Andrew Yee[_1_]
September 28th 06, 10:25 PM
News Service
Cornell University
Ithaca, New York
Media Contact:
Press Relations Office
(607) 255-6074
Sept. 26, 2006
Solar flares cause GPS failures, possibly devastating for jets and distress
calls, Cornell researchers warn
By Thomas Oberst
Strong solar flares cause Global Positioning System (GPS) receivers to fail,
Cornell researchers have discovered. Because solar flares --
larger-than-normal radiation "burps" by the sun -- are generally
unpredictable, such failures could be devastating for "safety-of-life" GPS
operations -- such as navigating passenger jets, stabilizing floating oil
rigs and locating mobile phone distress calls.
"If you're driving to the beach using your car's navigation system, you'll
be OK. If you're on a commercial airplane in zero visibility weather, maybe
not," said Paul Kintner Jr., professor of electrical and computer
engineering at Cornell and head of Cornell's GPS Laboratory.
Alessandro Cerruti, a graduate student working for Kintner, accidentally
discovered the effect on Sept. 7, 2005, while operating a GPS receiver at
Arecibo Observatory in Puerto Rico, one of six Cornell Scintillation Monitor
(SCINTMON) receivers. Cerruti was investigating irregularities in the plasma
of the Earth's ionosphere -- a phenomenon unrelated to solar flares -- when
the flare occurred, causing the receiver's signal to drop significantly.
To be sure of the effect, Cerruti obtained data from other receivers
operated by the Federal Aviation Administration (FAA) and the Brazilian Air
Force. He found that all the receivers had suffered exactly the same
degradation at the exact time of the flare regardless of the manufacturer.
Furthermore, all receivers on the sunlit side of the Earth had been
affected.
Cerruti will report on the findings Sept. 28 at the Institute of Navigation
Meeting in Fort Worth, Texas, where he will receive the best student paper
prize. The full results of the discovery will be published in a forthcoming
issue of the journal Space Weather.
The flare consisted of two events about 40 minutes apart: The first lasted
70 seconds and caused a 40 percent signal drop; the second lasted 15 minutes
and caused a 50 percent drop. But this flare was moderate and short-lived;
in 2011 and 2012, during the next solar maximum, flares are expected to be
10 times as intense and last much longer, causing signal drops of over 90
percent for several hours.
"Soon the FAA will require that every plane have a GPS receiver transmitting
its position to air traffic controllers on the ground," warned Cerruti. "But
suppose one day you are on an aircraft and a solar radio burst occurs.
There's an outage, and the GPS receiver cannot produce a location. ... It's
a nightmare situation. But now that we know the burst's severity, we might
be able to mitigate the problem."
The only solutions, suggested Kintner, are to equip receivers with weak
signal-tracking algorithms or to increase the signal power from the
satellites. Unfortunately, the former requires additional compromises to
receiver design, and the latter requires a new satellite design that neither
exists nor is planned.
"I think the best remedy is to be aware of the problem and operate GPS
systems with the knowledge that they may fail during a solar flare," Kintner
said.
The team was initially confused as to why the flare had caused the signal
loss. Then Kintner recalled that solar flares are accompanied by solar radio
bursts. Because the bursts occur over the same frequency bands at which GPS
satellites transmit, receivers can become confused, leading to a loss of
signal.
Had the solar flare occurred during the night in Puerto Rico or had Cerruti
been operating SCINTMON only at night, he would not have made the discovery.
"We normally do observations only in the tropics and only at night because
that's where and when the most intense ionospheric irregularities occur,"
said Kintner. However, since no one had done it before, Cerruti was looking
at "mid-latitudes" (between the tropics and the poles), where weaker
irregularities can occur both night and day. As a result, SCINTMON detected
the solar flare.
Other authors of the forthcoming paper include D.E. Gary and L.J. Lanzerotti
of the New Jersey Institute of Technology, E.R. de Paula of the Instituto
Nacional de Pesquisas Espaciais and Cornell research associate Hien Vo.
[Thomas Oberst is a science writer intern at the Cornell Chronicle.]
IMAGE CAPTION:
[http://www.news.cornell.edu/stories/Sept06/solar_flares.jpg (113KB)]
Graduate student Alessandro Cerruti, left, and Professor Paul Kintner work
on the antenna on the roof of Phillips Hall. They have found that the kinds
of large solar flares expected in five years or so could produce massive
outages of all GPS receivers on the day side of the Earth. Copyright
Cornell University
Cornell University
Ithaca, New York
Media Contact:
Press Relations Office
(607) 255-6074
Sept. 26, 2006
Solar flares cause GPS failures, possibly devastating for jets and distress
calls, Cornell researchers warn
By Thomas Oberst
Strong solar flares cause Global Positioning System (GPS) receivers to fail,
Cornell researchers have discovered. Because solar flares --
larger-than-normal radiation "burps" by the sun -- are generally
unpredictable, such failures could be devastating for "safety-of-life" GPS
operations -- such as navigating passenger jets, stabilizing floating oil
rigs and locating mobile phone distress calls.
"If you're driving to the beach using your car's navigation system, you'll
be OK. If you're on a commercial airplane in zero visibility weather, maybe
not," said Paul Kintner Jr., professor of electrical and computer
engineering at Cornell and head of Cornell's GPS Laboratory.
Alessandro Cerruti, a graduate student working for Kintner, accidentally
discovered the effect on Sept. 7, 2005, while operating a GPS receiver at
Arecibo Observatory in Puerto Rico, one of six Cornell Scintillation Monitor
(SCINTMON) receivers. Cerruti was investigating irregularities in the plasma
of the Earth's ionosphere -- a phenomenon unrelated to solar flares -- when
the flare occurred, causing the receiver's signal to drop significantly.
To be sure of the effect, Cerruti obtained data from other receivers
operated by the Federal Aviation Administration (FAA) and the Brazilian Air
Force. He found that all the receivers had suffered exactly the same
degradation at the exact time of the flare regardless of the manufacturer.
Furthermore, all receivers on the sunlit side of the Earth had been
affected.
Cerruti will report on the findings Sept. 28 at the Institute of Navigation
Meeting in Fort Worth, Texas, where he will receive the best student paper
prize. The full results of the discovery will be published in a forthcoming
issue of the journal Space Weather.
The flare consisted of two events about 40 minutes apart: The first lasted
70 seconds and caused a 40 percent signal drop; the second lasted 15 minutes
and caused a 50 percent drop. But this flare was moderate and short-lived;
in 2011 and 2012, during the next solar maximum, flares are expected to be
10 times as intense and last much longer, causing signal drops of over 90
percent for several hours.
"Soon the FAA will require that every plane have a GPS receiver transmitting
its position to air traffic controllers on the ground," warned Cerruti. "But
suppose one day you are on an aircraft and a solar radio burst occurs.
There's an outage, and the GPS receiver cannot produce a location. ... It's
a nightmare situation. But now that we know the burst's severity, we might
be able to mitigate the problem."
The only solutions, suggested Kintner, are to equip receivers with weak
signal-tracking algorithms or to increase the signal power from the
satellites. Unfortunately, the former requires additional compromises to
receiver design, and the latter requires a new satellite design that neither
exists nor is planned.
"I think the best remedy is to be aware of the problem and operate GPS
systems with the knowledge that they may fail during a solar flare," Kintner
said.
The team was initially confused as to why the flare had caused the signal
loss. Then Kintner recalled that solar flares are accompanied by solar radio
bursts. Because the bursts occur over the same frequency bands at which GPS
satellites transmit, receivers can become confused, leading to a loss of
signal.
Had the solar flare occurred during the night in Puerto Rico or had Cerruti
been operating SCINTMON only at night, he would not have made the discovery.
"We normally do observations only in the tropics and only at night because
that's where and when the most intense ionospheric irregularities occur,"
said Kintner. However, since no one had done it before, Cerruti was looking
at "mid-latitudes" (between the tropics and the poles), where weaker
irregularities can occur both night and day. As a result, SCINTMON detected
the solar flare.
Other authors of the forthcoming paper include D.E. Gary and L.J. Lanzerotti
of the New Jersey Institute of Technology, E.R. de Paula of the Instituto
Nacional de Pesquisas Espaciais and Cornell research associate Hien Vo.
[Thomas Oberst is a science writer intern at the Cornell Chronicle.]
IMAGE CAPTION:
[http://www.news.cornell.edu/stories/Sept06/solar_flares.jpg (113KB)]
Graduate student Alessandro Cerruti, left, and Professor Paul Kintner work
on the antenna on the roof of Phillips Hall. They have found that the kinds
of large solar flares expected in five years or so could produce massive
outages of all GPS receivers on the day side of the Earth. Copyright
Cornell University