Wide-Band Radar for Measuring Thickness of Sea Ice

A wide-band penetrating radar system for measuring the thickness of sea ice is under development. The need for this or a similar system arises as follows: Spatial and temporal variations in the thickness of sea ice are important indicators of heat fluxes between the ocean and atmosphere and, hence,...

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Main Authors: Gogineni, Prasad, Holt, M., Kanagaratnam, Pannir
Format: Other/Unknown Material
Language:unknown
Published: 2008
Subjects:
Online Access:http://hdl.handle.net/2060/20080047198
id ftnasantrs:oai:casi.ntrs.nasa.gov:20080047198
record_format openpolar
institution Open Polar
collection NASA Technical Reports Server (NTRS)
op_collection_id ftnasantrs
language unknown
topic Communications and Radar
spellingShingle Communications and Radar
Gogineni, Prasad
Holt, M.
Kanagaratnam, Pannir
Wide-Band Radar for Measuring Thickness of Sea Ice
topic_facet Communications and Radar
description A wide-band penetrating radar system for measuring the thickness of sea ice is under development. The need for this or a similar system arises as follows: Spatial and temporal variations in the thickness of sea ice are important indicators of heat fluxes between the ocean and atmosphere and, hence, are important indicators of climate change in polar regions. A remote-sensing system that could directly measure the thickness of sea ice over a wide thickness range from aboard an aircraft or satellite would be of great scientific value. Obtaining thickness measurements over a wide region at weekly or monthly time intervals would contribute significantly to understanding of changes in the spatial distribution and of the mass balance of sea ice. A prototype of the system was designed on the basis of computational simulations directed toward understanding what signal frequencies are needed to satisfy partly competing requirements to detect both bottom and top ice surfaces, obtain adequate penetration despite high attenuation in the lossy sea-ice medium, and obtain adequate resolution, all over a wide thickness range. The prototype of the system is of the frequency-modulation, continuous-wave (FM-CW) type. At a given time, the prototype functions in either of two frequency-band/operational-mode combinations that correspond to two thickness ranges: a lower-frequency (50 to 250 MHz) mode for measuring thickness greater than about 1 m, and a higher frequency (300 to 1,300 MHz) mode for measuring thickness less than about 1 m. The bandwidth in the higher-frequency (lesser-thickness) mode is adequate for a thickness resolution of 15 cm; the bandwidth in the lower-frequency (greater-thickness) mode is adequate for a thickness resolution of 75 cm. Although a thickness resolution of no more than 25 cm is desired for scientific purposes, the 75-cm resolution was deemed acceptable for the purpose of demonstrating feasibility. The prototype was constructed as a modified version of a 500-to-2,000-MHz FM-CW radar system developed previously for mapping near-surface internal layers of the Greenland ice sheet. The prototype included two sets of antennas: one for each frequency-band/mode. For Arctic and Antarctic field tests, the prototype was mounted on a sled that was towed across the ice. The Arctic field test was performed in the lower-frequency mode on ice ranging in thickness from 1 to 4 m. In the analysis of the results of the Arctic field test, a comparison of the radar-determined ice thicknesses with actual ice thicknesses yielded an overall mean difference of 14 cm and standard deviation of 30 cm. The Antarctic field test was performed in the higher-frequency mode; analysis of the results led to the conclusion that this mode is useful for measuring thicknesses between 0.5 and 1 m. Several modifications have been conceived for implementation in further development toward an improved practical system: The system would function in a single frequency-band/mode (100 to 1,200 MHz) that would afford a resolution of about 15 cm. There would be a single antenna system that would be optimized for the entire 100-to-1,000-MHz frequency band. To enable ice-thickness surveys over larger areas, the system would be made capable of operating aboard a low-flying aircraft that could be either piloted or robotic. Data-processing techniques to deconvolve the system response have been developed on the basis of impulse-response measurements over a calm ocean. Implementation of these techniques in the system would enable correction for imperfections of the system and would thereby increase the effective sensitivity of the system.
format Other/Unknown Material
author Gogineni, Prasad
Holt, M.
Kanagaratnam, Pannir
author_facet Gogineni, Prasad
Holt, M.
Kanagaratnam, Pannir
author_sort Gogineni, Prasad
title Wide-Band Radar for Measuring Thickness of Sea Ice
title_short Wide-Band Radar for Measuring Thickness of Sea Ice
title_full Wide-Band Radar for Measuring Thickness of Sea Ice
title_fullStr Wide-Band Radar for Measuring Thickness of Sea Ice
title_full_unstemmed Wide-Band Radar for Measuring Thickness of Sea Ice
title_sort wide-band radar for measuring thickness of sea ice
publishDate 2008
url http://hdl.handle.net/2060/20080047198
op_coverage Unclassified, Unlimited, Publicly available
geographic Antarctic
Arctic
Greenland
The Antarctic
geographic_facet Antarctic
Arctic
Greenland
The Antarctic
genre Antarc*
Antarctic
Arctic
Climate change
Greenland
Ice Sheet
Sea ice
genre_facet Antarc*
Antarctic
Arctic
Climate change
Greenland
Ice Sheet
Sea ice
op_source CASI
op_relation Document ID: 20080047198
http://hdl.handle.net/2060/20080047198
op_rights Copyright, Distribution as joint owner in the copyright
_version_ 1766255193723240448
spelling ftnasantrs:oai:casi.ntrs.nasa.gov:20080047198 2023-05-15T13:51:22+02:00 Wide-Band Radar for Measuring Thickness of Sea Ice Gogineni, Prasad Holt, M. Kanagaratnam, Pannir Unclassified, Unlimited, Publicly available November 2008 application/pdf http://hdl.handle.net/2060/20080047198 unknown Document ID: 20080047198 http://hdl.handle.net/2060/20080047198 Copyright, Distribution as joint owner in the copyright CASI Communications and Radar NPO-45565 NASA Tech Briefs, November 2008; 7-8 2008 ftnasantrs 2019-07-21T06:40:32Z A wide-band penetrating radar system for measuring the thickness of sea ice is under development. The need for this or a similar system arises as follows: Spatial and temporal variations in the thickness of sea ice are important indicators of heat fluxes between the ocean and atmosphere and, hence, are important indicators of climate change in polar regions. A remote-sensing system that could directly measure the thickness of sea ice over a wide thickness range from aboard an aircraft or satellite would be of great scientific value. Obtaining thickness measurements over a wide region at weekly or monthly time intervals would contribute significantly to understanding of changes in the spatial distribution and of the mass balance of sea ice. A prototype of the system was designed on the basis of computational simulations directed toward understanding what signal frequencies are needed to satisfy partly competing requirements to detect both bottom and top ice surfaces, obtain adequate penetration despite high attenuation in the lossy sea-ice medium, and obtain adequate resolution, all over a wide thickness range. The prototype of the system is of the frequency-modulation, continuous-wave (FM-CW) type. At a given time, the prototype functions in either of two frequency-band/operational-mode combinations that correspond to two thickness ranges: a lower-frequency (50 to 250 MHz) mode for measuring thickness greater than about 1 m, and a higher frequency (300 to 1,300 MHz) mode for measuring thickness less than about 1 m. The bandwidth in the higher-frequency (lesser-thickness) mode is adequate for a thickness resolution of 15 cm; the bandwidth in the lower-frequency (greater-thickness) mode is adequate for a thickness resolution of 75 cm. Although a thickness resolution of no more than 25 cm is desired for scientific purposes, the 75-cm resolution was deemed acceptable for the purpose of demonstrating feasibility. The prototype was constructed as a modified version of a 500-to-2,000-MHz FM-CW radar system developed previously for mapping near-surface internal layers of the Greenland ice sheet. The prototype included two sets of antennas: one for each frequency-band/mode. For Arctic and Antarctic field tests, the prototype was mounted on a sled that was towed across the ice. The Arctic field test was performed in the lower-frequency mode on ice ranging in thickness from 1 to 4 m. In the analysis of the results of the Arctic field test, a comparison of the radar-determined ice thicknesses with actual ice thicknesses yielded an overall mean difference of 14 cm and standard deviation of 30 cm. The Antarctic field test was performed in the higher-frequency mode; analysis of the results led to the conclusion that this mode is useful for measuring thicknesses between 0.5 and 1 m. Several modifications have been conceived for implementation in further development toward an improved practical system: The system would function in a single frequency-band/mode (100 to 1,200 MHz) that would afford a resolution of about 15 cm. There would be a single antenna system that would be optimized for the entire 100-to-1,000-MHz frequency band. To enable ice-thickness surveys over larger areas, the system would be made capable of operating aboard a low-flying aircraft that could be either piloted or robotic. Data-processing techniques to deconvolve the system response have been developed on the basis of impulse-response measurements over a calm ocean. Implementation of these techniques in the system would enable correction for imperfections of the system and would thereby increase the effective sensitivity of the system. Other/Unknown Material Antarc* Antarctic Arctic Climate change Greenland Ice Sheet Sea ice NASA Technical Reports Server (NTRS) Antarctic Arctic Greenland The Antarctic