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).

Satellite - Any body, natural or artificial, in orbit around a planet. The term is used most often to describe moons and spacecraft. A man-made satellite is a spacecraft that orbits another body, such as a planet or the Sun. A natural satellite is another term for a moon.

Saturation - The intensity of a color. A highly saturated color is a vivid, brilliant color; to dull a color (decrease its saturation), you add small amounts of its complement, making it closer to gray.

Scan - An image data line produced from a single detector of a band during a scan.

Scan Line - A series of spacecraft pointings in one dimension.

Scanning Mirror - Landsat TM’s scanning mirror collects data on both the forward and reverse scans.

Scenes - Each Landsat image collected is a scene. Each Landsat scene is 115 x 106 miles long. The globe is divided into 57,784 scenes, and each Landsat scene has about 3 billion bytes of data.

Single Event Upsets - A Single Event Upset (SEU) occurs when an energetic particle travels through a transistor substrate and causes electrical signals within the transistor.  This is a known phenomenon that usually occurs in near-earth orbit to spacecraft passing through the Van Allen belts, especially the northern and southern auroral zones and the south Atlantic anomaly. 

Site - The physical location of an International Ground Station (IGS) or the Mission Operations Center (MOC).

Spatial Data - Any information about the location, shape of, and relationships among geographic features. This includes remotely sensed data as well as map data.

Spatial Resolution - The area on the ground that an imaging system (such as a satellite sensor) can distinguish.

Spectral Range - The wavelength difference between two wavelengths in adjacent orders at the same angle of diffraction

Spectral Response - The relative amplitude of the response of a detector vs. the frequency of incident electromagnetic radiation.

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.

Subinterval - A segment of a raw wideband data interval received during a Landsat 7 contact period. Subintervals are caused by breaks in the wideband data stream due to communication dropouts and/or the inability of the spacecraft to transmit a complete observation (interval) within a single Landsat 7 contact period. The largest possible subinterval can be as long as a full imaging interval (a set of contiguous WRS scenes) transmitted during an uninterrupted contact period. The smallest possible subinterval can be as small as a set of a few contiguous ETM+ scans (a partial WRS scene). The smallest size of a subinterval is an operator modifiable parameter in LPS. If the smallest subinterval size is chosen to be as long as a full WRS scene, it will contain approximately 24 seconds worth of ETM+ data or 335 scans (without the 20 overlapping scans each

Sun-synchronous orbit - An orbit in which a satellite is always in the same position with respect to the rotating Earth at the same time of day. The satellite travels around the Earth in the same direction, at an altitude of approximately 438 miles (705 kilometers). Landsat-7 is sun-synchronous, always passing overhead at approximately 10:00 am local time.

Synchronous - The instantaneous alignment of two or more events in time. Events may occur at irregular intervals