Bottom Line: Don't Worry; Be Happy.
With the possibility of the nation's going to
"Code Red," and the expectation of retaliation, and the expectation
of all sorts of unexpected hostile events' happening in this land,
as the Iraq hostilities gain momentum, we wondered what, if any,
changes we might expect in our GPS system. Specifically, we were
wondering about whether there are plans afoot to once again
reinstate "selective availability," under which civilians operated
until May of 2000. (That system, you may recall, degraded the GPS
system to our sets, resulting in an error margin 10x greater than
the system could produce.)
We
called the FAA, and they told us that, if any contingencies might
be on the table (and they weren't saying there were), they couldn't
talk about them, until such time as the TSA, DoD, or some other
authority wanted them to.
We called a leading GPS manufacturer, and were told there were
no plans, as far as they knew; but they, too, were civilians, and
that they were under the same restrictions we all were, regarding
access to information.
So, we
called the folks who run GPS. Yes, Virginia, there is a whole
agency that does nothing but watch over GPS, and think of things to
make it better. It's called the Interagency GPS Executive Board,
and they are headquartered in the Capital.
We talked with Paula Trimble [no relation] at the IGEB, and she
told us, "US policy has not changed. We do not degrade the global
service from its advertised capability." We know that the system
isn't currently degraded -- that's fairly obvious; what we're
worried about is the possibility that we might be flying a
precision GPS approach, and -- poof! -- we're only within 50~100
yards, instead of the two meters we're accustomed to.
Ms.
Trimble acknowledged that the ability to reinstate SA is a
capability: "Consistent with national policy, the US government
also maintains the capability to prevent the hostile use of GPS and
its augmentation, while maintaining a military advantage in a
theater of operations, without unduly disrupting or degrading
civilian uses outside the theater."
So -- that left us kinda where we started. Ms. Trimble wanted to
give us the best information she was allowed to give, and found one
other official statement: "GPS Selective Availability has not been
used since its use was discontinued May 1, 2000; however, the
ability to deny the enemy regional access to GPS signals in an
engagement does exist, as a military option. It is an option that
would require very high-level policy consideration. If requested by
the Commander of US Forces in the region [in the region of the
conflict --ed]. Because of our national policy, this is not a
decision our government would take lightly."
Would there be any warning, if SA were to be turned on? None of
our experts and contacts would go on the record for this one, but
they all agreed that it would be pretty stupid, tactically, to
announce a degradation in advance.
So, we learned that there are no plans afoot to deny full GPS
capability, except perhaps in an actual war theater; and we found
out that, in order to degrade GPS accuracy, it would take very
high-level involvement (and we reconfirmed that at least some
government decisions are apparently "taken lightly").