- 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.
The solid angle through which an instrument is sensitive to radiation. See instantaneous field of view, and resolution.
Industry:Aerospace
The square root of the variance. The value is expressed in the units of measure in which the observations were taken.
Industry:Aerospace
The time of a forward or reverse scan on an imager such as TM or ETM+. In order to make the geometric calibration easier, there is an active scan time (AST) and a turn-around time (TAT) for each scan. The Scan-Line-Corrector rotates two mirrors on the optical axis to keep the scan nearly perpendicular to the path of the satellite on the ground. The active scan time (AST) is controlled as long as the scanner is in the Scan-Angle-Monitor (SAM) mode, rather than the bumper mode.
At a Landsat satellite altitude of 705 Km, an active scan of about 6320 pixels covers approximately 189 Km on the ground and is cropped so that all the bands cover a common swath width of about 180 Km. Each scan on a TM is a little less than 0.5 Km wide. It is the knowledge of the AST and first and second half scan errors on each scan that allows the TM sensors to be systematically corrected when resampled such that only correction in rotation and translation need to be made for the image as a whole from ground control points. While in the SAM mode the wear on the bumpers results in increases in TAT but no change in AST. After twenty years in orbit, Landsat 5 TM lost its ability to stay in the SAM mode and had to be operated in the bumper mode. Also see bumper mode and geometric image calibration.
Industry:Aerospace
The transformation of image data, such as Landsat data, to match spatial relationships as they are on the Earth. Includes correction for band-to-band offsets, line length, Earth rotation, and detector-to-detector sampling delay. For Landsat, a distinction is made between data that have been geometrically corrected using systematic, or predicted, values (Level-1G) and data that have been geometrically corrected using more precise ground control point data (orthorectified, Level-1G-Terrain).
Industry:Aerospace
The translation-rotation rectification alignment process by which two images of like geometries and of the same set of objects are positioned coincident with respect to one another so that corresponding elements of the same ground area appear in the same place on the registered image. In this manner, the corresponding grey shades of the two images at any (x, y) coordinate or resolution cell will represent the sensor output for the some object over the full image frame being registered. In digital registration, the digital grids also must be superimposed at the same time the ground elements are superimposed.
Industry:Aerospace
The vertical projection of the actual flight path of an aerial or space vehicle onto the surface of the Earth.
Industry:Aerospace
The width, expressed either in wavelength or frequency, of a particular portion of the electromagnetic spectrum. A given sensor, such as radiometer detector or camera film, may be designed to measure or be sensitive to energy from a particular spectral interval. Also termed spectral band.
Industry:Aerospace
Time in which the recording of an event is simultaneous with the event. The real time of a satellite is that in which it simultaneously reports on its environment as it encounters it.
Industry:Aerospace
To vary, or control, the frequency, phase, or amplitude of an electromagnetic wave or other variable.
Industry:Aerospace
Variation in light intensity from maximum to minimum. This generally refers to a subject to be imaged or photographed.
Industry:Aerospace
