During an Oct. 10 Avionics Magazine webcast, “Navigating the Skies: The Future of GPS,” MITRE CNS Engineering and SpectrumDirector Christopher Hegarty addressed the future of GPS in a more than positive light.

   “There are billions of users of GPS today worldwide and the government is investing tremendous amounts of money in GPS,” Hegarty told Avionics Magazine Editor and Webcast Moderator Emily Feliz. “The GPS constellation has nominally 24 satellites, but we’ve been very fortunate to have an over-populated constellation. There are now 31 healthy satellites in orbit. The system is being modernized to add second, third, and fourth civilian signals, and increase performance. One of the later speakers will go into some of the details on that.”

Lockheed Martin GPS 3 Capability Insertion Program Manager John Frye noted that the GPS system today is really comprised of a constellation of satellites that originally was envisioned to be 24 satellites, which has since evolved to become a system where there’s 34 satellites in orbit.

   “Of those 34, 31 are healthy and contributing to system performance,” said Frye. “And in recent years what they’ve done is expand the constellation design to go from a 24-slot constellation to a 27-slot constellation, providing better geometric performance for the system and better performance for the users. Satellites are contained in six different planes, nominally four satellites per plane, and they are in a orbit altitude where it takes about 12 hours to get around the planet once.”

   CMC Electronics Business Development Manager of Airline Solutions Rex Hygate stressed why the government is making such a hefty investment into issues that impact the way airlines use GPS.

   “The U.S. constellation system is fine,” said Hygate. “But, if the constellation becomes less healthy from the 31 satellites that is now – if it drops below 24, or if there are other unforeseen circumstances – what could happen is that a flight may not end up being cleared, which, for an airline, is, obviously, a very bad thing, and this would be something that they would only find out very shortly before departure. Obviously, passengers would not be pleased with that.”

   Hygate also discussed the upcoming requirements for the U.S. ADS-B mandate, which are stricter than any of the other ADS mandates in the world. “The ADS-B mandate will have an impact, primarily to the airlines. With business aviation and general aviation, they’re updating their avionics, their GPS receivers, already, so, for them, the problem is not as pressing, but they’re not immune,” said Hygate. “The trouble for the 2020 mandate is that when all aircraft operating in the United States have to able to meet it, the satellite constellations will not yet be complete. They could barely be complete by 2020. The ground infrastructure is still not entirely complete and the cert standards, as Christopher mentioned, are not complete yet. Some of them haven’t even started.”

   To date, all GPS satellites have been launched from Cape Canaveral. Frye said that due to the process of mergers and acquisitions, the United States is at a point now where there are two contractors responsible for all the satellites that are currently in orbit or are soon to be built. Boeing built the Block 2 and 2A satellites and is currently in the process of deploying all of the Block 2F satellites, one of which launched earlier in October. Lockheed Martin was contracted for the 2R and 2R-M satellites, which are all deployed, allowing the company to focus on its GPS 3 program, with a planned launch of the first GPS satellite in the 2014 to 2015 timeframe.

   “What we’re looking to provide to the users is a combination of things [with GPS-3],” said Frye. “First, is improved position navigation and timing accuracy, and the other is to provide higher power signals for both civil and war fighter applications. In addition, we’ve got a fourth civil signal, the L1C signal and an enhanced M-code Earth coverage power level, which is a benefit to the warfighter in the future when the M-code user equipment is made available.”

   An important element of the Air Force’s GPS program, according to Frye, was that it that called out for a “graceful” growth path. “They wanted a satellite platform that would allow them to add capability over time and not have them locked out from adding new features within a timeframe of a decade or so,” said Frye. “This has been a problem with past platforms. But overall, the objectives of the program are to deliver this high-confidence acquisition and avoid previous space program acquisition problems. The Air Force has done a terrific job at maintaining a very solid requirements baseline for the program that has not changed at all since the program began back in May 2008. So, having that solid requirements baseline has been critical to not having schedule problems or cost overruns.”

   When asked which GPS 3 technology presented the biggest challenges for Lockheed Martin, Frye admitted that a lot of the technology for GPS 3 is derived from the GPS 2R and 2R-M spacecraft. “I think that one of the things that we need to keep an eye is clock technology. The supplier of the clocks for the 2F and the GPS 3 satellites was PerkinElmer, and now it’s been bought up by and operated by Excelitas,” said Frye. “Those are really at the heart of the navigation payload, and so ensuring that that technology is in place and available is important. One of the things we’re doing with the GPS 3 program is with the government’s funds developing a second source of atomic clocks to make sure we’ve got two domestic sources of very high precision atomic clocks to be used in space.”

   The webcast panelists also discussed the biggest challenges and threats to the overall GPS system. Hegarty said the buzz coming from most GPS industry conferences and meetings revolves around intentional and unintentional jamming.

   “GPS jammers are available over the Internet. They’re illegal to use and I know that the U.S. Department of Homeland Security is struggling quite a bit to sort out how to manage through all that,” said Hegarty. “Aside from situations where you’ve got intentional military jamming in contested areas, there have been recent examples in airports, such as in North Jersey, where a truck driver is driving with a GPS jammer because he doesn’t want the home office being able to keep track of where his truck was. The jammer was broadcasting a high-enough level that actually was interfering with airport operations.”

   National Air Transportation Association President Tom Hendrickswas asked for his perspective on the controversial LightSquared proposal, which drew the ire of the GPS industry last year over interference issues. He said that though studies continue on the LightSquared interference issues, the facts that drove the FCC to decline its license to operator had not chanced.

   “The RTCA did a very in-depth analysis,” said Hendricks. “There’s been continued study. In fact, their Special Committee 159 I understand just met recently again to look at this issue. For the aviation community, it is not necessarily about LightSquared – it is about how fragile that signal is. LightSquared is continuing to try to advocate for solutions to allow them to recoup their investment. And, again, for the community, it has been about protecting this spectrum that’s so crucial to all of us out there. One of the key issues for us in the operational world out there, is the tremendous improvement in safety GPS has allowed us to utilize. I’ve flown into Quito, Ecuador, and Guatemala City in 757s in my previous career and I can tell you that having GPS on board the aircraft fundamentally altered how we fly into those environments, giving us better reliability, much more precise positioning over the ground in very challenging terrain environments, and knowing that we had our enhanced ground proximity warning system that had a very accurate location and compared that against terrain maps on board the aircraft. It just revolutionized airline traffic.”