Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high-definition television (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio in contrast to the narrower format (4:3) of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in the same bandwidth as a single analog channel, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:
Slow-scan television (SSTV) is a picture transmission method, used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or color.
Radiofacsimile, radiofax or HF fax is an analogue mode for transmitting monochrome images via high frequency (HF) radio waves. It was the predecessor to slow-scan television (SSTV). It was the primary method of sending photographs from remote sites from the 1930s to the early 1970s. It is still in limited use for transmitting weather charts and information to ships at sea.
The low-rate picture transmission (LRPT) is a digital transmission system, intended to deliver images and data from an orbital weather satellite directly to end users via a VHF radio signal. It is used aboard polar-orbiting, near-Earth weather satellite programs such as MetOp and NPOESS.
WSJT-X is a computer program used for weak-signal radio communication between amateur radio operators. The program was initially written by Joe Taylor, K1JT, but is now open source and is developed by a small team. The digital signal processing techniques in WSJT-X make it substantially easier for amateur radio operators to employ esoteric propagation modes, such as high-speed meteor scatter and moonbounce. Additionally WSJT is able to send signal reports to spotting networks such as PSK Reporter.
NOAA-17, also known as NOAA-M before launch, was an operational, polar orbiting, weather satellite series operated by the National Environmental Satellite Service (NESS) of the National Oceanic and Atmospheric Administration (NOAA). NOAA-17 also continued the series of Advanced TIROS-N (ATN) spacecraft begun with the launch of NOAA-8 (NOAA-E) in 1983 but with additional new and improved instrumentation over the NOAA A-L series and a new launch vehicle.
NOAA-16, also known as NOAA-L before launch, was an operational, polar orbiting, weather satellite series operated by the National Environmental Satellite Service (NESS) of the National Oceanic and Atmospheric Administration (NOAA). NOAA-16 continued the series of Advanced TIROS-N (ATN) spacecraft that began with the launch of NOAA-8 (NOAA-E) in 1983; but it had additional new and improved instrumentation over the NOAA A-K series and a new launch vehicle. It was launched on 21 September 2000 and, following an unknown anomaly, it was decommissioned on 9 June 2014. In November of 2015 it broke up in orbit, creating more than 200 pieces of debris.
NOAA-18, also known as NOAA-N before launch, is an operational, polar orbiting, weather satellite series operated by the National Environmental Satellite Service (NESS) of the National Oceanic and Atmospheric Administration (NOAA). NOAA-18 also continued the series of Advanced TIROS-N (ATN) spacecraft begun with the launch of NOAA-8 (NOAA-E) in 1983 but with additional new and improved instrumentation over the NOAA A-M series and a new launch vehicle. NOAA-18 is in an afternoon equator-crossing orbit and replaced NOAA-17 as the prime afternoon spacecraft.
NOAA-15, also known as NOAA-K before launch, is an operational, polar-orbiting of the NASA-provided Television Infrared Observation Satellite (TIROS) series of weather forecasting satellite operated by National Oceanic and Atmospheric Administration (NOAA). NOAA-15 was the latest in the Advanced TIROS-N (ATN) series. It provided support to environmental monitoring by complementing the NOAA/NESS Geostationary Operational Environmental Satellite program (GOES).
In radio, cooperative multiple-input multiple-output is a technology that can effectively exploit the spatial domain of mobile fading channels to bring significant performance improvements to wireless communication systems. It is also called network MIMO, distributed MIMO, virtual MIMO, and virtual antenna arrays.
The technology of television has evolved since its early days using a mechanical system invented by Paul Gottlieb Nipkow in 1884. Every television system works on the scanning principle first implemented in the rotating disk scanner of Nipkow. This turns a two-dimensional image into a time series of signals that represent the brightness and color of each resolvable element of the picture. By repeating a two-dimensional image quickly enough, the impression of motion can be transmitted as well. For the receiving apparatus to reconstruct the image, synchronization information is included in the signal to allow proper placement of each line within the image and to identify when a complete image has been transmitted and a new image is to follow.
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.
NOAA-13, also known as NOAA-I before launch, was an American weather satellite operated by the National Oceanic and Atmospheric Administration (NOAA). NOAA-I continued the operational, polar orbiting, meteorological satellite series operated by the National Environmental Satellite System (NESS) of the National Oceanic and Atmospheric Administration (NOAA). NOAA-I continued the series (fifth) of Advanced TIROS-N (ATN) spacecraft begun with the launch of NOAA-8 (NOAA-E) in 1983. NOAA-I was in an afternoon equator-crossing orbit and was intended to replace the NOAA-11 (NOAA-H) as the prime afternoon (14:00) spacecraft.
Weather satellite pictures are often broadcast as high-resolution picture transmissions (HRPTs), color high-resolution picture transmissions (CHRPTs) for Chinese weather satellite transmissions, or advanced high-resolution picture transmissions (AHRPTs) for EUMETSAT weather satellite transmissions. HRPT transmissions are available around the world and are available from both polar and geostationary weather satellites. The polar satellites rotate in orbits that allow each location on Earth to be covered by the weather satellite twice per day while the geostationary satellites remain in one location at the equator taking weather images of the Earth from that location over the equator. The sensor on weather satellites that picks up the data transmitted in HRPT is referred to as an Advanced Very High Resolution Radiometer (AVHRR).
A ground segment consists of all the ground-based elements of a space system used by operators and support personnel, as opposed to the space segment and user segment. The ground segment enables management of a spacecraft, and distribution of payload data and telemetry among interested parties on the ground. The primary elements of a ground segment are:
Kosmos 144, was launched on 28 February 1967, Meteor No.6L, and was one of eleven weather satellites launched by the Soviet Union between 1964 and 1969. Kosmos 144 was the second announced Russian meteorological satellite and the first interim operational weather satellite in the experimental Kosmos satellite 'Meteor' system. It was also the first launch of the semi-operational weather satellite from the Plesetsk site into a near-polar, near-circular orbit. Unlike U.S. weather satellites, however, the orbit was prograde because, as a result of geographic limitations, a retrograde orbit was not possible. Kosmos 144 was orbited to test, in a semi-operational mode, meteorological instruments designed for obtaining images of cloud cover, snow cover, and ice fields on the day and night sides of the Earth and for measuring fluxes of outgoing radiation reflected and radiated by the Earth-atmosphere system.
NOAA-9, known as NOAA-F before launch, was an American weather satellite operated by the National Oceanic and Atmospheric Administration (NOAA) for use in the National Environmental Satellite Data and Information Service (NESDIS). It was the second of the Advanced TIROS-N series of satellites. The satellite design provided an economical and stable Sun-synchronous platform for advanced operational instruments to measure the atmosphere of Earth, its surface and cloud cover, and the near-space environment.
NOAA-10, known as NOAA-G before launch, was an American weather satellite operated by the National Oceanic and Atmospheric Administration (NOAA) for use in the National Environmental Satellite Data and Information Service (NESDIS). It was the third of the Advanced TIROS-N series of satellites. The satellite design provided an economical and stable Sun-synchronous platform for advanced operational instruments to measure the atmosphere of Earth, its surface and cloud cover, and the near-space environment.
NOAA-12, also known as NOAA-D before launch, was an American weather satellite operated by National Oceanic and Atmospheric Administration (NOAA), an operational meteorological satellite for use in the National Environmental Satellite, Data, and Information Service (NESDIS). The satellite design provided an economical and stable Sun-synchronous platform for advanced operational instruments to measure the atmosphere of Earth, its surface and cloud cover, and the near-space environment.
NOAA-14, also known as NOAA-J before launch, was an American weather satellite operated by the National Oceanic and Atmospheric Administration (NOAA). NOAA-14 continued the third-generation operational, Polar Orbiting Environmental Satellite (POES) series operated by the National Environmental Satellite Service (NESS) of the National Oceanic and Atmospheric Administration (NOAA). NOAA-14 continued the series of Advanced TIROS-N (ATN) spacecraft begun with the launch of NOAA-8 (NOAA-E) in 1983.
