CGSIC Bulletin: Public Release of GPS IIR and IIR-M antenna patterns

Partnering with the U.S. Coast Guard Navigation Center (NAVCEN), U.S. Space Force and Lockheed Martin Space have released the GPS IIR/IIR-M satellite antenna patterns for world-wide public use. Additionally, the Institute of Navigation has offered a related ION Journal article free to the public to accompany the antenna patterns.

The files include:
GPS Block IIR and IIR-M Broadcast L-Band Antenna Panel: Its Pattern and Performance (Journal of Navigation paper)
The GPS Block IIR/IIR-M Antenna Panel Pattern (presentation)
Appendix A — IIR and IIR-M SV-Specific Antenna Panel Patterns – Plots
Appendix B — IIR and IIR-M SV-Specific Antenna Panel Patterns – Data
Appendix C — IIR and IIR-M SV-Specific Antenna Panel Patterns – Phase Data

The Global Positioning System (GPS) Block II Replenishment (IIR) space vehicle (SV) began improving upon its baseline design in 2003 with the launch of the first Block IIR SV retrofitted with a redesigned ‘improved’ antenna panel. This is the Earth-facing panel providing the GPS L-band broadcast signal. The improved antenna panel includes redesigned L-band elements mounted on the SV Earth-facing structure in the same manner as the original ‘legacy’ antenna panel.

The use of GPS signals for spacecraft navigation has increased in general over the last few decades and navigation employing GPS observations for spacecraft in low-Earth orbit is now considered routine. However, the situation is quite different for spacecraft that fly in the Space Service Volume above the GPS constellation, including MEO, GEO, HEO, and missions to the Moon and beyond. For these spacecraft, reception of GPS transmit antenna side lobe signals is essential to improve availability and performance of on-board navigation and timing. In this context, the knowledge of the full antenna pattern (main lobe and side lobes) from the transmitting antennas of each of the GPS satellites is essential.

These published antenna patterns and associated Institute of Navigation citation describe both IIR and IIR-M antenna panel versions, their broadcast signal patterns, the performance observed in factory testing, and their on-orbit performance.