Engineering topics
Publications and source records attributed to Freeman, A..
The JERS-1 Amazon Multi-season Mapping Study (JAMMS), part of the Global Rain Forest Mapping (GRFM) project led by the National Space Development Agency of Japan (NASDA), had an ambitious agenda to completely map the Amazon River floodpain (and surrounding areas) twice at high resolution.
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In this paper, an approach is described, which involves the fit of a combination of two simple scattering mechanisms to polarimetric SAR observations.
A design constraint traceable to the early days of spaceborne Synthetic Aperture Radar (SAR) is known as teh minimum antenna area constraint for SAR.
This paper will focus on our analysis of the imaging radar data in support of archaeological studies and subsequent ground verification of some of the features visible in the radar data.
This article describes past and current achievements in the development of space-borne imaging radar technology and discusses possibilities for the future. The article focuses on space-borne capabilities for civil and scientific purposes.
In the paper, a methodology, example, and accuracy assessment are given for a continental scale mosaic of the Amazon River basin at 100 m resolution using the JERS-1 satellite.
A design constraint traceable to the early days of spaceborne Synthetic Aperture Radar (SAR) is known as the minimum antenna area constraint for SAR. It specifies, as the name suggests, a minimum area for SAR antennas, to optimize performance.
The Earth-orbiting radar missions are planned for the near future by NASA - Shuttle Radar Topography Mission (SRTM) and LightSar.
A design constraint traceable ot the early days of spaceborne Synthetic Aperture Radar (SAR) is known as the minimum antenna area constraint for SAR. In this paper, it is confirmed that this constraint strictly applies only to the case where both the best possible resolution and the widest possible swath are the design goals. SAR antennas with area smaller than the constraint allows are shown to be possible, have been used on spaceborne SAR missions in the past, and should permit further, lower-cost SAR mission in the future.
Classification, decomposition and modeling of polarimetric SAR data has received a great deal of attention in the recent literature. The objective behind these efforts is to better understand the scattering mechanisms which give rise to the polarimetric signatures seen in SAR image data. In this Paper an approach is described, which involves the fit of a combination of two simple scattering mechanisms to polarimetric SAR observations. The mechanisms am canopy scatter from a cloud of randomly oriented oblate spheroids, and a ground scatter term, which can represent double-bounce scatter from a pair of orthogonal surfaces with different dielectric constants or Bragg scatter from a moderately rough surface, seen through a layer of vertically oriented scatterers. An advantage of this model fit approach is that the scattering contributions from the two basic scattering mechanisms can be estimated for clusters of pixels in polarimetric SAR images. The solution involves the estimation of four parameters from four separate equations. The model fit can be applied to polarimetric AIRSAR data at C-, L- and P-Band.
The effect of Faraday rotation on linearly polarized backscatter measurements from space is addressed.
Two Earth-orbiting radar missions are planned in the near future by NASA - Shuttle Radar Topography Mapping (SRTM) and LightSAR.
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During last year's AIRSAR Pacific Rim Deployment, data were collected over Angkor in Cambodia. The temples of Angkor date the city to the 9th-13th century AD, but little is known of its prehistoric habitation.
The effect of Faraday rotation on spaceborne polarimetric SAR measurements is addressed. Single-polarized, dual-polarized and quad-polarized backscatter measurements subject to Faraday rotation are modeled.
In order to build a user community for future NASA imaging radar products and programs, outreach activities have been implemented by JPL. These include: education outreach, public awareness outreach, and outreach to areas of the scientific and applications community who are not traditional imaging radar users. A key component is the NASA/JPL Imaging Radar Home Page on the World Wide Web.
Regional mapping of the Amazon basin using imaging radar is described. Two 60-day periods of radar mapping will be conducted, one in 1995, and one in 1996. One period will view the low-water season, and the other will view during the high-flood season. The main objective of the JAMMS project is to generate a regional map showing inundation throughout the Amazon Basin by comparing the two data sets.