Glossary of Space Exploration Terminology

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
I
IAA
Indian Astronautical Association.
IAF
International Astronautical Federation (formally inaugurated 1951).
IC
Integrated Circuit.
ICBM
Inter-Continental Ballistic Missile (range >5,500 km).
ICO
Intermediate Circular Orbit.
IGY
International Geophysical Year (1957-58).
Impulse
The product of the average force acting on a body and the interval of time during which it acts, being a vector quantity equal to the change of momentum of the body during the same time interval.
IMU
Inertial Measurement Unit.
Inclination
The angular distance between a satellite's orbital plane and the equator of its primary.
Inertial guidance
An on-board system for launch vehicles and spacecraft where gyroscopes, accelerometers and other devices satisfy guidance requirements.
Inertial measurement unit
An on-board instrument system that measures the attitude of a spacecraft. It includes accelerometers and gyroscopes.
Inferior conjunction
Alignment of Earth, Sun, and an inferior planet on the same side of the Sun.
Inferior planets
Planets whose orbits are closer to the Sun than Earth's, i.e. Mercury and Venus. Also called inner planets.
Infrared
Electromagnetic radiation of wavelengths between 7500 A, the limit of the visible light spectrum at the red end, and centimetric radio waves.
Infrared radiometer
A telescope based instrument that measures the intensity of infrared energy radiated by the targets.
Injection angle
The angle at which a spacecraft's return trajectory intersects the Earth's atmosphere.
Injector
Typically, a perforated plate through which liquid fuel and oxidizer are injected into the combustion chamber at a controlled rate.
Intelsat
Organization of 105 countries (July 1980) owning or operating systems of satellites used by 144 countries and territories around the world for international communications, and by 16 countries for domestic communications.
Interferometer
Any of several optical, acoustic, or radio frequency instruments that use interference phenomena between a reference wave and an experimental wave or between two parts of an experimental wave to determine wavelengths and wave velocities, measure very small distances and thicknesses, and measure indices of refraction.
Interplanetary magnetic field
The weak magnetic field filling interplanetary space, with field lines usually connected to the Sun. The IMF is kept out of the Earth's magnetosphere, but the interaction of the two plays a major role in the flow of energy from the solar wind to the Earth's environment.
Interplanetary probe
Unmanned instrumented spacecraft capable of reaching the planets.
Interplanetary shock
The abrupt boundary formed at the front of a plasma cloud (e.g. from a coronal mass ejection) moving much faster than the rest of the solar wind, as it pushes its way through interplanetary space.
Interstallar probe
Unmanned instrumented spaceship with artificial intelligence capable of reaching the nearer stars.
Interstellar ark
Hypothetical space colony capable of transporting human intelligence to the stars.
Inverse-square law
The mathematical description of how the strength of some forces, including gravity, changes in inverse proportion to the square of the distance from the source.
Ion
An atom that has lost or acquired one or more electrons.
Ion engine
A rocket engine, the thrust of which is obtained by the electrostatic acceleration of ionized particles.
Ionization
Formation of electrically charged particles. Can be produced by high-energy radiation such as light or UV rays, or by collision of particles in thermal agitation.
Ionosphere
An atmospheric layer dominated by charged, or ionized, atoms that extends from about 38 to 400 miles above the Earth's surface.
IR
Infrared.
IRBM
Intermediate Range Ballistic Missile (range 2400-5,500 km).
IRFNA
Inhibited Red Fuming Nitric Acid; 85% HNO3 + <5% H2O + 6-15% NOX.
ISAS
Institute of Space and Aeronautical Science; University of Tokyo (Japan).
Isotropic
A property of a distribution of particles where the flux is constant over all directions.
Isp
Specific Impulse. Also abbreviated SI.
ISRO
Indian Space Research Organization.
IWFNA
Inhibited White Fuming Nitric Acid; 97.5% HNO3 + 2% H2O + <0.5% NOX.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Rocketry & Space Technology

Glossary courtesy of Robert Braeunig's
Rocketry & Space Technology website.