In this question someone mentioned the idea of a Statite, a satellite which is stationary above a planet without being in orbit, usually in an orientation which is not possible with an orbit. It seems for obvious reasons that this could be particularly useful for observation of a region which isn't along the rotational path of the planet (can't use GSO to maintain line of sight) such as the poles.
Apparently this form of satellite was patented by Robert L. Forward but mentions of the feasibility of this type of satellite and whether or not anyone has seriously considered using one were omitted in many sources I've found.
Note: Lagrange orbits are technically a statite orbit, but they use another body to balance out the gravity. I'm talking about a statite which actively fights gravity, not one at an equilibrium point.
Usually a statite seems to do the following:
- Uses a method of propulsion that is "infinite"/sustainable (such as solar sails).
- Hovers in a single location above a body, maintaining the distance (but not necessarily attitude) with a near zero velocity relative to that body.
I suppose my overall questions would be:
- Is this form of satellite purely hypothetical?
- Can anyone find any mission proposals for a statite-like mission?
- Is it proven mathematically to be possible/stable for extended periods of time?
- If it is, are there specifics? How big would this crazy device need to be?
Note: I specifically mention Polar statite because that's the only application I can think of, if there is a proposal for a non-polar statite or something else, feel free to share that as well.