A Strategy for Active Remote Sensing Amid Increased Demand for Radio Spectrum (2015) / Chapter Skim
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4 Active Earth Remote Sensing for Land Surface Applications
4 Active Earth Remote Sensing for Land Surface Applications
Pages 77-102
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From page 77... ...
Active microwave remote sensing has proven valuable across a number of science disciplines and practical applications, including geology, urban planning, agriculture and crop management, forestry and biomass assessment, hydrology and water resource management, weather forecasting, generation of topographic maps, sea ice mapping and glacier studies, earthquake and volcano studies, archaeological investigations, and post-disaster assessment. The unique capabilities and global coverage afforded by spaceborne radar are also making key contributions to understanding the mechanisms of longterm climate change and its impacts.
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From page 78... ...
Such signal characteristics can be used to obtain a number of important geophysical parameters, which are discussed in the next section. Different types of radar systems have been used to study the land surface.
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From page 79... ...
Although the primary focus of this section is the use of radar as a remote sens ing tool, it is also important to acknowledge the use of other active techniques that utilize the radio spectrum. Radio ranging between two orbiting satellites is used to precisely measure Earth's gravity field, as is the case with the joint U.S./German Gravity Recovery and Climate Experiment (GRACE)
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From page 80... ...
Table 4.1 provides a summary of the currently operating active sensor missions for land applications, and Table 4.2 provides a summary of future such missions. SCIENCE AND APPLICATIONS OF ACTIVE MICROWAVE REMOTE SENSING OF EARTH'S SURFACE The Solid Earth: Geology, Geophysics, and Seismology From the very beginning of the radar remote sensing era, the value of SAR images has been recognized in the field of solid Earth studies.1 Radar backscatter and polarimetry give insight into the nature of surface materials.
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From page 81... ...
d 5.4 GHz C-band May Using advanced C-band 5.25-5.57 GHz 2013 synthetic aperature radar to provide all-weather, day and-night images of Earth's surface; used to monitor ice loss from ice caps and ice sheets and used to map ground movements related to earthquakes.
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," http://global.jaxa.jp/projects/sat/ alos2/, accessed June 3, 2015. c Earth Observation Portal, "HJ-1 (Huan Jing-1: Environmental Protection & Disaster Monitoring Con stellation)
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(Dual C/Ku-band) altimeter mode for ocean surface topography, surface wind speed, surface wave height; and SAR mode for C-band imagery of Earth's surface (ESA)
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surface topography, surface wind speed, surface wave height; and SAR mode for Ku-band imagery of Earth's surface (ESA) Meteor-M SARn 9.6 GHz X-band 2015/ 2016 X-band SAR imagery for 9.3-9.9 GHz observing Earth's surface; monitoring ice fields (RSA)
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From page 85... ...
org/web/eoportal/satellite-missions/m/metop-sg, accessed June 4, 2015. j Earth Observation Portal, "PAZ SAR satellite mission of Spain," https://directory.eoportal.org/web/ eoportal/satellite-missions/p/paz, accessed June 4, 2015.
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. Although not a radar remote sensing technique, the use of differential GPS to precisely measure the motion of points on Earth is also critical to the field of seismology.
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SOURCE: NASA/JPL-Caltech/ASI/Google Earth, Image PIA18798: NASA Analyses of Global Positioning System Data and Italian Radar Satellite Data Reveal Napa Quake Ground Deformation.
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The difference in these heights is related to the overall 3 Government of Canada, Report on International GEO Workshop on Synthetic Aperture Radar (SAR) to Support Agricultural Monitoring, November 2-4, Alberta, Canada, 2010.
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ESA is planning the P-band BIOMASS satellite mission and NASA/ISRO is planning the L-band/S-band NISAR satellite mission. Both are currently planning for launch in 2020 and have global biomass estimation and ecosystem characterization as key science objectives.
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Consequently, active remote sens ing techniques from airborne or spaceborne platforms are a valuable and reliable means to measure water in its various forms over local, regional, or global scales. Soil Moisture Soil moisture measurements are used globally for a wide range of applications in hydrology, agriculture, climate monitoring, weather forecasting, and disaster mitigation (including risk forecasting of landslides and flood runoff)
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From page 91... ...
The rapid release of methane from such stores is thought to have serious additional global warming potential. As another example, the Argentine SAOCOM mission, to be launched in 2015, is an L-band polarimetric SAR for which one primary measurement is the regular production of high-resolution soil moisture maps in agricultural regions of significant national interest, such as the pampas.
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From page 92... ...
is also capable of determining the level of water bodies to an accuracy of cen timeters using interferometric techniques.8 The global mapping of surface water dynamics is one of the main objectives of the joint NASA/CNES Surface Water Ocean Topography (SWOT) mission sched uled for launch in 2020.
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From page 93... ...
Radar imagery from polarimetric SARs or scatterometers operating from the L-band to the Ku-band provide the ability to measure snow over a broad area. Radar sounders operating at the Ku-band have been able to measure snow depth and stratigraphy over ice sheets.10 In addition to being able to make all-weather measurements through clouds, microwave sensors are able to penetrate into the snow, and thus yield information about snow density, which is directly related to the amount of liquid water produced upon melting.
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From page 94... ...
addition to sensors already operating, the NRC Earth science decadal survey has called for the development of a dedicated space mission to address snow.11 The Cryosphere The cryosphere covers portions of Earth's surface where water is in solid form, including sea ice, ice sheets, and glaciers. Diminishing glaciers and sea ice are considered by scientists to be an early indicator of global warming.
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The 12 W Dierking, Sea ice monitoring by synthetic aperture radar, Oceanography 26(2)
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Finally, gravity field measurements made using satellite-to-satellite radio ranging can yield critical insight into the bulk mass dynamics associated with Earth's ice sheets. Topographic Mapping Accurate topographic maps of Earth's surface are essential to many terrestrial science investigations and civil applications.
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From page 97... ...
In vegetated areas, the UHF data can penetrate to near the surface to get ground-level topography, whereas the X-band sensor yields heights higher up in the canopy. Other Applications: Urban Planning, Disaster Management The availability of high-resolution SAR imagery has enabled advances in urban planning and land-use management efforts.
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From page 98... ...
Mouginot, and B Scheuchl, "MEaSUREs InSAR-Based Antarctica Ice Velocity Map," Sample Data Image, NASA DAAC, National Snow and Ice Data Center, Boulder, Colo., 2011, http://dx.doi.
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From page 99... ...
SPECTRUM ISSUES FOR MICROWAVE REMOTE SENSING OF THE LAND SURFACE For the broad variety of applications discussed in the earlier sections of this chapter, microwave remote sensing of the land surface requires the use of a wide range of frequencies. The HF, VHF, UHF, L-, S-, C-, X-, Ku-, and Ka-bands are all currently in use.
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From page 100... ...
• There is currently no HF or VHF spectrum allocation for Earth science remote sensing from space. This will be a region of intense interest for subsurface sounders in the future.
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From page 101... ...
Data from each country's pro grams are being used by other countries' scientists in order to address regional and global issues. Finding 4.2: Active microwave remote sensing of the land has proven valuable across a number of science disciplines and practical applications, including geology, urban planning, agriculture and crop management, forestry and biomass assess ment, hydrology and water resource management, weather forecasting, generation
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From page 102... ...
Special consideration should be given to accommodating these few but important low usage systems. Recommendation 4.3: The current frequency allocations for active remote sensing for land applications should be preserved and strongly protected to ensure their continued contribution to the nation and to scientists' understanding of Earth and its processes.
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