Tenuous Surface Layer on the Moon: Evidence Derived from Radar Observations

Hagfors, T.; Brockelman, Richard A.; Danforth, Haines H.; Hanson, L. B.; Hyde, G. M.

doi:10.1126/science.150.3700.1153

Cited by 41 publications

(20 citation statements)

References 5 publications

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“…In that experiment, the Moon was observed by transmitting circular polarized pulses, and two linear orthogonal polarized components were received. Hagfors et al [1965] observed differences between the two received components, which they described as ratios of amplitude transmission coefficients that varied with angle of incidence, as shown by the circles in Figures C4 and C5.…”

Section: B2 Summarymentioning

confidence: 98%

“…Appendix C shows that modeling of these subsurface specular scatterers produces radar echoes with the cos 1.5 () dependence like that observed at centimeter and meter wavelengths. Also, specular scattering from subsurface layers of crater ejecta creates the polarization differences observed by Hagfors et al [1965] when they illuminated the Moon with circular polarizations and observed echoes in perpendicular linear polarizations.…”

Section: Overview Of Lunar Radar Scatteringmentioning

confidence: 99%

“…Converting the ratio of echo powers in the horizontal and vertical polarizations to the amplitude ratio used by Hagfors et al [1965], we have…”

Section: B2 Summarymentioning

confidence: 99%

“…Figure C4. Modeled and observed differences between linear polarized waves for the lunar radar experiment performed by Hagfors et al [1965] assuming specular scattering from subsurface layers refracted through a regolith overburden. Circles are amplitude transmission ratios of Hagfors et al [1965, Figure 3].…”

Section: B2 Summarymentioning

confidence: 99%

“…[71] To further examine whether subsurface layers of crater ejecta could act as subsurface specular scatterers, we modeled the lunar radar observations of Hagfors et al [1965]. In that experiment, the Moon was observed by transmitting circular polarized pulses, and two linear orthogonal polarized components were received.…”

Section: B2 Summarymentioning

confidence: 99%

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Modeling radar scattering from icy lunar regoliths at 13 cm and 4 cm wavelengths

Thompson¹,

Ustinov²,

Heggy³

2011

J. Geophys. Res.

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[1] Two orbital synthetic aperture radars (SARs), the Chandrayaan-1 Mini-SAR (13 cm wavelength) and the Lunar Reconnaissance Orbiter (LRO) Mini-RF (13 and 4.2 cm wavelengths), have been imaging the lunar surface searching for ice deposits in the polar permanently shadowed areas. To understand the radar signatures of lunar polar ices, an empirical two-component model with parametric variations of the specular and diffuse components was developed and validated. This model estimates scattering differences associated with slopes, surface roughness, thin regolith over ice, and patches of ice. Lunar radar backscatter cross sections for the average surface for the Chandrayaan-1 and LRO instruments are estimated from the radar cross sections from the Moon at 3.8, 23, and 68 cm wavelengths measured in the 1960s at the Massachusetts Institute of Technology. This modeling predicts that enhanced diffuse scattering from near-surface ice can be separated from rocks if the scattering is characterized by both the high reflectivity and circular polarization ratios (CPRs) like those observed on Mercury, Mars, and the Galilean satellites. Scattering from near-surface ices covered by a thin regolith can be separated from rocks if the enhancement is twice the average or more. If, however, the lunar ice is dispersed throughout the regolith as ice-filling pores, then scattering differences might be too small to detect. Preliminary validation using LRO radar data for a few polar and midlatitude craters indicate that the observed CPRs are consistent with our models for different regolith ice and roughness conditions. Citation: Thompson, T. W., E. A. Ustinov, and E. Heggy (2011), Modeling radar scattering from icy lunar regoliths at 13 cm and 4 cm wavelengths,

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Section: B2 Summarymentioning

confidence: 98%

Section: Overview Of Lunar Radar Scatteringmentioning

confidence: 99%

“…Converting the ratio of echo powers in the horizontal and vertical polarizations to the amplitude ratio used by Hagfors et al [1965], we have…”

Section: B2 Summarymentioning

confidence: 99%

Section: B2 Summarymentioning

confidence: 99%

Section: B2 Summarymentioning

confidence: 99%

See 3 more Smart Citations

Modeling radar scattering from icy lunar regoliths at 13 cm and 4 cm wavelengths

Thompson¹,

Ustinov²,

Heggy³

2011

J. Geophys. Res.

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U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 2, Radio Propagation in Nonionized Media; Progress in Radio Propagation in Nonionized Media

Katz¹,

Ament²,

Atlas³

et al. 1966

Radio Science

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In 1965 there was a strong reawakening of interest in “angel” or clear‐air radar echoes. Atlas [1965] postulated that "dot" or point‐like angles were reflections from smooth, sharp boundaries at the apex of convective thermals. Focusing from the curved surface reduced the requirement on the index gradient to 1 N unit through 1 em; however, the requirement of smoothness to a fraction of a em over the first Fresnel zone is still severe and lacks experimental confirmation. Dot angel activity at night requires another explanation. Hardy, Atlas, and Glover [1966] and Deam and LaGrone [1965] conclude that dot angel characteristics are explainable only if the targets are insects. These conclusions stem from considerations of absolute cross section and wavelength dependence.

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A Study of the Depolarization of Lunar Radar Echoes

Hagfors

1967

Radio Science

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The radar backscattering characteristics of the lunar surface are examined in detail at a wavelength of 23 cm. The backscattered waves are studied both for circular and for linear polarization of the transmitted wave. Effects relating to the orientation of the local plane of incidence on the moon with respect to the polarization of transmitted or scattered waves are investigated. The experimental results appear to strongly support the hypothesis that the returns at oblique angles of incidence arise through single scattering from discrete objects, as opposed to the returns at near normal incidence which are dominated by quasi‐specular reflection.

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Tenuous Surface Layer on the Moon: Evidence Derived from Radar Observations

Cited by 41 publications

References 5 publications

Modeling radar scattering from icy lunar regoliths at 13 cm and 4 cm wavelengths

Modeling radar scattering from icy lunar regoliths at 13 cm and 4 cm wavelengths

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 2, Radio Propagation in Nonionized Media; Progress in Radio Propagation in Nonionized Media

A Study of the Depolarization of Lunar Radar Echoes

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