EM 1110-2-2907
1 October 2003
Skylab
U.S. Earth-orbiting workshop that housed three crews of three
astronauts in 1973 and 1974.
Skylight
Component of light that is strongly scattered by the atmosphere and
consists predominantly of shorter wavelengths.
Slant range
In radar, an imaginary line running between the antenna and the target.
Slant-range distance
Distance measured along the slant range.
Slant-range distortion
Geometric distortion of a slant-range image.
Slant-range image
In radar, an image in which objects are located at positions
corresponding to their slant-range distances from the aircraft path. On
slant-range images, the scale in the range direction is compressed in
the near-range region
SLAR
Side-looking airborne radar.
SMIRR
Shuttle Multispectral Infrared Radiometer, a non-imaging
spectroradiometer carried by the NASA Space Shuttle covering ten
narrow wavebands in the 0.5-2.4 m range.
SMMR
Scanning Multichannel Microwave Radiometer, carried by Nimbus-7.
Smooth criterion
In radar, the relationship between surface roughness, depression
angle, and wavelength that determines whether a surface will scatter
the incident radar pulse in a smooth or intermediate fashion.
Software
Programs that control computer operations.
Sonar
Acronym for sound navigation ranging. Sonar is an active form of
remote sensing that employs sonic energy to image the seafloor.
Space Shuttle
U.S. manned satellite program in the 1980s, officially called the Space
Transportation System (STS).
Space Station
A planned series of three polar-orbiting, sun-synchronous satellites to
be launched by NASA, the European Space Agency, and the Japanese
Space Agency in the 1990s. They will carry a large range of remote-
sensing devices.
Spatial-frequency filtering
The analysis of the spatial variations in DN of an image and the
separation or suppression of selected frequency ranges.
Specific heat
The ratio of the heat capacity of unit mass of a material to the heat
capacity of unit mass of water.
Spectral hue
A hue that is present in the spectral range of white light and is analyzed
by a prism or diffraction grating.
Spectral reflectance
Reflectance of electromagnetic energy at specified wavelength
intervals.
Spectral sensitivity
Response, or sensitivity, of a film or detector to radiation in different
spectral regions.
Spectral vegetation index
An index of relative amount and vigor of vegetation. The index is
calculated from two spectral bands of AVHRR imagery.
Spectrometer
Device for measuring intensity of radiation absorbed or reflected by a
materiel as a function of wavelength.
Spectroradiometer
A device that measures the energy reflected or radiated by materials in
narrow EM wavebands.
Spectrum
Continuous sequence of electromagnetic energy arranged according to
wavelength or frequency.
Specular
Refers to a surface that is smooth with respect to the wavelength of
incident energy.
SPOT
Systeme Probatoire d'Observation del la Terre. Unmanned French
remote sensing satellite orbiting in the late 1980s.
Stefan-Boltzmann
5.68 x 10 -12 W . Cm-2 .K-4.
constant
Stefan-Boltzmann law
States that radiant flux of a blackbody is equal to the temperature to the
fourth power times the Stefan-Boltzmann constant.
Stereo base
Distance between a pair of correlative points on a stereo pair that are
oriented for stereo viewing.
Glossary-27
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