Glossary

S

s second

SABER Situational Awareness Beacon with Reply (system) (Navy)

SAMPEX Solar, Anomalous, and Magnetospheric Particle Explorer

SAO Smithsonian Astrophysical Observatory

SAR Synthetic Aperture Radar

Sarsat Search and Rescue Satellite-Aided Tracking System

SBUV Solar Backscatter Ultraviolet (spectral radiometer)

scramjet Supersonic-combustion ramjet

SDIO Strategic Defense Initiative Organization; see BMDO

SLS Spacelab Life Sciences (payload)

SLV Space Launch Vehicle

solar flare A sudden, intense brightening of a portion of the Sun's surface, often near a sunspot group; these flares, enormous eruptions of energy that leap millions of miles from the Sun's surface, pose a potential radiation hazard to humans in space

solar maximum The period in the roughly 11-year cycle of solar activity when the maximum number of sunspots is present

solar wind A stream of particles accelerated by the heat of the solar corona (outer region of the Sun) to velocities great enough to permit them to escape from the Sun's gravitational field

SPARTAN Shuttle Pointed Autonomous Research Tool for Astronomy

SPAS Shuttle Pallet Satellite

SPOT Satellite Pour l'Observation de la Terre (French satellite for the observation of the Earth)

squitter Transmitter for aircraft navigation and traffic control signals

SR&QA Safety, reliability, and quality assurance

SRL Space Radar Laboratory

SSBUV Shuttle Solar Backscatter Ultraviolet (spectrometer)

SSCE Solid Surface Combustion Experiment

SSME Space Shuttle Main Engine

SSTO Single-stage-to-orbit

STAC (Russian) Science and Technical Advisory Council

stall A loss of lift by an aircraft or airfoil resulting from insufficient air speed or excessive angle of attack

START Strategic Arms Reduction Treaty

STEP Space Test Experiments Platform

Stirling engine or generator One in which work is performed by the expansion of gas at high temperature to which heat is supplied through a wall

STOL Short Takeoff and Landing

STOVL Short Takeoff and Vertical Landing (aircraft)

stratosphere The atmospheric zone 12 to 31 miles (20 to 50 kilometers) up, exhibiting increased temperature with increased altitude

STRV Spsce Technology Research Vehicle

STS Space Transportation System

STSC Scientific and Technical Subcommittee (of COPUOS)

sunspot A vortex of gas on the surface of the Sun associated with stray local magnetic activity

super high frequency Any frequency between 3,000 and 30,000 megacycles per second

supernova An exceptionally bright nova (a variable star whose brightness changes suddenly) that exhibits a luminosity ranging from 10 million to 100 million times that of our Sun