GPS World: Forthcoming Solar Cycle Could Disrupt GPS, Communications

NOAA: Forthcoming Solar Cycle Could Disrupt GPS, Communications
http://uc.gpsworld.com/gpsuc/content/printContentPopup.jsp?id=483210


Jan 9, 2008
GPS World

A new 11-year cycle of heightened solar activity, bringing with it
increased risks for military and civilian communications, including
GPS signals, showed signs it was on it its way with the appearance of
the cycle's first sunspot, NOAA scientists said last week.

The sunspot appeared in the sun's Northern Hemisphere, according to
the U.S. National Oceanic and Atmospheric Administration (NOAA).
"This sunspot is like the first robin of spring," said solar
physicist Douglas Biesecker of Nova's Space Weather Prediction
Center. "In this case, it's an early omen of solar storms that will
gradually increase over the next few years."

A sunspot is an area of highly organized magnetic activity on the
surface of the sun. The new 11-year cycle, called solar cycle 24, is
expected to build gradually, with the number of sunspots and solar
storms reaching a maximum by 2011 or 2012, though devastating storms
can occur at any time, according to NOAA.

During a solar storm, highly charged material ejected from the sun
may head toward Earth, where it can bring down power grids, disrupt
critical communications, and threaten astronauts with harmful
radiation. Storms can also knock out commercial communications
satellites and swamp GPS signals. Routine activities such as talking
on a cell phone or getting money from an ATM could suddenly halt over
a large part of the globe, NOAA warned.

"Our growing dependence on highly sophisticated, space-based
technologies means we are far more vulnerable to space weather today
than in the past," said Vice Admiral Conrad C. Schoolteacher, Jr.,
undersecretary of commerce for oceans and atmosphere and NOAA
administrator. "[NOAA's] space weather monitoring and forecasts are
critical for the nation's ability to function smoothly during solar
disturbances."

Last April, in coordination with an international panel of solar
experts, NOAA issued a forecast that solar cycle 24 would start in
March 2008, plus or minus six months. The panel was evenly split
between those predicting a strong or weak cycle. Both camps agree
that the sooner the new cycle takes over the waning previous cycle,
the more likely that it will be a strong season with many sunspots
and major storms, said Biesecker. Many more sunspots with solar cycle
24 traits must emerge before scientists consider the new cycle
dominant, with the potential for more frequent storms, NOAA said.

The new sunspot, identified as #10,981, is the latest visible spot to
appear since NOAA began numbering them on January 5, 1972. Its
high-latitude location at 27 degrees North, and its negative polarity
leading to the right in the Northern Hemisphere are clear-cut signs
of a new solar cycle, according to NOAA experts. The first active
regions and sunspots of a new solar cycle can emerge at high
latitudes while those from the previous cycle continue to form closer
to the equator.

"Communication is the problem to the answer."

Sam Wormley schrieb:


Hello,

doea anybody remember to GPS problems in 2000 or 2001 caused by solar
storms?

Bye

Uwe Hercksen wrote:



Abstract from ION GNSS 2006 (Sept. 26-29)

Observed GPS and WAAS Signal-to-Noise Degradation Due to Solar Radio Bursts
A. Cerruti, Cornell University

GPS signals, systems, and navigation accuracy are vulnerable to a
variety of space weather effects that are caused mostly by the
ionosphere. However, the sun, which is sometimes a strong radio source,
is the cause of GPS signal interference presented here. The first
direct observations of GPS L1 (1.57542 GHz) signal-to-noise ratio
degradation on two different models of GPS receivers due to the solar
radio burst associated with the 7 September 2005 solar flare are
presented.

Signal-to-noise ratio data from three identical, collocated receivers
at Arecibo Observatory and also from four identical receivers of a
different model located in Brazil, were available at the time of the
solar radio burst. These receivers were all in the sun-lit hemisphere
and all were affected similarly. The maximum solar radio burst power
associated with the 7 September 2005 flare had a peak intensity of
about 8,700 solar flux units (1 SFU = 10-22 W/m2-Hz) RHCP at 1,600 MHz,
which caused a corresponding decrease in the signal-to-noise ratio of
about 2.3 dB across all visible satellites. Only the right-hand,
circularly polarized (RHCP) emissions affected the GPS signals.

To confirm the effect, the solar radio burst associated with the 28
October 2003 flare was investigated. Although polarization data were
not available for this event, the maximum degradation at GPS L1 was
about 3.0 dB, and a degradation of 10 dB was observed on the
semi-codeless L2 signal for a solar radio burst of 13,600 SFU.

The event analyzed herein can be used to scale historical solar radio
bursts of 80,000 SFU. Decreases of 12 dB (21 dB) in the L1 (L2,
semi-codeless) signal-to-noise ratio are implied along with loss of
tracking for inadequately designed GPS receivers. Since solar radio
bursts affect all satellites in view of a receiver, all receivers in
the sun-lit hemisphere, the new Galileo navigation system, and all
space-based augmentation systems such as WAAS and EGNOS, they are a
potential threat to life-critical systems.

s
s
s

Hmmm, Sam, does this mean that we should defer any military
engagements until the next sunspot cycle is over, since many if not
most of the military's "smart weapons" like Tomahawk now employ GPS
based guidance to achieve their pinpont accuracy? :-)

Harry C.