Questions for the gurus...

[scooter]

I've got a couple of questions here, seeing as we have some folks present who do "space" on a daily basis.
A while back, in one of the threads, the idea of a "luna-stationary" orbit popped up. I got to thinking (and fiddling with it in Orbiter) and it is an interesting challenge, As I got farther from the Moon, the gravitational influence decreased significantly, as the relative influence of Earth and Sun increased. About 30-some thousand km lunar radius, it started to become a situation of a rotating argument of perilune at roughly my "groundspeed". I didn't follow through for an entire orbit, but the lunar pull seemed to be "losing". So, with all three bodies in play, is such an orbit possible? Or is that where the Lagrange points come into play?
Also, I can routinely get to geostationary with less than 5m/s groundspeed and inclination <.005 degrees from the equator. For real world satellites, what are the normal deviations for stationkeeping? I know that this sim doesn't have to contend with solar activities and gravitational deviations that keep real world sat drivers busy.

Love this sim, just wondering how close it is to the real thing.

Dave

[gwiz]

Well, I can answer half the question. Typical geostationary drift rates are around 0.01 degrees per day, inclinations about 0.05 degrees.

[tofu]

scooter said:

A while back, in one of the threads, the idea of a "luna-stationary" orbit popped up.

The only way to do a luna-stationary orbit (as far as I know) is to position the satellite in L1, L2, L4, or L5. Supposedly, it is possible to do this in Orbiter. I bet if you ask on the forums, someone would even write an MFD to help find the lagrange points.

www.freemars.org/l5/aboutl5.html

[gwiz]

Considering geostationary orbits, I think the reason why real satellites do much better than your sim in longitude but worse in latitude is that the gravitational perturbations are a lot higher for latitude. There have been quite a few cases where a satellite running low on propellant has been allowed to drift in latitude, so that the daily earth track ends up as a very thin figure of 8 spanning maybe 20 degrees or more in latitude. In longitude, there are a couple of positions which are actually stable. A slowly drifting satellite will oscillate about one of these points. I can't recall the actual figure, but I believe the oscillation period is of the order of months.