How times change. In the 1990s, the Departments of State and Commerce, backed by the Department of Defense and the GPS industry, were busy persuading foreign nations that with GPS available to everyone worldwide, they shouldn’t waste their money launching their own satnav systems. But the genie got out of the bottle anyway.
Addressing the U.S. Institute of Navigation’s recent GNSS-2008 Conference in Savannah, Ga., the State Department’s Alice Wong stated that within the next decade five individual nations, plus the European Union (EU), will have among them 110 global satellites, 10 regional satellites and 13 WAAS-type augmentation satellites in orbit. The U.S. and Russia have GPS-like systems in place; the EU will launch its own by 2010, and China, India and Japan are planning their own.
Recognizing the political realities of the positioning, navigation and timing business, Washington has done a 180 since the early 1990s. The new U.S. position is to “encourage foreign development” of satnav services based on GPS.
There are currently 27 Block II version GPS satellites in operation, with periodic replacements launched as older satellites eventually fail. The DOD’s commitment is to have a minimum of 21 satellites operating at “98-percent probability averaged over one year.” More powerful, and more capable, Block III units will start entering the constellation in 2014, and will have replaced all the Block IIs by 2021. Two FAA-funded WAAS satellites are currently in orbit, with a third to be added in 2015.
Russia’s Glonass has 15 Type M satellites in orbit and will have 18 by year-end. Three were launched simultaneously on a Proton rocket on September 25, and another three are planned for December 25 launch. Prime Minister Putin earlier allocated $2.6 billion to upgrading the system, which is planned to have 30 satellites in orbit by 2011. All Glonass-M satellites will be progressively replaced by advanced technology -K versions after 2011, in a move said to keep up with the DOD’s GPS III and the EU’s Galileo. Currently, Russia has no plans for a WAAS equivalent.
Galileo has two test satellites now in orbit, with reportedly highly successful results. The first four operational satellites of the constellation are forecast to be in orbit by 2010, with 30 (27 active plus three spares) in place by 2013. Unlike GPS and Glonass, Galileo will charge fees for the use of special services, although its basic navigation signals will be free. Europe also has a three-satellite WAAS-like European GNSS Navigation Overlay System (Egnos) now completing operational testing for aviation certification by late next year.
China’s Compass system is planned to have 35 satellites, although details are sketchy. China has had four navigation satellites in high-altitude equatorial orbit for some years, but these have been used for military purposes, unlike the WAAS-type satellites elsewhere. They may become part of Compass, for which the first mid-altitude satellite has recently been launched. The full Compass constellation is expected to be operational in the 2015 to 2018 time frame.
India’s regional navigation satellite system (IRNSS) will have seven satellites, providing satnav services over the nation and to 200 or 300 miles beyond. The IRNSS operational timetable is reported to be similar to that of Compass, between 2015 and 2018. But well before those dates, India will have its three satellite WAAS-like Gagan (Hindi for sky) operational, possibly supplied by Raytheon, which built the FAA’s system.
Japan’s QZSS–for Quasi-Zenith Satellite System–will have three satellites orbiting in a figure-eight-shaped constellation by around 2012, where the satellites will pass high in the skies over Japan, to allow uninterrupted positioning deep into the urban canyons of the country’s major cities, where the lower-elevation GPS signals cannot reach. The QZSS satellites will be supported by two equatorial satellites, one of which is already in position, which will provide WAAS-type augmentation. The U.S. will monitor QZSS signals for Japan in Hawaii and Guam. A once proposed QZSS expansion, covering a much larger area and called the Japan Regional Air Navigation System, may have been shelved.
Current GPS Satellites Reach End of Lifespan
While some GPS satellites have lasted more than 15 years in space–twice their planned endurance–they don’t live forever, and their components slowly deteriorate, requiring routine replacements.
At the Institute of Navigation’s recent GNSS-2008 Conference in Savannah, Ga., USAF Lt. Joe Riedesel noted that of the 27 operational satellites plus five spares now in orbit:
• 19 are past their design life;
• 18 are one component away from navigation payload failure;
• and eight are one component away from bus failure.
The DOD’s minimum annual average configuration is 21 operational satellites, and loss of several satellites over a short period of time is considered extremely improbable. Yet there is a longer-term concern that the collision risk with “dead” navigation satellites will eventually become a serious problem.