GPS Satellite constellation to be increased from 24 to 27.

The enlarged constellation of satellites was just announced by US Air Force. It will take about 24 months to move the existing satellites to provide improved accuracy from the larger constellation as well as improved availability of the signals in mountainous terrain. Today there are 30 operative satellites in orbit with six acting as backups. No new satellites need to be launched to expand the existing system as they are already in orbit.