The K_a band (pronounced as either "kay-ay band" or "ka band") is a portion of the

microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...

part of the

electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging fro ...

defined as

frequencies Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is e ...

in the range 26.5–40

gigahertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

(GHz), i.e. wavelengths from slightly over one centimeter down to 7.5 millimeters. The band is called K_a, short for "K-above" because it is the upper part of the original NATO K band, which was split into three bands because of the presence of the atmospheric

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous p ...

resonance peak at 22.24 GHz (1.35 cm), which made the center unusable for long range transmission. The 30/20 GHz band is used in

communications satellite 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 ...

uplink In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or sha ...

s in either the 27.5 GHz and 31 GHz bands, and high-resolution, close-range targeting

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

s aboard military airplanes. Some frequencies in this radio band are used for vehicle speed detection by law enforcement. The

Kepler Mission The Kepler space telescope is a disused space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orbi ...

used this frequency range to downlink the scientific data collected by the space telescope. The designation "K_a-band" is from Kurz-above, which stems from the German word ''kurz'' meaning "short". In satellite communications, the K_a band allows higher bandwidth communication. It was first used in the experimental ACTS Gigabit Satellite Network, and is currently used for high-throughput

satellite Internet access Satellite Internet access is Internet access provided through communication satellites. Modern consumer grade satellite Internet service is typically provided to individual users through geostationary satellites that can offer relatively high d ...

in geostationary orbit (GEO) by the Inmarsat I-5 system and Kacific K-1 satellite; in low Earth orbit (LEO) by the

SpaceX Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal o ...

Starlink Starlink is a satellite internet constellation operated by SpaceX, providing satellite Internet access coverage to 45 countries. It also aims for global mobile phone service after 2023. SpaceX started launching Starlink satellites in 2019. As ...

system and the

Iridium Next The Iridium satellite constellation provides L band voice and data information coverage to satellite phones, pagers and integrated transceivers over the entire surface of Earth. Iridium Communications owns and operates the constellation, addi ...

satellite series; it is also use in medium Earth orbit (MEO) by the SES

O3b O3b is a satellite constellation in Medium Earth orbit (MEO) owned and operated by SES, and designed to provide low-latency broadband connectivity to remote locations for mobile network operators and internet service providers, maritime, aviat ...

system; and the

James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope which conducts infrared astronomy. As the largest optical telescope in space, its high resolution and sensitivity allow it to view objects too old, distant, or faint for the Hubble Sp ...

. Planned future satellite projects using K_a-band include

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satellite internet constellation A satellite internet constellation is a constellation of artificial satellites providing satellite internet service. In particular, the term has come to refer to a new generation of very large constellations (sometimes referred to as a megaco ...

in LEO, SES's multi-orbit satellite internet system of the

SES-17 SES-17, is a high throughput all electric geostationary communications satellite owned and operated by SES S.A., and designed and manufactured by Thales Alenia Space. Launched on 24 October 2021 from Centre Spatial Guyanais (CSG), in Kourou, ...

satellite in GEO (launched in October 2021; in position and fully operational in June 2022) and O3b mPOWER constellation in MEO (to be launched 2022–2024, and starting service in Q3 2023). The K_a band is more susceptible to rain attenuation than is the , which in turn is more susceptible than the C band. The frequency is commonly used by

cosmic microwave background experiments This list is a compilation of experiments measuring the cosmic microwave background (CMB) radiation anisotropies and polarization since the first detection of the CMB by Penzias and Wilson in 1964. There have been a variety of experiments to ...

. The 5th generation mobile networks will also partially overlap with K_a band (28, 38, and 60 GHz).

References

Microwave bands Satellite broadcasting {{electromagnetism-stub