Inside GNSS reports an interesting news about Iridium and GPS. Iridium is the commercial satellite constellation developed by Motorola and launched in 1998. It has 66 LEO satellites. Iridium can help GPS performances, like Inside GNSS says: " Awarded by the U.S. Navy’s Naval Research Laboratory (NRL), the funding will be used for research, development, and demonstration of the High Integrity GPS Technology Concept — known more commonly as iGPS. The program is developing techniques that enable faster acquisition (time to first fix or TTFF) of GPS satellite signals in adverse operating environments, including those with RF interference or urban settings. The i-GPS architecture involves high-precision time transfer of GPS time and its rebroadcast over the higher powered Iridium communications channels".