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Criticism of the Space Shuttle program
Criticism of the Space Shuttle program is the technical, economic, and organizational critique of NASA's reusable launch system, which flew 135 missions from 1981 until retirement in 2011.
Crosslink
A crosslink is a direct communication link between two or more satellites that bypasses ground stations, first demonstrated by MIT Lincoln Laboratory's LES 8 and 9 in 1978.
Cryogenic propellant
A cryogenic propellant is a rocket fuel or oxidizer, such as liquid oxygen or liquid hydrogen, that stays liquid only at extremely low temperatures and gives the highest performance among liquid propellants.
Cryogenic rocket engine
A cryogenic rocket engine is a liquid-propellant rocket engine that burns propellants stored at extremely low temperatures, most commonly liquid oxygen with liquid hydrogen or liquid methane.
CryoSat-2
CryoSat-2 is a European Space Agency Earth Explorer satellite, launched in 2010 to measure polar sea-ice thickness and monitor changes in the ice sheets of Greenland and Antarctica.
CSO (satellite)
CSO (Composante Spatiale Optique) is a French military Earth-observation system of three identical satellites providing very-high-resolution visible and infrared imagery, launched between 2018 and 2025 as part of the MUSIS program.
CubeSat
A CubeSat, or U-class satellite, is a miniaturized research satellite built in multiples of a 10 cm cube, a standard created in 1999 to give students and small teams cheap access to space.
Cupola (ISS module)
The Cupola is an ESA-built observatory module on the International Space Station, a seven-window dome installed in 2010 that gives crews a view of Earth and spacecraft.
Curiosity (rover)
Curiosity is a car-sized robotic rover of NASA's Mars Science Laboratory mission, landed by sky crane in Gale crater on Mars in 2012, still exploring Mount Sharp.
CYGNSS
CYGNSS, the Cyclone Global Navigation Satellite System, is a NASA Earth Venture mission of eight microsatellites, launched in 2016, that measures near-surface ocean winds to improve hurricane forecasting.
Cygnus (spacecraft)
Cygnus is an uncrewed cargo spacecraft, originally built by Orbital Sciences and now made by Northrop Grumman, that delivers supplies to the International Space Station since 2013.
Dan M. Goebel
Dan M. Goebel is a JPL Fellow and electric propulsion scientist at NASA's Jet Propulsion Laboratory, elected to the National Academy of Engineering in 2015.
Dave Limp
Dave Limp (David Limp) is an American technology executive and CEO of Jeff Bezos's space company Blue Origin since December 2023, after 13 years running Amazon's Devices and Services.
David R. Heebner
David R. Heebner (1927–2003) was an American defense systems engineer who made the towed sonar array practical, served in the Pentagon, and helped build SAIC.
David Scott
David Randolph Scott is a retired American Air Force colonel and NASA astronaut who commanded Apollo 15 in 1971 and became the seventh person to walk on the Moon.
DAVINCI
DAVINCI is a NASA Discovery Program mission to Venus with a descent sphere that will plunge through the atmosphere to the surface, selected in 2021.
Dawn (spacecraft)
Dawn was a NASA Discovery Program spacecraft that used ion propulsion to orbit Vesta and Ceres between 2011 and 2018, the first to orbit a dwarf planet.
Dawn-dusk orbit
A dawn-dusk orbit is a sun-synchronous orbit that stays aligned with the day-night terminator, so the satellite crosses the equator around 6 a.m. or 6 p.m. in perpetual sunrise or sunset.
DD Free Dish
DD Free Dish, launched as DD Direct+ in December 2004 and renamed in 2013, is India's only free-to-air DTH satellite TV service, operated by Doordarshan under Prasar Bharati.
De Laval nozzle
The de Laval nozzle, also called the convergent-divergent nozzle, is a tube that accelerates pressurized gas to supersonic speed, used in rocket engines and steam turbines.
Deep Impact (spacecraft)
Deep Impact was a NASA spacecraft that deliberately struck comet Tempel 1 on July 4, 2005, the first impact with a comet's nucleus, and later flew by Hartley 2.
Deep Space 1
Deep Space 1 was a NASA spacecraft launched in 1998 as the first New Millennium Program mission, testing ion propulsion and flying by asteroid Braille and comet Borrelly.
Deep Space Network
The Deep Space Network (DSN) is NASA's worldwide array of radio antennas for communicating with interplanetary spacecraft, managed by JPL and organized at three complexes: Goldstone, Madrid, and Canberra.
Deep-space optical communications
Deep-space optical communications is the use of near-infrared laser links, instead of radio, to send data between deep-space spacecraft and Earth, promising 10 to 100 times the data return for similar mass and power.
Defense Meteorological Satellite Program
The Defense Meteorological Satellite Program (DMSP) is a United States military series of polar-orbiting weather satellites that has supported Department of Defense operations since 1962.
Defense Support Program
The Defense Support Program is an American satellite constellation using infrared sensors in geosynchronous orbit to give early warning of ballistic missile launches, first launched in 1970.
Deke Slayton
Deke Slayton, born Donald Kent Slayton, was an American Mercury astronaut grounded for a heart condition who assigned crews and flew on Apollo-Soyuz in 1975.
Delta 2914
The Delta 2914 was an American three-stage expendable launch vehicle built by McDonnell Douglas that flew 30 missions from 1974 to 1979, mostly carrying communications and weather satellites toward geosynchronous transfer orbit.
Delta 7420-10C
The Delta 7420-10C was a two-stage variant of the American Delta II rocket with four solid boosters, flown 14 times between 1998 and 2018, all successfully.
Delta 7920-10C
Delta 7920-10C, also written Delta II 7920-10C, was a two-stage American expendable rocket of the Delta II family that made 17 successful launches between 1997 and its retirement in 2011.