- Industry: Aerospace
- Number of terms: 16933
- Number of blossaries: 2
- Company Profile:
The Executive Branch agency of the United States government, responsible for the nation's civilian space program and aeronautics and aerospace research.
Representation of data in the form of discrete bits, or equal integral units. Contrast to analog.
Industry:Aerospace
Satellite scanners operating in backup bumper mode. Landsat-type sensors such as the Thematic Mapper (TM) and the Enhanced Thematic Mapper Plus (ETM+) are designed to have a fixed line length on every scan controlled by the Scan Angle Monitor (SAM). When the wear on the bumpers is sufficiently large that it is no longer possible to maintain control in the SAM-mode, then the instrument can be put in a backup bumper mode where the mirror is allowed to scan at a fixed frequency of 14 Hz as a free pendulum rather than being controlled on each scan. The calibration shutter is still synchronized with the scan mirror in this mode so that calibration pulse can be obtained at the end of each scan. However, the variability of the scan length increases in bumper mode. The Landsat 5 TM was placed in the bumper mode in 2002. Also see scan line length. .
Industry:Aerospace
Short for "radio detection and ranging," radar sends out short pulses of microwave energy and records the returned signal's strength and time of arrival.
Industry:Aerospace
Small rapid variations in a variable (such as a waveform) due to deliberate or accidental electrical or mechanical disturbances or to changes in the supply voltages in the characteristics of components, etc. Jitter effects arising from the oscillating mirrors and other movable components aboard Landsat are often a cause of certain anomalies in the image data received and must be compensated for by the ground processing system.
Industry:Aerospace
Sometimes expressed using the obsolete term micron, a micrometer is one-millionth of a meter and also can be expressed as 10 -6 meter, one thousandth of a millimeter, one 25-thousandth of an inch.
Industry:Aerospace
Square, rectangular, or, more rarely, hexagonal lattice for recording geographical data, The simpler grids are usually not related to geodetic coordinate systems.
Industry:Aerospace
Supporting data collected on the ground, and information derived therefrom, as an aid to the interpretation of remotely sensed data. Ground data typically pertain to weather, soils, and vegetation types and conditions.
Industry:Aerospace
Systematic periodic noise in image or calibration data which can be characterized in terms of frequency, phase and amplitude. It is often quantified using Fourier analysis. Coherent noise is usually electronic, coming from sources such as power supplies, transmitters, and clocks. It is desirable to remove, isolate or characterize sources of instrumental coherent noise before launch. It is possible to characterize signal-independent coherent noise most easily on dark background data such as night scenes. It is also visible in dark radiometrically homogeneous regions of a scene such as water. If the coherent noise is well enough characterized and stable with time then it can be significantly reduced with notch filtering using inverse Fourier transforms as a part of radiometric processing to produce the user’s product on the ground. Also see noise.
Industry:Aerospace
That point on the celestial sphere vertically below the observer (i.e. the point on the Earth directly below an orbiting satellite), or 180° from the zenith.
Industry:Aerospace
