Is the sky really falling or is Chicken Little snowing us?
We’ve recently heard reports that GPS satellites are in jeopardy of failing. It’s been on television, radio, newspapers and of course the internet.
As a result, I’ve heard many questions and concerns from current and potential GPS users about the facts and ramifications of this scenario. So, I researched what’s really going on and how it might affect GPS users.
A GPS satellite has an average life of 7.5 years, which means they must constantly be replaced. Boeing has been the primary contractor for most of the American GPS satellites.
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In about 2005, it was decided to modernize the technology in all future GPS satellites. The new Block IIF satellites are built with expandability to accommodate new upgrades or evolving requirements.
Also, the new satellites will offer another civilian signal called L5. Until now, GPS frequencies have been L1, L2, L3 and L4. The L1 frequency is designated for civilian use with L2 shared by civilians and military. The L3 and L4 frequencies are designated solely for military use. L5 is good news for civilians.
It will take a few years for Boeing to build and launch 12 Block IIF satellites to get the L5 signal operational. The first one had been scheduled for launch in 2007. However, contractor issues and high personnel turnover delayed the scheduled launch to November 2009.
“It is uncertain whether the Air Force will be able to acquire new satellites in time to maintain current GPS service without interruption,” the U.S. Government Accountability Office (GAO) said in a May 7 report it was asked to write on the modernization of GPS.
“If not, some military operations and some civilian users could be adversely affected.”
With that said, the satellites are not falling out of the sky or shutting off. More than 30 functioning satellites are in U.S. GPS orbit. We need only 24 of them to maintain GPS at its current level of precision. The GAO said there is a 95 percent chance 24 satellites can be maintained.
“Going below 24 (satellites) won’t happen,” said col. Dave Buckham, the Air Force Space Command’s lead for position, navigation and timing.
The command is implementing plans and procedures to diminish the risk and prevent any degradation in GPS performance.
Back-up options exist if the performance of U.S. GPS does somehow degrade. The U.S. constellation is not the only one in space. The Russian GLONASS constellation contains 18 satellites with a goal of 30 satellites by 2011. Adding these extra satellites to the U.S. GPS can make a significant improvement.
As well, the Chinese aerospace industry and the GPS company Trimble are developing a GPS constellation called Compass. The European Union is developing the Galileo constellation and Japan the QZSS constellation.
Trimble predicts an eventual shift from solely U.S. GPS to the Global Navigation Satellite System, an international constellation that would combine all worldwide satellite constellations into a single system.
Trimble antenna-receivers are already available that use signals from both GPS and GLONASS satellites.
Another backup option is to reactivate the ghost fleet of retired U.S. satellites that are still operational in normal GPS orbits. At least three could be re-commissioned.
As well, other satellites have been turned down or turned off to conserve power for use as backups. They can also be put back into full service.
Even before the GAO review was done, the Air Force Space Command knew of the risks and had a plan of action. From everything I’ve found, our GPS satellites are in good hands and we can look forward to an expansion of GPS services.
Pamela Haegeman grew up on a farm at Swan Lake, Man. She has an agriculture diploma from Olds College, a GIS diploma from Assiniboine College and a geomatics degree from Brandon University. She is the GPS/GIS specialist for Mazur Group in Brandon and the Manitoba Zero Till Research Farm. She can be reached at phaegeman@yahoo.com.
