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  • 1
    facet.materialart.
    Unknown
    Development of an airborne laser bathymeter (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An airborne laser depth sounding system was built and taken through a complete series of field tests. Two green laser sources were tried: a pulsed neon laser at 540 nm and a frequency-doubled Nd:YAG transmitter at 532 nm. To obtain a depth resolution of better than 20 cm, the pulses had a duration of 5 to 7 nanoseconds and could be fired up to at rates of 50 pulses per second. In the receiver, the signal was detected by a photomultiplier tube connected to a 28 cm diameter Cassegrainian telescope that was aimed vertically downward. Oscilloscopic traces of the signal reflected from the sea surface and the ocean floor could either be recorded by a movie camera on 35 mm film or digitized into 500 discrete channels of information and stored on magnetic tape, from which depth information could be extracted. An aerial color movie camera recorded the geographic footprint while a boat crew of oceanographers measured depth and other relevant water parameters. About two hundred hours of flight time on the NASA C-54 airplane in the area of Chincoteague, Virginia, the Chesapeake Bay, and in Key West, Florida, have yielded information on the actual operating conditions of such a system and helped to optimize the design. One can predict the maximum depth attainable in a mission by measuring the effective attenuation coefficient in flight. This quantity is four times smaller than the usual narrow beam attenuation coefficient. Several square miles of a varied underwater landscape were also mapped.
    Keywords: OCEANOGRAPHY
    Type: NASA-TN-D-8079
    Format: application/pdf
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    Airborne laser bathymeter (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A description is given of a program concerned with the development and the evaluation of techniques for the measurement of water depth with a pulsed laser. Airborne laser bathymetry makes use of a light pulse which is sent downward. Information concerning the water depth is provided by the time interval observed between the arrival of the light pulse reflected from the water surface and the arrival of the pulse coming from the ocean floor. Details concerning the instrumentation used for the developed measurement method are discussed. Attention is also given to field experiments and aspects of system performance.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Electro-optical Systems Design Conference and International Laser Exposition; Nov 11, 1975 - Nov 13, 1975; Anaheim, CA
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
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