Gulyás Katalin et al. (szerk.): Tisicum. A Jász-Nagykun-Szolnok megyei Múzeumok évkönyve 28. (Szolnok, 2020)
Történettudomány - Csaba Kasza: Evolution and human benefits of the GPS
Csaba Kasza Evolution and human benefits of the GPS The Global Positioning System (GPS) is the principal component and the only fully operational element of the Global Navigation Satellite System (GNSS). The history of the GPS program pre-dates the space age. In 1951, Dr. Ivan Getting1 designed a three-dimensional, position-finding system based on time difference of arrival of radio signals. Shortly after the launch of Sputnik scientists confirmed that Doppler distortion could be used to calculate ephemerides, and, conversely, if a satellite's position was known, the position of a receiver on earth could be determined. Within two years of the launch of Sputnik the first of five lowaltitude “Transit” satellites for global navigation were launched. In 1967, the first of three “Timation” satellites demonstrated that highly accurate clocks could be carried in space. In parallel with these efforts, the 621B2 program was developing many of the characteristics of today’s GPS system. In 1973 these parallel efforts were brought together into the NAVSTARGlobal Positioning System, managed by a joint program office headed by then-colonel Dr. Brad Parkinson3 at the United States Air Force, Space and Missile Systems Organization. This office developed the GPS architecture and initiated the development of the first satellites, the worldwide control segment and ten types of user equipment. Today, it continues to sustain the system as the Global Positioning System Directorate of the Space and Missile Systems Center. All performance parameters for the system were verified during ground testing by 1978. Ten development satellites were launched successfully between 1978 and 1985 and the initial ground segment that would provide the critical uploads to the satellites was also developed. The initial constellation of 24 operational satellites were deployed between 1989 and 1994 and the system was declared “fully operational” in 1995. It has been sustained at that level or higher ever since. The initial operational satellites transmitted authorized signals on two frequencies, designated L1 and L2, and a signal intended for open (civilian) use on the L1 frequency. GPS is currently engaged in a modernization program that will bring new and improved services to the global user community through new generations of satellites, referred to as Blocks. With the first Block IIR-M satellite (in 2005), a second civil signal was added (to L2) improving the quality of the system for civil users. Seven of these satellites are on orbit. With the first Block IIF satellite (in 2010), a third signal (L5) was added to help ensure the availability of GPS to civil aeronautical and search-and-rescue users (called the safety of life signal). The next generation of GPS satellites, GPS Block III, is in production. They will transmit another new civil signal on L1 that will provide 1 Dr Ivan Getting (1912-2003) American physicist and electrical engineer. 2 621 B program new satellite based navigational system. 3 Dr Brad Parkinson (1935) US Air Force colonel, inventor, engineer - he is the leader of the first GPS satellite launching in 1978. more power and enable greater civil interoperability with other global and regional elements of the GNSS, such as Europe’s Galileo system, Japan’s Quazi-Zenith Satellite System and others. In 1983, following the shoot-down of KAL-0074 after straying off-course into prohibited airspace, the President of the United States directed that GPS would be made available for civilian use as a common good. The GPS civil signal was initially slightly degraded due to its potential military implications. However, in 2000, the President directed that the quality of the signal available to civilian users would no longer be degraded. In 2004, the President released a new U.S. National Space-based Positioning, Navigation, and Timing Policy. The 2004 policy placed the GPS system under the oversight of a National Space-based Positioning, Navigation and Timing Executive Committee that is co-chaired by the US Deputy Secretaries of Transportation and Defense, and made up of nine Departments and Agencies across the U.S. Government. Although GPS was originally viewed as a unique capability, other nations have recognized the importance of this technology to their critical infrastructures and economies and are now in various stages of implementing GPS-like systems of their own. The GPS program has worked hard to ensure these multiple satellite-based navigation and timing systems can operate with compatibility, interoperability and transparency for all open signals. GPS made major technical contributions to analysis techniques that predict compatibility, so systems can share spectrum for interoperability while ensuring radio frequency compatibility is attained. In bilateral working groups and multinational fora, the U.S. Government and representatives from Japan, Europe, India, Russia, and China and other nations have moved toward common signal designs on L1 and L5 frequencies that will be used by civil signals in almost every system of the GNSS. GPS has become a ubiquitous utility, required to be available to civil users around the world, at no cost, providing unprecedented timing, position and navigation accuracies with almost incalculable human benefits, it was developed initially as a military system. It is now the underpinning of incredibly broad civil applications and also, in keeping with its origins, amazingly accurate precision strike systems. This also has significant human benefit, since when conflict cannot be avoided, the history of the last two decades has shown that collateral damage and civilian casualties resulting from military actions are significantly less than was seen in pre-GPS conflicts. 4 South Korean Airlines Flight 007. 233
