The Iridium constellation is being replaced by new satellites. There are six planes with 11 satellites + one spare each. Since the Falcon 9 launcher can only carry ten satellites per launch, filling the planes is not an easy task. Out of the first launch, eight satellites were inserted into orbit to take the slots of the old satellites. Two vehicles have started drifting to the next plane (westwards). It will take them app. 10 months to get there.
The next launch will insert only five satellites into service orbit, another five will be drifted west- as well as eastwards.
I would like to know how the drifting is actually handled. I somewhere read that as far as I understood, westward drifts are helped by precession. I figured out that the drifting satellites move app. 0.11 degrees more to the west than their non-drifting companions' RAAN changes on a daily basis. The drifters are in a lower 629/611 vs. 783/781) and more excentric orbit (0.0013000 vs 0.0002100 acc TLEs) and have a slightly lesser inclination (85.88 vs 86.4). Do I correctly assume that these factors aid the drift? And apart from that, do the vehicles do side-burns on a continuous basis? And if so, does this require less delta v than - hypothetically speaking - putting them in an equatorial orbit and spitting them out at the appropriate RAAN to make a (nearly) right-angle turn (I know it could not work like this, but just to have a simplified model for my brain)?
I guess it also needs to be kept in mind that the drifting satellites have to end up in very precise positions, since they have to perfectly fit into the slots of the constellation. They have to cross-link with the satellites before and behind them as well as to the ones in the planes east and west.
Anything else that comes into play that I haven't even touched upon?