Remote sensing of the Moon's subsurface with multifrequency microwave radiometers: A numerical study

Montopoli, Mario; Carlofelice, Alessandro Di; Tognolatti, P.; Marzano, Frank S.

doi:10.1029/2009rs004311

Cited by 30 publications

(16 citation statements)

References 24 publications

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“…Figure illustrates the weighting functions of four channels calculated by equation with new loss tangent form. Figure shows the diurnal shape of modeled equatorial highlands T B as compared to 19.35‐ and 37‐GHz MRM data, which provide a tighter fit than but also fall within the range of other recently published lunar loss tangent models (Fa & Wieczorek, ; Montopoli et al, ). Changes in the loss tangent will affect both the mean and diurnal amplitude of the brightness temperature; therefore, the strong match to the observed amplitudes both the 37‐ and 19.35‐GHz channels implies that these data are in fact well calibrated.…”

Section: Approach and Methodssupporting

confidence: 76%

New Constraints on Thermal and Dielectric Properties of Lunar Regolith from LRO Diviner and CE‐2 Microwave Radiometer

2020

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We derive a new constraint on the thermal and dielectric properties of the lunar regolith layer by reconciling data from the Lunar Reconnaissance Orbiter (LRO) Diviner infrared radiometer and Chang'E-2 (CE-2) microwave radiometer (MRM). The bolometric Bond albedo of the lunar surface, which characterizes the ability of the lunar surface to reflect visible radiation, is a function of incidence angle. We determined the Bond albedo by using the Lunar Orbiter Laser Altimeter 1,064-nm normal albedo and the surface temperature at noon as a function of latitude. The results suggest a modification to existing regolith thermal conductivity models based on a fit to the diurnal variation of Diviner data. Based on the thermal model, a 1-D radiative transfer and dielectric properties model is developed to fit MRM data for the global Moon. With a new dielectric loss tangent equation for highland regolith applied, our model matches MRM data well at 19.35 and 37 GHz, which are generally accepted to be well calibrated. A global map of loss tangent of the Moon at these frequencies is also obtained by fitting the diurnal amplitude of microwave brightness temperature (T B ) of each location on the Moon. We find that the loss tangent of highlands regolith has a slight frequency dependence and is larger than previous studies. We also identify a large discrepancy between our theoretical model and T B obtained by CE-2 MRM at low frequencies, which is attributed to issues caused by contamination on calibration horn. Plain Language SummaryWe derive the physical properties of the dusty layer on the surface of the Moon by using the data from Lunar Reconnaissance Orbiter Diviner infrared radiometer, Lunar Orbiter Laser Altimeter, and Chang'E-2 microwave radiometer. Our results show that visible radiation reflected by the Moon surface is a function of incidence angle. The dusty layer is much less transparent at microwave band as we expected before. The dielectric properties of the layer vary a lot from bright highlands to dark Maria, which can be used to distinguish different compositions. We also recognize some calibration errors within the microwave radiometer data set.

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Section: Approach and Methodssupporting

confidence: 76%

New Constraints on Thermal and Dielectric Properties of Lunar Regolith from LRO Diviner and CE‐2 Microwave Radiometer

2020

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“…The microwave emissivity ( e ) of the surface can be simplified to (Pabari, )

e = 1 - r = 1 - {(||, \frac{1 - \sqrt{ε}}{1 + \sqrt{ε}})}^{2},

where r is the Fresnel power reflection coefficient for normal incidence. Since the regolith can be considered to consist of discrete layers (Montopoli et al, ) of smaller size, T B can be simulated for MRM's nadir observing conditions as

T_{B} false(ν, t false) = e \cdot true \int_{0}^{\infty} κ_{α} false(ν, z false) T false(t, z false) e^{- true \int_{0}^{z} κ_{α} false(ν, z^{'} false) normald z^{'}} normald z,

where κ α ( ν , z ) is the depth‐dependent power absorption coefficient,

κ_{α} false(ν, z false) = false(2 π ν false/ c false) \sqrt{ε^{'} false(z false)} \tan δ

, ν is the frequency,

\tan δ = ε^{''} false(z false) false/ ε^{'} false(z false)

is the loss tangent of the material, and ε ′ ( z ) and ε ′′ ( z ) are the real and imaginary parts of the effective dielectric constant, respectively.…”

Section: Simulation Approachmentioning

confidence: 99%

“…Apollo in situ measurements showed that most of the lunar surface consists of a fine‐grained regolith layer that covers the underlying, highly fractured basement materials (i.e., megaregolith). The average thickness of the fine‐grained regolith layer is 4–5 m for the maria and 10–15 m for the highlands (Fa & Jin, ; Montopoli et al, ; Shkuratov & Bondarenko, ). The penetration depths of 19.35‐ and 37‐GHz microwaves are no more than 1 m on the Moon (Fang & Fa, ; Wang et al, ), which is smaller than the typical thickness of the regolith.…”

Section: Simulation Approachmentioning

confidence: 99%

A New Method for Simulation of Lunar Microwave Brightness Temperatures and Evaluation of Chang'E‐2 MRM Data Using Thermal Constraints From Diviner

Wei

Hong

et al. 2019

JGR Planets

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We used the bolometric brightness temperatures (TBol) derived from the Lunar Reconnaissance Orbiters Diviner Lunar Radiometer (Diviner) as an upper boundary condition in our thermal model. We then calculated temperature profiles at any local time based on our improved thermal model at low to middle latitudes (70° N/S). Based on the temperature profiles, we modeled the midnight brightness temperature at 19.35 (TB19) and 37 GHz (TB37). Comparing to the Chang'E‐1 and Chang'E‐2 (CE‐1/2) observations, we found that CE‐1 showed a better data quality than that of CE‐2, especially for the TB37 data. Assuming that the issue with the CE‐2 data is caused by heat contamination of the cold‐reference antennas, we performed an empirical normalization of the CE‐2 microwave radiometer data near midnight following the approach of Hu et al. (2017). The results show that TB difference (modeled values minus modified TB) for 19.35 GHz is less than 3.40 K for ∼80% of the pixels. At 37 GHz, ∼67% of the pixels have TB difference less than 2.88 K. Additionally, we identified some areas of low microwave temperature in our modified TB maps. These low‐TB features can be characterized by two types: (1) low TB spots at fresh craters with high rock abundance and bright rays and (2) high‐Ti lunar mare surfaces with a low content of rock fragments. Investigating these low‐TB regions with the modified TB data can reveal more information about subsurface thermal regime and properties and help us better understand the evolution of regolith on the Moon.

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“…Using a lunar sample from the Apollo mission [37] and employing a nonlinear regression, Montopoli et al [39], [40] proposed the following dielectric permittivity model:…”

Section: B Tb Computation 1) Dielectric Permittivity Of Lunar Regolithmentioning

confidence: 99%

Brightness Temperature Calculation of Lunar Crater: Interpretation of Topographic Effect on Microwave Data From Chang'E

Chen

Huang

et al. 2014

IEEE Trans. Geosci. Remote Sensing

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In order to quantitatively interpret topographic effect on Chang'E (CE) microwave data, a detailed method to compute brightness temperature (TB) over a lunar crater is proposed, which incorporated the effect of surface tilts. The method improves the effective solar irradiance model of the lunar surface to obtain the temperature profile of the lunar crater. The calculated TB at 37 GHz with the proposed computation method, which is based on three digital elevation models (DEMs) from different sources, are consistent with the observed TB from the CE-2 microwave radiometer. The simulated behavior of TB across crater Hercules reproduces the TB undulation observed by CE in a single swath. TB is significantly affected by the lunar dust of a lunar crater and affected by albedo and emissivity in a lesser degree. Based on the explanation with simplified models, the TB variation over a crater is proved to be significantly affected, through physical temperature, by the crater shape described by DEMs. With the simplified crater model, the amplitude of the TB oscillatory curves is proved to depend on the crater shape.Index Terms-Brightness temperature (TB), Chang'E (CE), digital elevation model (DEM), lunar crater.

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Remote sensing of the Moon's subsurface with multifrequency microwave radiometers: A numerical study

Cited by 30 publications

References 24 publications

New Constraints on Thermal and Dielectric Properties of Lunar Regolith from LRO Diviner and CE‐2 Microwave Radiometer

New Constraints on Thermal and Dielectric Properties of Lunar Regolith from LRO Diviner and CE‐2 Microwave Radiometer

A New Method for Simulation of Lunar Microwave Brightness Temperatures and Evaluation of Chang'E‐2 MRM Data Using Thermal Constraints From Diviner

Brightness Temperature Calculation of Lunar Crater: Interpretation of Topographic Effect on Microwave Data From Chang'E

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