The Coast Guard supplies knowledge on the part middle of the GPS III antenna
Lockheed Martin Space has released the factory-measured data for the phase center of the GPS-III satellite antenna, as well as the data for group delay and intermediate signal correction for SVN-76 and SVN-77, the US Coast Guard’s Civil GPS shared with Service Interface Committee (CGSIC).
The information can be found on the US Coast Guard Navigation Center website under the IIR / IIR-M antenna pattern data files.
The phase center and inter-signal bias data included in this new version provide additional information that supplements the previously available antenna gain pattern data.
Note that the GPS III satellite vehicles (SVNs) also send the Inter-Signal Corrections (ISCs) in the various LNAV / CNAV messages according to all external IS / ICDs. The value sent by the constellation in orbit is not the factory-measured ISCs, but rather the ISCs estimated by the Stanford Research Institute (SRI) in orbit.