliptic. [2] For an orbit outside the Solar System, the plane through the primary perpendicular to a line through the observer and the primary (called the plane of the sky). [3]
When plotted, they form a tube with the orbit about the Lagrange point at one end. The derivation of these paths traces back to mathematicians Charles C. Conley and Richard P. McGehee in 1968. [4] Hiten, Japan's first lunar probe, was moved into lunar orbit using similar insight into the nature of paths between the Earth and the Moon.
For example, there are five of these points in the Sun-Earth system, five in the Earth-Moon system, and so on. Spacecraft may orbit around these points with a minimum of propellant required for station-keeping purposes. Two orbits that have been used for such purposes include halo and Lissajous orbits. [5]
The top of the third tank being so near the roof posed challenges for inserting large test hardware. Final preparations for testing took several more months. Engineers elected to fill the tank slowly to be able to repair any leaks found along the way, and they filled it, finding and fixing a few leaks, between February 29 and March 11, 1968.
The James Webb Space Telescope (JWST) is in a libration point orbit around the L2 Lagrange point of the Sun, and Earth-Moon barycenters. [ 2 ] [ 3 ] Because libration point orbits are quasiperiodic, the telescope must make frequent small burns to maintain proximity to the L2 point, as part of orbital station keeping , limiting the lifespan of ...