LVIS
type: Concept
change note: 2015-06-18 12:14:26.0 [aaleman] revised long name per NSIDC request update AltLabel (Land, Vegetation, and Ice Sensor);
definition: SYSTEM OVERVIEW LVIS is a pulsed laser altimeter and measures range by timing a short (<10 ns duration) pulse of laser light between the instrument and the target surface. The entire time history of the outgoing and return laser pulses is digitized using a single detector, digitizer and timing clock. This configuration unambiguously describes the range to the surface as well as the vertical distribution of surfaces within each laser footprint. The LVIS system operates at altitudes up to 10 km AGL and has a 12 degree potential field-of-view (PFOV) within which footprints can be randomly spaced across track. Scanning is performed using galvanometer-driven scan mirrors that control the pointing of both the laser and the telescope instantaneous field-of-view (FOV). Scan mirrors are positioned in a stepped pattern, stopping to fire the laser and integrate the return signal at each beam location. This raster scan pattern efficiently covers 100% of the area within the data swath. Footprint sizes from 1 to 80 m are possible, determined by the AGL altitude of the airplane and the focal length of a diverging lens in the output path. The dual axis transmit scanner allows the swath pattern to remove forward motion of the aircraft from the collection pattern. Roll compensation has also been incorporated into the software for keeping collection directly below the aircraft. OPTICAL SYSTEM The receiver system consists of a 200-mm diameter, 5-power telescope with a 25-mm exit pupil. The telescope has a 200-mm aperture, f/2 Petzval1(1 Petzval lens: a high speed, narrow FOV lens composed of two achromatic lenses positioned about an aperture stop; named after the Austrian optician Josef Petzvald) objective with a 400-mm focal length directing light through a 50-mm focal length f/1.8 eyepiece, which produces a 25-mm collimated beam. A scan mirror, located at the exit pupil of the telescope, directs the beam through a 10-nm bandpass filter and onto a 25-mm molded aspheric condenser lens …
in scheme: instruments

Lidar/Laser Altimeters
type: Concept