GPS and Air Traffic

Over the past year and particularly over the past 6 months we have heard a great deal about NextGen Air Traffic Control Systems using GPS for guidance.  GPS will allow aircraft to fly more precise routes and permit distances between aircraft to be reduced which should allow more “capacity” into our system.

Increased precision should permit a “redesign” of approaches to airports that will allow aircraft to enter a “pattern” earlier and perform continuous descent approaches that will save fuel and even reduce the workload on pilots.

On flights over oceans, aircraft could use GPS to precisely locate  themselves and then automatically report back their position(s) to traffic control centers which could then “tighten up” routes across those oceans and allow more aircraft to follow an optimal route. 

There is no doubt that GPS is overdue in this game but it isn’t necessarily the “no downside” solution to our problems either. 

GPS signals are provided by satellites and things can happen to those satellites to either block or severely degrade the signals.  Sunspot activity can affect their signals,  for instance.  It’s also not unheard of to suddenly find satellites decommissioned because they were hit by space debris or such intense solar storms.   Suddenly loss of those signals could result in a very intense situation where we find tightly space aircraft without the ability to precisely locate themselves.  The chances for this are, admittedly, statistically very low.  It’s worth an acceptable risk provided aircraft retain guidance redundancy with other systems not dependent on satellites.

Indeed, not all GPS signals are actually emitted from satellites.  There are ground based augmentation systems that permit a finer degree of precision in certain areas.  In fact, one such use is in Instrument Landing Systems being designed for the future.

But there is a security problem with GPS.  First, it is possible to “spoof” GPS signals.  In fact, it’s relatively easy to “spoof” these signals and a reason why the military doesn’t rely completely on GPS signals for guiding munitions and why they’re developing other systems that are not satellite based but which do provide accurate relative navigation.  

Signals by which aircraft would navigate are encrypted but that encryption is somewhat out of date for this era.  While a terrorist wouldn’t necessarily be able to spoof the signal, a foreign country could conceivably do so.  And you can do such “spoofing” by sending a signal from the ground, air or space with equipment that isn’t very costly and not very hard to engineer. 

While aircraft aren’t necessarily going to experience their guidance being impacted by pranksters or terrorists, the risk for it being a target of a foreign nation who decides its at war with the United States or some other country does exist.   Any country capable of doing the math and engineering technology from the 1980′s can potentially engage in this.   That might include countries such as North Korea or Iran.

In addition and quite unfortunately, China has shown its willingness to strike at satellites with missiles.  Again, any country capable of building an intercontinental ballastic missile is now capable of striking at GPS satellites in space.  And don’t think that those won’t be targets in a conflict, they will be.

While we have some safeguards and the United States Air Force works very hard at securing and protecting the existing satellite system, we really need a global commercial navigation system that is secured by a larger, more redundant grid of satellites.  A system that is owned and maintained by responsible nations of the world and one that is designed for air and sea navigation.  A system that is encrypted with modern encryption and upgradeable for the future.   And a system that can be “turned off” selectively for certain regions or countries in times of conflict. 

I’m thrilled we seem to be moving forward with a new generation of navigation systems.  It’s long overdue but I do wish that we would consider the security risks inherent with these systems just a bit more.

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One Response to “GPS and Air Traffic”

  1. Misguided… *So* misguided…

    It has been a long-standing truism in maritime navagation that only a suicidal fool relies solely on one form of navigational aid while at sea. It is even more true and accurate now, in the GPS age. I truly mourn the recent decommisioning of the LORAN-C broadcasting network by the US Coast Guard; although commercial air carriers rarely used LORAN, it was always there if needed, for 68 years. As far as security goes, GPS signals are easly jammed, as they are necessarily weak, relatively speaking. You needed some serious cojones to jam a 4-megawatt LORAN beacon…

    Does anyone still use VLF/Omega for aviation navigation? Is VLF/Omega even active?

    I still can shoot the sun and stars with my sextant, even from 35,000′. Can anyone still do that? Do they even teach people how any more?

    -R
    (gimme an accurate watch, a flat horizon, and a clear sky…)

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