Microwave Dielectric Properties Of Rocks

Ulaby, F. T.; Bengal, T.; East, J.R.; Dobson, M.C.

doi:10.1109/igarss.1988.569528

Cited by 24 publications

(63 citation statements)

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“…Areas within the core area of the pahoehoe flows had values of e' from 4 to 5, while more dense a'a flow centers reached values of 7.35. We thus conclude that (1) differences in dielectric constant between and within the various lava flows are dominated by bulk density variations, consistent with other lab studies of basaUs [Ulaby et al, 1988]; (2) the upper few centimeters of many pahoehoe flows tend to be less dense than the inner core, leading to a slightly lower Fresnel reflection coefficient.…”

Section: Appendix: Measurement Of Tava Flow Dielectric Constantsupporting

confidence: 75%

Lava flow surface roughness and depolarized radar scattering

Campbell¹,

Shepard²

1996

J. Geophys. Res.

101

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Abstract. Surface roughness has a strong controlling influence on radar scattering and other types of remote sensing observations. We compare field measurements of surface topography and dielectric constant for a range of lava flow textures to aircraft multipolarization radar observations at 5.7. 24, and 68 cm (C, L, and P band) wavelengths. The roughness is found to vary with scale in a self-affine (fractal) manner for scale lengths between 25 cm (the smallest horizontal step size) and 3-5 m. This result is used to demonstrate that a two-component surface description, consisting of the fractal dimension and rms height or slope at some reference scale, can resolve some of the ambiguities in previous efforts to quantify roughness. At all three radar wavelengths, the HV backscatter cross section is found to vary in an approximately exponential fashion with the rms height or Allan deviation at some reference scale, up to a saturation point, where the surface appears entirely diffusely scattering to the radar. Based on these observations, we use a parameter, y, defined as the ratio of rms height to the particular scale of measurement. Backscatter values at 24-cm wavelength and the topographic profile data were used to derive expressions which link the HV radar cross section to 7 or to the analogous wavelength-scale rms slope. These equations provide a reasonable fit to 24-and 68-cm echoes and for rough surfaces at 5.7 cm, but yield poor results for 5.7-cm echoes on smooth terrain. We conclude that the roughness at the two larger scales is well described by a single fractal dimension and rms height, but that texture at very srnall scales is characterized by different statistics. This inference is supported by analysis of 5-cm horizontal spacing topographic profiles, 'i'he relationships defined here allow determination of the surface rms height or slope at the scale of the radar wavelength. Given radar data at additional wavelengths, a more complete view of the statistical properties of the surface can be developed. Such techniques may be useful in analyses of synthetic aperture radar images for terrestrial volcanic areas, Magellan data for Venus, and other planetary radar observations. Introductionsurface roughness and specific remote sensing properties for many types of observations remains elusive. In this paper, we Tlie topography of natura! surfaces at scales of a icw meters focus on the nature of roughness and its scale dependence for or less is commonly referred to as roughness. These variations terrestrial rwcky lava surfaces, and the effect of such changes in height and slope, their magnitude, and the changes in on depolarized radar backscatter at a variety of incidence structure as a function of scale length are of fundamental ai\gies and wavelengths. importance to the interpretation of geologic emplacement Analysis of radar scattering from natural surfaces has been mechanisms and subsequent modification. For most planetary of interest for over 30 years, and two distinct approaches have studies and many terr...

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Section: Appendix: Measurement Of Tava Flow Dielectric Constantsupporting

confidence: 75%

Lava flow surface roughness and depolarized radar scattering

Campbell¹,

Shepard²

1996

J. Geophys. Res.

101

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“…An excellent review of this model is contained in Barrick and Peake [1967], and the practical limitations on various implementations of the model are well covered in Ulaby et al [1987]. Since the model solution is based upon slight perturbations from a flat surface, rms heights on the scale of the radar wavelength are prohibited; this constraint also prevents a geometric optics approach to this scattering problem, which is possible for the large-scale roughness of the Hagfors/Kirchhoff models.…”

Section: The Small-perturbation Modelmentioning

confidence: 99%

“…It is also important to note that the first-order model always predicts HH/VV ratios less than or equal to unity. The first-order small-perturbation model is most commonly used, but it is possible to carry the expansion to higher orders [Ulaby et al, 1987;Barrick and Peake, 1967]. At second order, the model predicts an HV backscatter component, and can be used over a somewhat larger range of surface roughnesses.…”

Section: The Small-perturbation Modelmentioning

confidence: 99%

“…The lava is massive, with few vesicles or pore spaces, and there is no broken glass coating as is seen on many of the Hawaiian lava flows. The dielectric constant for this flow is thus taken to be 6-8 [Ulaby et al;, Figure 8 presents an L band HH AKSAR image of this flow. We did not use the C band data for this site, as there were questions about the validity of the antenna beam pattern correction.…”

Section: Spflowmentioning

confidence: 99%

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Radar polarization properties of volcanic and playa surfaces: Applications to terrestrial remote sensing and Venus data interpretation

Campbell¹,

Arvidson²,

Shepard³

1993

J. Geophys. Res.

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The radar polarization properties of lava flows in Hawaii (Kilauea) and Arizona (SP flow), and two playa suifaces (Lunar Lake. Nevada and Lavic Lake, California), are compared to the predicted bebaviors of theoretical scattering models. At 5,7 ctn and 24 cm wavelengths, Kilauea lava flows can be modeled by a combination of facet and diffuse (dipole-Iike) scattering. Scattering by rock foces on the scale of the radar wavelength is proposed to account for much of the facet letum. The tadar echoes at 24-cni wavelength íioia SP flow are. on average, consistent with entirely diffuse scattering, but there are regions within the flow where circular polarization ratios exceed unity, suggesting a coherent scattering effect 68 cm data for the lava flows show evidence of radar penetration and volume scattering. The playa surfaces are characterized by polarization properties which in some cases are qualitatively consistent with the first-order smallperturbation model, but the echoes do not closely match the predictions of this model for any reasonable dielectric constant value. These results show that it may be difficult to construct invertible models for the polarization behavior of some surfaces (the playas), whereas for others (the Kilauea lava flows) the scattering properties can be successfully modeled. The first-order small-petturiïation model is not aj^jnqiriate for inverse modeling of most terrestrial lava flows, though very smooth surfaces on Venus may be amenable to the use of this model. High circular polarization ratios observed for SP flow, tentatively attributed here to ccberent backscatter, may be analogous to Aiecibo observations of high'teflectivity areas on Venus. iNJTRODUCnONImaging radar systems are an important geologic remote sensing tool for terrestrial and planetary applications. The sensitivity of radar backscatter tneasuiements to roughness on cm to meter scales and to variations in bulle dielectric properties makes them useful for tnapping out differences in surface morphology, density, and reflectivity. Airborne and spacebome radar systems are in use and being developed which offer the possibility of rapid hi g h-resolution mapping of terrrestrial volcanic surface structure . For Venus, microwave remote sensing provides our only view of títe sircface on a global scale, so interpreting radar data is a crucial part of assembling a geologic frameworlc for this planet [Saunders et ai, 1992].A fundamental issue in radar remote sensing is the relationship between surface roughness and dielectric parameters and the intensity; polarization, and angular dependence of the backscattered wave. Over the past thirty years, several models for surface scattering have been widely used: the quasi-specular or physical optics model [Hagfors, 1964; PettengUl et al., 1988;Tyler et al., 1992], the smallperturbation approach [Barrick and Peake, 1967], coherent backscatter theory [Hapke, 1990], und "diffuse" scattering models [Ford and Senske, 1990], Aspects of these models were often discussed in analyses of terrestrial...

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“…Integrating over the distribution in small radius increments avoids difficulties with rapidly fluctuating resonant echoes, especially at lower loss tangent HanS = s"/s') values. We examined two cases that bracket a reasonable dielectric range for dry rocks (Ulaby et al 1988 matches the C-band echoes for dmax ~ 0.5 m, but greatly overestimates the L-and P-band values. The dashed line shows the backscatter for e' • 6, tana •0.01, which fits quite well in the range 24-68 cm.…”

Section: A Polarized Echoesmentioning

confidence: 99%

Radar Backscatter from Mars: Properties of Rock-Strewn Surfaces

Campbell¹

2001

Icarus

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Microwave Dielectric Properties Of Rocks

Cited by 24 publications

References 0 publications

Lava flow surface roughness and depolarized radar scattering

Lava flow surface roughness and depolarized radar scattering

Radar polarization properties of volcanic and playa surfaces: Applications to terrestrial remote sensing and Venus data interpretation

Radar Backscatter from Mars: Properties of Rock-Strewn Surfaces

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