If a somewhat bizarre chain of events unfolds, as it is expected to do, both the Federal Aviation Administration (FAA) and U.S. Department of State could find themselves in the embarrassing position of having to accept the use of a foreign-controlled navigation system to guide aircraft landing at U.S. airports.
The chain starts with word from Washington officials that the space-related budget of the Department of Defense (DoD) is under severe strain due to massive overspending on security initiatives, notably the Space Based Infra-Red System (SBIRS) anti-missile shield. As a result, DoD has been scrutinizing all of its other space programs, and siphoning off funds from ones with lower priority. The planned GPS III is one such program.
Currently in a competitive design phase at Boeing, Lockheed Martin and Spectrum Astro, GPS III would gradually replace the current GPS satellites in orbit with more advanced, higher-power units. Launch of the first GPS III satellite would be around 2008, with a full, 24- to 30-satellite constellation forecast to be in place between 2013 and 2015. While heavily military oriented, these new satellites would carry an important civil aviation capability–the so-called third civil frequency, known as L5. (They would also carry a second civil frequency, L2, but this is not certified for aviation use.)
L5 is important because airborne GPS receivers could use it in conjunction with the present L1 civil frequency to virtually eliminate the position errors produced by random and unpredictable ionospheric activity. This activity prevents GPS from providing the accuracy required for low-visibility Category I landing approaches.
The FAA would use this capability, in conjunction with its Wide Area Augmentation System (WAAS), to provide nationwide precision landing guidance at virtually every airport. This would not only greatly enhance safety, but would allow FAA to garner major cost savings by decommissioning a large number of the more than 1,000 instrument landing systems (ILS) across the country.
However, it turns out that the present, single-frequency GPS satellites are exceeding their expected orbital "lives" by substantial margins, thereby making their replacement by GPS III units a much lower DoD priority. DoD insiders also say that the next-generation satellites could cost up to three times as much as current units.
Inevitably, these two factors attracted the attention of DoD budget cutters, with the result that the first GPS III launch may not occur before 2015 at the earliest, with the full constellation in orbit around 2022, or later. And, while it is possible that some of the present-generation satellites being held as replacements for failed orbiting units could be upgraded to offer L5 transmissions between now and 2015, a full, L5-capable constellation must be in place for reliable landing guidance.
Now, the embarrassing part. Through the State Department, the United States has offered the world’s nations full and free use of GPS for any applications they wish, including future Cat I landing guidance. Some countries raise concerns about the system’s foreign ownership and control, but the State Department has chided them for their xenophobic views towards American generosity. And no one at the State Department could have imagined that they would subsequently steal a march on us.
But by 2008, Europe expects to have a complete, GPS-like, Galileo navigation satellite constellation in orbit around the Earth. Galileo is designed to be totally compatible with GPS. Essentially, airborne receivers won’t be able to tell the difference between the signals from either system. Except that Galileo’s satellites would be transmitting the L1 and L5 frequencies necessary to support Cat I landings almost 15 years ahead of the United States.
There’s no question that nations around the world will quickly use this capability to increase domestic aviation safety and save money, just as FAA had planned. But there are other, more interesting, questions. Would FAA approve the use of a foreign-owned and -controlled satellite system to land aircraft in the United States? Or would the State Department–which has strenuously opposed Europe’s plan to build Galileo from the outset, on the basis that GPS would do everything satnav users could possibly want–now refuse to allow its use in the United States, precisely because of its foreign ownership and control? And if so, would U.S. pilots be content to see satnav Cat I operations approved in every country around the globe, except the United States? How this potential twist of events progesses, we can only wait and see.
William Reynish is a regular contributor to Avionics Magazine.