By Paul Crampton, Spirent Federal
Paul Crampton
As we bid farewell to the last GPS-IIA satellite and read of delays to both the launch schedule for GPS III satellites and roll-out of the OCX program, we are mindful of the need to maintain GPS as the “Gold Standard” in GNSS.
Certainly, new signals, enhanced resilience and expanded capabilities are offered by the modernized GPS playbook. Delays relative to both the BeiDou and Galileo constellations could seriously impact the position of GPS on the medals podium — maybe not in the longer term, but certainly in the coming few years.
This may have a secondary impact on the receiver market, shifting focus away from GPS to more capable signals in the near term. Once GPS has caught up, receiver manufacturers may choose to retain the technology that they developed to capitalize on BeiDou and Galileo signals, rather than developing their legacy GPS capabilities.
GPS L2C is currently “pre-operational,” transmitted by slightly more than half the existing mixed-generation satellite fleet and waiting for OCX support. As of Feb. 20, a realistic estimate for operational capability of GPS L2C is now 2023.
GPS L5 is also pre-operational, transmitted by slightly less than half of the GPS satellites and waiting for OCX support. As of Feb. 20, a realistic estimate for GPS L5 is 2027.
The forecast for GPS L1C operational capability is the late 2020s. This is intended to be the signal that offers international interoperability with the current interoperability signals offered by existing BeiDou and Galileo satellites.
Delays to the implementation of GPS L1C may mean that GPS misses the interoperability boat entirely. During the delay, new interoperability capability with even more robust signals could be devised and lofted aboard Galileo, BeiDou and GLONASS satellites. By then, other countries could also develop their own constellations, possibly regional or even global systems.
Potentially, GPS could be left behind as other nations discuss non-GPS internationally interoperable signals on yet-to-be launched satellites. This may have a profound impact on SBAS, too. Differential corrections provided by the Japanese MSAS, Russian SDCM and European EGNOS SBAS systems might evolve to support “beyond L1C” interoperability signals. Aircraft landings at world airports could mandate the use of corrections to these new signals. This might mean that U.S. receiver manufacturers could be frozen out, or will have to incorporate these new interoperable signal standards.
GPS Block III satellites along with OCX offer improved signals, capabilities and resilience, but the satellites need to be flying, OCX needs to be operational and receivers need to be in the hands of the users. Sooner rather than later is a must for Gold-Standard GPS.
Paul Crampton is a senior systems engineer at Spirent Federal Systems with more than 30 years of GPS experience.