A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and set "due west". This occurs twice each year, around 20 March and 23 September.
A satellite or artificial satellite is an object intentionally placed into orbit around a celestial body. Satellites have a variety of uses, including communication relay, weather forecasting, navigation (GPS), broadcasting, scientific research, and Earth observation. Additional military uses are reconnaissance, early warning, signals intelligence and, potentially, weapon delivery. Other satellites include the final rocket stages that place satellites in orbit and formerly useful satellites that later become defunct.
A solstice is an event that occurs when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countries, the seasons of the year are determined by the solstices and the equinoxes.
A geostationary orbit, also referred to as a geosynchronous equatorial orbit (GEO), is a circular geosynchronous orbit 35,786 km (22,236 mi) in altitude above Earth's equator, 42,164 km (26,199 mi) in radius from Earth's center, and following the direction of Earth's rotation.
A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit 22,300 miles (35,900 km) above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently.
A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite. The term most commonly means a dish which receives direct-broadcast satellite television from a direct broadcast satellite in geostationary orbit.
A very-small-aperture terminal (VSAT) is a two-way satellite ground station with a dish antenna that is smaller than 3.8 meters. The majority of VSAT antennas range from 75 cm to 1.2 m. Bit rates, in most cases, range from 4 kbit/s up to 16 Mbit/s. VSATs access satellites in geosynchronous orbit or geostationary orbit to relay data from small remote Earth stations (terminals) to other terminals or master Earth station "hubs".
A satellite telephone, satellite phone or satphone is a type of mobile phone that connects to other phones or the telephone network by radio link through satellites orbiting the Earth instead of terrestrial cell sites, as cellphones do. Therefore, they can work in most geographic locations on the Earth's surface, as long as open sky and the line-of-sight between the phone and the satellite are provided. Depending on the architecture of a particular system, coverage may include the entire Earth or only specific regions. Satellite phones provide similar functionality to terrestrial mobile telephones; voice calling, text messaging, and low-bandwidth Internet access are supported through most systems. The advantage of a satphone is that it can be used in such regions where local terrestrial communication infrastructures, such as landline and cellular networks, are not available.
Satellite Internet access or Satellite Broadband is Internet access provided through communication satellites. This technology enables users to access the Internet regardless of their geographical location. Modern consumer grade satellite Internet service is typically provided to individual users through geostationary satellites that can offer relatively high data speeds, with newer satellites using Ku band to achieve downstream data speeds up to 506 Mbit/s. In addition, new satellite internet constellations are being developed in low-earth orbit to enable low-latency internet access from space.
Inmarsat is a British satellite telecommunications company, offering global mobile services. It provides telephone and data services to users worldwide, via portable or mobile terminals which communicate with ground stations through fourteen geostationary telecommunications satellites. Inmarsat's network provides communications services to a range of governments, aid agencies, media outlets and businesses with a need to communicate in remote regions or where there is no reliable terrestrial network. The company was listed on the London Stock Exchange until it was acquired by Connect Bidco, a consortium consisting of Apax Partners, Warburg Pincus, the CPP Investment Board and the Ontario Teachers' Pension Plan, in December 2019.
In astronomy, a solar transit is a movement of any object passing between the Sun and the Earth. This mainly includes the planets Mercury and Venus. A solar eclipse is also a solar transit of the Moon, but technically only if it does not cover the entire disc of the Sun, as "transit" counts only objects that are smaller than what they are passing in front of. Solar transit is only one of several types of astronomical transit
Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna commonly referred to as a satellite dish and a low-noise block downconverter.
The Lincoln Experimental Satellite series was designed and built by Lincoln Laboratory at Massachusetts Institute of Technology between 1965 and 1976, under USAF sponsorship, for testing devices and techniques for satellite communication.
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 3,000 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications.
This is an index to articles about terms used in discussion of radio propagation.
Galaxy 15 is an American telecommunications satellite which is owned by Intelsat. It was launched for and originally operated by PanAmSat, and was subsequently transferred to Intelsat when the two companies merged in 2006. It was originally positioned in geostationary orbit at a longitude of 133° West, from where it was used to provide communication services to North America.
Elektro–L is a series of meteorological satellites developed for the Russian Federal Space Agency by NPO Lavochkin. The first satellite, Elektro-L No.1, was launched on 2 January 2011. It is the first Russian weather satellite that successfully operates in geostationary orbit, and is currently the second operational Russian weather satellite. The satellites have a mass of about 1620 kg and are designed to operate for 10 years each. They are capable of producing images of the Earth's whole hemisphere in both visible and infrared frequencies, providing data for climate change and ocean monitoring in addition to their primary weather forecasting role.
Maritime VSAT is the use of satellite communication through a Very-small-aperture terminal (VSAT) on a moving ship at sea. Since a ship at sea moves with the water, the antenna needs to be stabilized with reference to the horizon and True north, so that the antenna is constantly pointing at the satellite it uses to transmit and receive signals.
GOES-17 is an environmental satellite operated by the National Oceanic and Atmospheric Administration (NOAA). The satellite is second in the four-satellite GOES-R series. GOES-17 supports the Geostationary Operational Environmental Satellite (GOES) system, providing multi-spectral imaging for weather forecasts and meteorological and environmental research. The satellite was built by Lockheed Martin, based on the A2100A platform, and expected to have a useful life of 15 years. GOES-17 is intended to deliver high-resolution visible and infrared imagery and lightning observations of more than half the globe.
