Halo-Orbit

A halo orbit is a periodic orbit around a Lagrange point of unstable L1 to L3 in a three- chamber system. Here, the Lagrange point in an orbit is mostly encircled outside the orbital plane, the orbits are not coplanar so. So that the object during the time describes many slightly different orbits around the central Lagrange point. This sphere, ie the halo, gives this orbit its name. Since this path but is not stable, regular correction maneuvers are required. In contrast to a Lissajousorbit the web is thereby approximately periodically.

To the stable Lagrange points L4 and L5 objects can also remain completely without drive in a halo or Lissajousorbit.

The name goes back to the thesis of Robert W. Farquhar in 1968. Farquhar suggested to place a relay satellite in the L2 point of the Sun-Earth system to allow in this way with the Apollo spacecraft on the side of the moon radio contact. These plans, however, were not implemented.

The first mission on a halo orbit was launched in 1978 ISEE - third In the 1980's showed Kathleen Howell, a professor at Purdue University in Indiana, USA, that the analytical considerations Farquhar were numerically improved. Used Subsequently, numerous other missions such as the solar observatory SOHO ( to L1), Genesis ( also to L1), as well as the missions Herschel and Planck (both to L2, 2009) halo orbits.