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Commercial Crew Program
The Commercial Crew Program is a NASA program, established in 2010, that buys astronaut transportation to the International Space Station from private companies Boeing and SpaceX.
Commercial Lunar Payload Services
Commercial Lunar Payload Services, or CLPS, is a NASA initiative, established in 2018, that contracts American companies to deliver science and technology payloads to the Moon's surface and orbit.
Commercial Resupply Services
Commercial Resupply Services (CRS) is a NASA program under which private American companies deliver cargo, experiments, and supplies to the International Space Station under fixed-price contracts.
Common Interface
The Common Interface, or DVB-CI, is a DVB-standard slot that connects a removable conditional access module to a TV or set-top box to descramble pay-TV channels, published in 1997.
Communications satellite
A communications satellite is a spacecraft that relays radio signals between ground stations or other spacecraft using transponders, enabling telephone, television, data, and broadband services without terrestrial cables.
Communications Satellite Act of 1962
The Communications Satellite Act of 1962, the Comsat Bill, is a US federal law signed by President Kennedy on August 31, 1962, establishing a commercial global satellite system.
Comparison of orbital launch systems
A comparison of orbital launch systems, the rockets and infrastructure that place payloads into Earth orbit, ranked by payload mass to a stated orbit, reusability, launch cadence, reliability, and cost per kilogram.
Comparison of orbital launch vehicle families
A comparison of orbital launch vehicle families, rockets sharing common engines or development lineage, covering payload capacity, cost per kilogram, reliability records, reusability, and country of origin.
Compton Gamma Ray Observatory
The Compton Gamma Ray Observatory (CGRO), also called Compton, was a NASA space observatory that studied the gamma-ray sky from 1991 to 2000 as the second of NASA's Great Observatories.
Comstar (satellite)
Comstar was a series of four American geostationary domestic communications satellites built by Hughes Aircraft for Comsat General, launched from Cape Canaveral between 1976 and 1981.
Conestoga (rocket)
Conestoga was a family of American solid-propellant rockets by Space Services Inc. and EER Systems; its Conestoga I of 1982 was the first privately funded rocket to reach space.
Congressional Space Medal of Honor
The Congressional Space Medal of Honor, also known as the Space Medal of Honor, is the highest award the United States gives to astronauts, first presented in 1978.
Conjunction assessment
Conjunction assessment is the process of predicting close approaches between orbiting space objects, computing the risk of collision, and deciding whether an avoidance maneuver is needed. It is the operational core of satellite collision avoidance.
Conroy Virtus
The Conroy Virtus was a proposed twin-fuselage American aircraft, designed in 1974 by John M. Conroy to carry the Space Shuttle Orbiter, using B-52 fuselage sections; NASA chose a 747 instead.
Constellation program
The Constellation program was a NASA program announced in 2004 to return astronauts to the Moon by 2020, canceled before any of its vehicles flew operationally.
Continuously Operating Reference Station
A Continuously Operating Reference Station (CORS) is an automated GNSS receiver at a precisely surveyed location that records satellite data around the clock for high-accuracy positioning.
CONTOUR
CONTOUR (Comet Nucleus TOUR) was a NASA Discovery Program spacecraft launched in 2002 to fly by comet nuclei including 2P/Encke, lost six weeks after launch.
Control moment gyroscope
A control moment gyroscope (CMG) is a spacecraft attitude-control actuator that steers a constant-speed rotor's momentum with gimbals, giving large torque without propellant, flown on Skylab and the ISS.
Controlled ecological life-support system
A controlled ecological life-support system, or CELSS, is a closed engineered ecosystem that recycles food, oxygen, and water for space crews, studied by NASA from 1978.
Controlled reentry and deorbit
Controlled reentry and deorbit is the deliberate disposal of a spacecraft or rocket stage by firing its propulsion to steer surviving debris into a predetermined, unpopulated ocean zone.
Copernicus Land Monitoring Service
The Copernicus Land Monitoring Service, run by the European Environment Agency and Joint Research Centre, provides land cover data for Europe and worldwide since 2012.
Copernicus Programme
Copernicus is the European Union's Earth observation program, run by the European Commission with ESA, whose Sentinel satellites monitor land, oceans, atmosphere, and climate with free open data.
Copernicus satellite
Copernicus, also called Orbiting Astronomical Observatory 3 (OAO-3), was a NASA ultraviolet and X-ray astronomy satellite launched in 1972 and operated until 1981, carrying the largest ultraviolet telescope orbited to that date.
COROT
COROT (Convection, Rotation and planetary Transits) was a French-led space telescope for stellar seismology and finding transiting exoplanets, launched in 2006 and operated until 2013.
COSMIC (satellite constellation)
COSMIC, also known in Taiwan as FORMOSAT-3, is a six-satellite US–Taiwan constellation launched in 2006 that pioneered GPS radio occultation, profiling the atmosphere and ionosphere.
Cosmic Origins Spectrograph
The Cosmic Origins Spectrograph (COS) is an ultraviolet spectrograph installed on the Hubble Space Telescope in May 2009 to study how galaxies, stars, and planets formed.
COSMO-SkyMed
COSMO-SkyMed (COnstellation of small Satellites for Mediterranean basin Observation) is an Italian Earth observation program of X-band synthetic aperture radar satellites for dual civilian and military use, first launched in 2007.
Crawler-transporter
The crawler-transporter is a pair of giant tracked NASA vehicles, formally the Missile Crawler Transporter Facilities, that carry rockets from the Vehicle Assembly Building to the launch pads.
Crew Dragon Demo-2
Crew Dragon Demo-2, also known as SpaceX DM-2, was SpaceX's first crewed test flight, carrying NASA astronauts Robert Behnken and Douglas Hurley to the International Space Station in 2020.
Crew Dragon Grace
Crew Dragon Grace is the fifth and final Crew Dragon spacecraft built by SpaceX, flying Axiom Mission 4 in June 2025 and NASA's Crew-13 in October 2026.