GPS in Mid-life with an International Team of Doctors Analyzing IIF-1 Satellite Performance and Backward-Compatibility

With the launch of the first GPS IIF satellite, IIF-1 or SVN 62 on May 27, 2010, the U.S. GPS enters its midlife. The IIF-1 satellite is the very first GPS satellite with an operable L5 payload. The IIF-1 L1 and L2 signals were turned on June 6, 2010, and were set “healthy” on August 27, 2010. The satellite started to transmit L5 signal on June 17, 2010. We formed an international team of doctors. We have been continuously observing the IIF-1 transmission using a variety of facilities since the satellite was launched. This paper shows our examination results of the IIF-1 satellite using our high gain parabolic dish antennas at Stanford USA and at Weilheim, Germany, as well as a global commercial receiver network. Our analyses of the IIF-1 satellite focus on the backward compatibility. In other words, the IIF-1 L1 and L2 signals need to be compatible with other existing satellites of older generation. We conclude that the IIF-1 L1 and L2 signals have a performance similar to other satellites in terms of range accuracy, ephemeris accuracy, signal waveform deformation, and code carrier divergence.