Why launch window for launch to GEO?

[Nibb31]

Launchers don't typically launch the satellites to GEO directly. Usually, the upper stage puts the satellite into GTO (geostationary transfer orbit), which is an orbit with an apogee at GSO altitude and a low perigee, and is discarded. That is where the launcher's responsibility ends and the satellite operator takes over.

However, they don't go straight from GTO to GEO in one go. They typically orbit in GTO a couple of times while systems are checked out and deployed. Also, satellites are usually equipped with small thrusters (their main purpose is station keeping), so the satellite has to raise its perigee over multiple apogee burns. This means that it might take a dozen of GTO orbits to actually reach GEO.

Of course, each of these burns are carefully planned, and with the final burn circularizing the satellite in the target longitude position. The number of GTO orbits, the apogee manoeuvers, as well as sun exposure and battery life, determine the launch window.

Edited October 18, 2014 by Nibb31

[Kerbart]

If only there were some kind of software that would allow you to simulate putting a satellite into orbit so you could find out if there were any efficiencies to be gained by picking a specific launch window in order to get a specific position for geostationary orbit!

[Tommygun]

If only there were some kind of software that would allow you to simulate putting a satellite into orbit so you could find out if there were any efficiencies to be gained by picking a specific launch window in order to get a specific position for geostationary orbit!

.....MechNasa?