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Indian Regional Navigation Satellite System
The Indian Regional Navigation Satellite System (IRNSS), officially Navigation with Indian Constellation (NavIC), is India's independent regional satellite navigation system operated by ISRO over India and surrounding areas.
Inertial Upper Stage
The Inertial Upper Stage (IUS) is a two-stage, solid-fuel booster developed by the US Air Force and NASA, flown with the Space Shuttle and Titan rockets from 1982 to 2004.
Ingenuity (helicopter)
Ingenuity, also known as the Mars Helicopter, was a small NASA rotorcraft that achieved the first powered, controlled flight on another planet in April 2021.
Inmarsat
Inmarsat is a British satellite telecommunications company providing mobile communications to ships, aircraft, and land users; established in 1979 and privatized in 1999, it operates as part of Viasat.
InSight
InSight was a NASA Discovery-program Mars lander that operated on Mars from November 2018 to December 2022, placing the first seismometer on the Martian surface and recording 1,319 marsquakes.
Inspiration4
Inspiration4 was a privately chartered SpaceX flight that launched four civilian astronauts into orbit on September 15, 2021, the first orbital human spaceflight with no professional government astronauts aboard.
Integrated Truss Structure
The Integrated Truss Structure, or ISS Truss, is the backbone of the International Space Station: 11 segments carrying its solar arrays, thermal radiators, and external payloads, assembled by shuttle from 2002.
Intelsat 708
Intelsat 708 was a commercial communications satellite built by Space Systems/Loral, destroyed in February 1996 when its Long March 3B rocket crashed after liftoff in China.
Intelsat I
Intelsat I, originally named Early Bird, was the world's first commercial communications satellite, launched from Cape Kennedy in 1965 to link North America and Western Europe.
Intelsat IV
Intelsat IV was a series of seven geostationary communications satellites built by Hughes Aircraft for INTELSAT, launched between 1971 and 1975 to carry global telephone and television traffic.
Intelsat V
Intelsat V was a series of nine commercial communications satellites built by Ford Aerospace for INTELSAT, launched between 1980 and 1984 to carry telephone, television, and data traffic.
Intelsat VI
Intelsat VI was a series of five Hughes geostationary communications satellites launched between 1989 and 1991, at the time the largest commercial satellites ever built.
Interball
Interball (ИНТЕРБОЛ) was a Russian-led program of four spacecraft in two pairs, launched in 1995 and 1996, that studied plasma processes in Earth's magnetosphere and solar wind.
Interface Region Imaging Spectrograph
The Interface Region Imaging Spectrograph (IRIS) is a NASA Small Explorer satellite launched in 2013 to study the Sun's chromosphere and transition region and how the corona heats up.
Interkosmos (satellite series)
Interkosmos (Интеркосмос) was a series of scientific Earth satellites launched by the Soviet Union from 1969 to 1991, carrying instruments from socialist partner countries to study the Sun, ionosphere, and magnetosphere.
International Cometary Explorer
The International Cometary Explorer (ISEE-3) was a NASA spacecraft, launched in 1978 as the first to orbit the Sun-Earth L1 point, that flew through Comet Giacobini-Zinner's tail in 1985.
International Lunar Research Station
The International Lunar Research Station (ILRS) is a planned lunar base proposed by China and Russia in 2021, targeting a basic station at the lunar south pole by 2035.
International satellite registration
International satellite registration is the dual system by which States record satellites through ITU spectrum filings and UN registration under the Outer Space Treaty and the 1975 Registration Convention.
International Space Station
The International Space Station (ISS, МКС) is a permanently crewed research laboratory in low Earth orbit, assembled by more than 40 flights and continuously occupied since November 2000.
Interplanetary Internet
The Interplanetary Internet, also known as space internet, is a proposed communication architecture using delay-tolerant networking, begun at NASA's Jet Propulsion Laboratory in 1998 by Vint Cerf and Adrian Hooke.
Interplanetary spaceflight
Interplanetary spaceflight, also called interplanetary travel, is the flight of spacecraft between planets of the Solar System, from launch through cruise to arrival, using trajectories shaped by orbital mechanics and gravity assists.
Interplanetary Transport Network
The Interplanetary Transport Network, or Interplanetary Superhighway, is a network of gravitationally determined pathways letting spacecraft travel between planets with little propellant at the cost of longer flight times.
Interpretations of 2001: A Space Odyssey
Interpretations of 2001: A Space Odyssey concern the meanings assigned to Stanley Kubrick and Arthur C. Clarke's 1968 film, whose monolith, HAL 9000, and Star Child are never explained.
Interstellar Boundary Explorer
The Interstellar Boundary Explorer (IBEX) is a NASA Small Explorer satellite launched in 2008 that maps the outer edge of the heliosphere and discovered the unexpected IBEX ribbon.
Interstellar travel
Interstellar travel is the movement of spacecraft between stars. Only Voyager 1 and Voyager 2 have reached interstellar space; travel to other stars remains beyond current technology.
Intuitive Machines
Intuitive Machines is an American space exploration company founded in Houston, Texas in 2013, best known for landing Odysseus on the Moon in 2024, the first commercial lunar landing.
Ion thruster
An ion thruster is a spacecraft engine that ionizes propellant, typically xenon, and accelerates the ions to produce gentle, efficient thrust. First flown in 1964, it now propels deep-space missions and satellites.
Ionospheric Connection Explorer
Ionospheric Connection Explorer, known as ICON, was a NASA satellite launched in 2019 to study how terrestrial weather and space weather combine to drive Earth's ionosphere.
Iridium Communications
Iridium Communications Inc. is an American satellite communications company in McLean, Virginia, operating 66 cross-linked low Earth orbit satellites with global voice and data coverage, launched in 1998 after originating as a Motorola concept in 1987.
Iridium NEXT
Iridium NEXT is the second-generation constellation of Iridium Communications, a network of 66 low Earth orbit satellites that replaced the original 1990s-era fleet between 2017 and 2019 without interrupting service.