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Nodal precession
Nodal precession, also known as nodal regression, is the gradual rotation of an orbit's line of nodes due to gravitational perturbations, chiefly Earth's equatorial bulge. It enables sun-synchronous orbits.
Non-orbital rocketry
Non-orbital rocketry is rocketry that reaches high altitude or space on suborbital trajectories without achieving orbital speed. It spans model, mid-power, and professional sounding rockets.
Non-rocket spacelaunch
Non-rocket spacelaunch, also called non-rocket spaceflight, is the set of proposed methods for reaching orbit without rockets, such as space elevators, skyhooks, mass drivers, and air launch.
Non-terrestrial network
A non-terrestrial network (NTN) is a 3GPP-defined network using satellites or high-altitude platforms as base stations, extending 5G coverage to oceans, deserts, and disaster zones towers cannot reach.
Normalized difference vegetation index
The normalized difference vegetation index (NDVI) is a satellite-derived index that quantifies green vegetation density by combining near-infrared and red reflectance, used to monitor crop health, forests, and drought.
North Coast Rocketry
North Coast Rocketry is an American hobby rocket company founded in northeast Ohio in the mid-1980s, selling mid-power kits and motors, licensed to Estes in 1995 and revived after 2011.
North Korean space program
The North Korean space program (DPRK space program) is North Korea's satellite and launch-vehicle effort, which placed its first military reconnaissance satellite, Malligyong-1, in orbit in 2023.
Northrop Grumman Innovation Systems
Northrop Grumman Innovation Systems, formerly Orbital ATK, was a Northrop Grumman business sector created in 2018 and dissolved in 2020, known for the Antares rocket and Cygnus spacecraft.
Northrop Grumman Pegasus
The Northrop Grumman Pegasus, also known as the Pegasus XL, is an American three-stage, solid-propellant, winged orbital rocket carried aloft under an airplane, first reaching orbit in 1990.
Norwegian rocket incident
The Norwegian rocket incident, also called the Black Brant scare, was a 1995 nuclear false alarm in which Russia mistook a Norwegian scientific rocket for a missile attack.
Nova (NASA rocket)
Nova was a family of NASA super-heavy-lift rocket designs studied from 1959 to 1962 for direct flights to the Moon; no vehicle was ever built.
Novatel
NovAtel is a Calgary, Canada manufacturer of high-precision GNSS receivers and GNSS+INS systems, part of Hexagon since 2007, whose reference receivers anchor aviation ground networks in the USA, Japan, Europe, China, and India.
Nuclear electric rocket
A nuclear electric rocket, also called nuclear electric propulsion (NEP), is a spacecraft propulsion system in which a fission reactor generates electricity that powers ion or Hall thrusters.
Nuclear pulse propulsion
Nuclear pulse propulsion is a proposed spacecraft propulsion method in which small nuclear explosions behind a vehicle push a plate, developed as Project Orion from 1958 to 1965 and never flown.
Nuclear salt-water rocket
The nuclear salt-water rocket (NSWR) is a proposed rocket propulsion concept by Robert Zubrin in 1991, fissioning dissolved uranium salt for high thrust and specific impulse.
Nuclear thermal rocket
A nuclear thermal rocket is a rocket engine that uses a fission reactor instead of combustion to heat hydrogen, delivering high thrust at roughly twice chemical propellant efficiency.
NuSTAR
NuSTAR (Nuclear Spectroscopic Telescope Array) is a NASA Small Explorer X-ray space telescope launched in 2012 and the first in orbit to focus high-energy X-rays for imaging.
O'Neill cylinder
The O'Neill cylinder is a proposed rotating space habitat, conceived by Princeton physicist Gerard K. O'Neill in 1969, in which people live on the inner surface of spinning cylinders.
O3b Networks
O3b Networks, founded by Greg Wyler in 2007, was a satellite broadband company named for the "other 3 billion" without internet access, now fully owned by SES.
Oberth effect
The Oberth effect is the rocketry principle that a rocket burn produces more orbital energy when performed at high speed, at the periapsis of an orbit, than far away.
Oblik
Oblik (Облик), Soviet for "appearance," was the code name for the Zenit-8 satellite, a film-return photoreconnaissance and cartography spacecraft built by TsSKB in Kuibyshev and flown from 1984.
Observations and explorations of Venus
Observations and explorations of Venus, also called the exploration of Venus, include over 40 spacecraft missions launched since 1961 that revealed a volcanic surface beneath permanent clouds.
Oceansat
Oceansat is a series of Indian Earth-observation satellites dedicated to ocean applications, developed and operated by ISRO, comprising Oceansat-1, launched in 1999, Oceansat-2, and Oceansat-3, also known as EOS-06.
OCO-2
OCO-2 (Orbiting Carbon Observatory-2) is a NASA satellite launched July 2014 that measures atmospheric carbon dioxide by recording absorption of reflected sunlight in near-infrared bands.
OCO-3
OCO-3 (Orbiting Carbon Observatory-3) is a NASA spectrometer mounted on the International Space Station that measures atmospheric carbon dioxide and plant fluorescence, launched in 2019.
Odyssey (launch platform)
Odyssey, originally Ocean Odyssey, is a converted drilling rig that served as the Sea Launch floating launch pad on the equator from 1999 to 2014.
OGCh
OGCh (ОГЧ), the Soviet "orbital warhead" carried by the R-36O missile and known in the West as FOBS, could deorbit a thermonuclear weapon onto a target before completing one Earth orbit.
OHB SE
OHB SE is a publicly traded European aerospace and technology group in Bremen, Germany, employing about 4,000 people, known for the Galileo navigation satellites and the LISA mission.
Oko (Око) (satellite programme)
Oko (Око) was a Soviet and Russian missile early-warning satellite system that detected US ICBM launches by infrared sensing, operating from 1978 until its replacement after 2012.
OMOTENASHI
OMOTENASHI was a JAXA 6U CubeSat lunar lander launched on NASA's Artemis I in 2022; a communication failure prevented its planned semi-hard landing on the Moon.