These two also bring us up to 12 L2C capable birds (plus maybe SVN49 if they ever figure out a workable fix). Anyone know what the minimum constellation is before it goes operational? 18? 24?
In satellite navigation parlance, L1 and L2 refer to GPS radio frequency bands where the navigation signals are transmitted. Older satellites transmit the 'legacy' signals while the newer ones transmit 'legacy' plus 'modernized' signals.
L2C is a modernized civil signal that has never been enabled to send navigation messages. There's a nice article about L2C modernization at GPS World Magazine.http://www.gpsworld.com/2c-or-not-2c/
The system operators cite the inability of the current ground infrastructure to operate L2C as the reason for not setting the signal usable for navigation. That includes world wide network of remote monitoring stations and the master control station at Schriever Air Force Base, Colorado.
There's a contract in place, that hasn't been free of controversy, to develop a master control station called the OCX that will support the complete suite of legacy and modernized signals. OCX is tightly coupled with the arrival of Block III satellites and probably will not be delivered before 2016.
Apparently, it's not just a matter of the number of available modernized satellites that will determine when the new signals are usable for navigation. Meanwhile, those who argue the signal is useful now and should be available from the capable satellites will remain frustrated.