Navigation
Global navigation satellite systems (GNSS) provide highly accurate information for timing, position determination and navigation, globally and in all weather conditions. Satellite-based navigation has become a global utility with enormous daily benefits to people on the ground in a wide variety of areas such as aviation, maritime and land transportation, mapping and surveying, precision agriculture, power distribution and communications networks, as well as disaster warning and emergency response.
Navigation satellite systems comprise a constellation of satellites in orbit, where several satellites are simultaneously visible from any given point on the Earth at any given time. Each satellite emits a signal which can be detected by a receiver on the ground, and the combination of these signals yields time and position information. The technique used to decipher the signals was originally developed by astronomers for radar studies of the Moon and nearby planets.
The major systems in operation at the moment include the U.S. Global Positioning System (GPS), with 21 operational satellites and a similar Russian Global Navigation Satellite System (GLONASS). These systems are soon to be joined by the European Galileo system, further extending the benefits of GNSS to people on the ground.
The atomic clocks in GPS satellites provide timing for the Internet, cellular phone networks, ATM networks and other networks where a reliable, precise time standard is necessary. By combining GNSS data with satellite images and computer mapping techniques, we are better able to identify and manage our natural resources. Navigation satellites are used to track fishing vessels and vehicles transporting hazardous materials. Businesses with large amounts of mobile assets can manage their resources more efficiently, reducing consumer costs. In future, intelligent vehicle location and navigation systems will allow us to avoid congested freeways and find more efficient routes to our destinations, saving fuel and reducing air pollution.
Navigation satellites can support environmental monitoring and protection by measuring atmospheric temperature and humidity, which is important for our understanding of global climate and weather. These systems also support nature conservation by allowing the tracking of wild animals over rough or inaccessible terrain. Scientists also use satellite positioning measurements in conjunction with other techniques to study the crustal dynamics of the Earth. Navigation satellites are even used to support navigation in space by other satellites.
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Hubble directly observes Planet Orbiting Fomalhaut.
