The Global Positioning System (GPS) is a constellation of at least 24 satellites transmitting radio signals to users in order to provide positioning, navigation, and timing. Global civil GPS service has been available worldwide since 1993, continuously and free of direct user fees. Both our generation and economy depend on technological infrastructure and GPS, yet GPS signals are vulnerable to intentional and unintentional disruption.
Communications, energy, emergency, transportation and space satellite deployment all depend on GPS, and the loss of GPS signals could have unimaginable impacts on our society. Over the past few years, the US government has started upgrading GPS space satellites with new features through a multi-billion dollar effort to improve the overall performance of GPS. Older GPS satellites that have been in orbit for the past 30 years are being replaced with GPS IIR(M), GPS IIF, and GPS III.
Generations of Operational GPS Satellites
• Block IIA – 0 Operational 5 Residual
– 7-year design life
– Launched from 1990 through 1997
• Block IIR - 12 Operational
– 7-year design life (oldest operational satellite is 19 years old)
– Launched from 1997 through 2004
• Block IIR-M - 7 Operational, 1 Residual
– 7-year design life
– Launched from 2005 through 2009
– 2nd civil navigation signal (L2C)
• Block IIF - 12 Operational
– 12-year design life
– Launched from 2010 through 2016
– 3rd civil navigation signal (L5)
• GPS III is the newest block of GPS satellites to be concluded in the late 2020s
– 4 civil signals: L1 C/A, L1C, L2C, L5
– First satellites to broadcast common L1C signal
– 4 military signals: L1/L2 P(Y), L1/L2M
– 3 improved Rubidium atomic clocks
Global satellite positioning and timing depends on atomic clocks, based on Einstein’s calculations and invented by Isidor Rabi. An atomic clock uses atomic beam magnetic resonance and calculates the vibrations of caesium molecules. Each GPS satellite has an atomic clock to be used for timing calculations. In 1967, atomic clocks were proved to be accurate to as much as 1 second in 100,000 years, and are currently used by many nations in order to determine the national time, as well as in satellites.
GPS enhances everyday civil life, for GPS receivers enable and improve aviation, search and rescue, surveying and mapping, trucking and shipping, fishing, tracking, space exploration, offshore drilling, and also have many scientific uses. GPS has been used in planes, cars, trains, boats, watches and cell phones, as well as for improving productivity and efficiency in many areas. GPS also furthers scientific aims, such as weather forecasting, earthquake prediction, and environmental protection. Furthermore, the precise GPS time signal, derived from atomic clocks, is embedded in critical economic activities such as synchronising communication networks, managing power grids, and authenticating electronic transactions.
The US encourages GPS compatibility with foreign GNSS services and promotes transparency in civil use. The new GPS signals are designed to enable interoperability between international satellite navigation systems such as Galileo and GLONASS. The main focus of the new GPS program is to add new signals to the satellite constellation. The United States and Europe originally developed L1C as a common civil signal for GPS and Galileo. Japan's Quasi-Zenith Satellite System (QZSS) and China's BeiDou system are also adopting L1C-like signals. A new generation of GPS satellites is currently in production, and GPS III will begin launching in 2017, to be available on 24 satellites in the late 2020s.
As of February 2017, there are 31 operational GPS satellites in the orbit. Nineteen of these satellites broadcast L2C and the other twelve broadcast L5 signals. All twelve of the GPS IIF satellites have been launched and placed in orbit. Currently, the US is working on the GPS III. The new constellation of satellites will enhance signal reliability and accuracy and have a 15-year design lifespan. The US Air Force has given the production contract of GPS III satellites to Boeing, Lockheed Martin and Northrop Grumman to produce high-quality hardware.
To enable worldwide usage of satellite positioning (GNSS / Global Navigation Satellite Systems), GPS receivers can receive signals from USA’s NAVSTAR Global Positioning System (GPS), Russia’s Global'naya Navigatsionnaya Sputnikovaya Sistema (GLONASS), India’s Regional Navigational Satellite System (IRNSS), Japan’s Quasi-Zenith Satellite System (QZSS), China’s BeiDou and Europe’s Galileo satellite systems. GNSS is the standard generic term for global satellite navigation systems that provide global GPS coverage. As of today, GNSS receivers have been used in drones, IOT products, sensors, intelligent transport systems and GPS tracking systems, and half of all current GPS receivers in use can receive signals from two or more GNSS systems. Seven billion GPS receivers are being used in all sorts of vehicles and devices in 2017, and it is supposed to reach ten billion by 2023.
After the deployment of new satellites, the accuracy, uptime and accessibility of GPS will improve all around the world. Technology has been moving at a rapid pace in the 21st century, and GPS is no exception. With the development of new software, the new generation of GPS vehicle trackers in the 2020s will have an increased accuracy, up to centimetres close to an asset. The future of GPS tracking is going to be more accurate and effective for personal tracking, as well as business use.
More information on new satellites and GPS modernization can be found on gps.gov..