Glossary of Space Exploration Terminology

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S
S-band
A range of microwave radio frequencies in the neighborhood of 2 to 4 GHz, used for communicating with piloted space missions (~2 Ghz).
SAR
Synthetic Aperture Radar.
Satellite
Any body, natural or artificial, in orbit around a planet. The term is used most often to describe moons and spacecraft.
Saturn
Sixth planet from the Sun, a gas giant or Jovian planet.
SCADA
Supervisory Control And Data Acquisition.
Scan platform
An articulated, powered appendage to the spacecraft bus which points in commanded directions, allowing optical observations to be taken independently of the spacecraft's attitude.
Seismometer
A device for measuring movements of the ground.
Semi-major axis
Half the major axis of an ellipse. The mean distance of a planet or satellite from its primary.
Sensor
An electronic device for measuring or indicating a direction or movement.
SEP
Societe Europeene de Propulsion (France).
Sequencer
A mechanical or electrical device which may be set to initiate a series of events and to make events follow a sequence.
Service module
That part of a spacecraft which usually carries a maneuvering engine, thrusters, electrical supply, oxygen and other consumables external to the descent module. Discarded prior to reentry.
SETI
Search for Extra-Terrestrial Intelligence.
Sextant
An instrument that measures angular distances from fixed celestial objects.
Shepherd moon
Moon which gravitationally confines ring particles.
Sidereal time
Time relative to the stars other than the Sun.
Simulator
A device that mimics the operational conditions of equipment or vehicles.
SIS
Satellite Interceptor System.
SL
Sea Level.
SLBM
Submarine Launched Ballistic Missile.
Slug
The U.S. customary unit of mass defined as the mass which receives an acceleration of 1 foot per second per second when a force of 1 pound is applied to it.
SM
Service Module.
Solar
Of or pertaining to the Sun.
Solar array
See solar panel.
Solar cell
A cell that converts sunlight into electrical energy. The light falling on certain substances (e.g. a silicon cell) causes an electric current to flow.
Solar constant
The electromagnetic radiation from the Sun that falls on a unit area of surface normal to the line from the Sun, per unit time, outside the atmosphere, at one astronomical unit.
Solar flare
A sudden brightening in some part of the Sun, followed by the emission of jets of gas and a flood of ultra-violet radiation. The gale of protons which accompanies a flare can be very dangerous to astronauts.
Solar nebula
The large cloud of gas and dust from which the Sun and planets condensed 4.6 billion years ago.
Solar panel
An array of light-sensitive cells attached to a spacecraft and used to generate electrical power for the vehicle in space. Also called solar array.
Solar sensors
Light-sensitive diodes which indicate the direction of the Sun.
Solar wind
A current of charged particles that streams outward from the Sun.
Solid propellant
A rocket propellant in solid form; usually consisting of a mixture of fuel and oxidizer.
Solid rocket booster
A rocket, powered by solid propellants, used to launch spacecraft into orbit.
Sounding rocket
A research rocket used to obtain data from the upper atmosphere.
Space
The universe beyond Earth's atmosphere. The boundary at which the atmosphere ends and space begins is not sharp but starts at approximately 100 miles above Earth's surface.
Space colony
Hypothetical extra-terrestrial habitat, for hundreds, thousands or even millions of people, perhaps established on a moon or planet or as an artificial construction in free space.
Space debris
Man-made objects or parts thereof in space which do not serve any useful purpose.
Space platform
A large artificial satellite conceived as a habitable base in space with scientific, exploratory or military applications. A space station.
Space station
An orbiting spacecraft designed to support human activity for an extended time.
Space weather
The popular name for energy-releasing phenomena in the magnetosphere, associated with magnetic storms, substorms and shocks.
Spacecraft
A piloted or unpiloted vehicle designed for travel in space.
Spacecraft clock
A counter maintained by the command & data subsystem. It meters the passing of time during the life of the spacecraft, and regulates nearly all activity within the spacecraft systems.
SPADATS
Space Detection and Tracking System (USA).
SPASUR
Space Surveillance System (USA).
Specific impulse
Parameter for rating the performance of a rocket engine. Indicates how many pounds or kilograms of thrust are obtained by consumption of a pound or kilogram of propellant in one second.
Spectrometer
An optical instrument that splits the light received from an object into its component wavelengths by means of a diffraction grating; then measuring the amplitudes of the individual wavelengths.
Spectroscopy
The study of the production, measurement and interpretation of electromagnetic spectra.
Spectrum
A particular distribution of wavelengths and frequencies.
Spin stabilization
Spacecraft stabilization accomplished by rotating the spacecraft mass, thus using gyroscopic action as the stabilizing mechanism.
SRB
Solid Rocket Booster.
SRB propellant
Composite propellant used in the Space Shuttle Solid Rocket Boosters. Consists mainly of ammonium perchlorate as the oxidizer, powdered aluminum as the metallic fuel, and PBAN, polybutadiene-acrylic acid-acrylonitrile terpolymer, as the polymeric fuel binder. A small amount of iron oxide is added to increase the burning rate. The final product is a rubbery material not unlike a typewriter eraser.
SRBM
Short Range Ballistic Missile (<800 km.)
SRC
Science Research Council (UK).
SSO
Sun-Synchronous Orbit.
SSPO
Sun-Synchronous Polar Orbit.
Stage
An independently powered section of a rocket or spacecraft, often combined with others to form multistage vehicles.
Star
A self-luminous celestial body consisting of a mass of gas held together by its own gravity in which the energy generated by nuclear reactions in the interior is balanced by the outflow of energy to the surface, and the inward-directed gravitational forces are balanced by the outward-directed gas and radiation pressures.
Static firing
The firing of a rocket on a special test stand to measure thrust, etc.
Stratosphere
A division of the Earth's atmosphere extending from altitudes ranging 5-10 miles to 18-30 miles.
Sub-orbital
Not attaining orbit, i.e. a ballistic space shot.
Sub-satellite
A secondary object released from a parent satellite in orbit, e.g. an electronic "ferret" released by a reconnaissance satellite.
Subatomic particles
Fundamental components of matter such as electrons or protons.
Subcarrier
Modulation applied to a carrier which is itself modulated with information-carrying variations.
Sublimator
An exposed metal plate, located on the outside of a spacesuit, that functions as a cooling coil to control suit temperatures.
Sun sychronous orbit
A walking orbit whose orbital plan precesses with the same period as the planet's solar orbital period. In such an orbit, a satellite crosses periapsis at about the same local time every orbit.
Sunspot cycle
The recurring, eleven-year rise and fall in the number of sunspots.
Sunspots
Dark regions on the Sun which are the centers of large vortices and possess powerful magnetic fields. Maximum sunspot activity occurs in cycles with a period of about 11 years.
Superior conjunction
Alignment between Earth and a planet on the far side of the Sun.
Superior planets
Planets whose orbits are farther from the Sun than Earth's, i.e. Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Also called outer planets.
Supernova
A large dying star, the final collapse of which is a cataclysmic explosion, hurling its substance into space.
Surface penetrator
A probe designed to penetrate the surface of a body, surviving an impact of hundreds of g's, measuring and telemetering the properties of the penetrated surface.
Surface rover
A semi-autonomous roving vehicle deployed on the surface of a planet or other body, taking images and soil analyses for telemetering back to Earth.
Sustainer engine
An engine that maintains propulsion of a launch vehicle once it has discarded its boosters.
Synthetic aperture radar
A radar imaging instrument which provides a penetrating illumination of radio waves, and is capable of imaging surfaces covered by clouds and haze. SAR images are constructed of a matrix where lines of constant distance or range intersect with lines of constant Doppler shift.

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Rocketry & Space Technology

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