Is a Halo Orbit, such as the one employed by the SOHO spacecraft, a powered orbit (requires corrective burns)?. L1 is unstable, but everything I Google about Halo Orbits seem to suggest that the spacecraft happily orbits the L1 point in a Halo Orbit without corrective burns. Does it do this naturally, or is it a consequence of the correction burns that must be made to keep it from drifting from the L1 position? How about Lissajous Orbits? Are they powered?