Chandrayaan-2 dual-frequency SAR: Further investigation into lunar water and regolith

Putrevu, Deepak; Das, Anup; Vachhani, J. G.; Trivedi, Shivam; Misra, Tapan

doi:10.1016/j.asr.2015.10.029

Cited by 27 publications

(8 citation statements)

References 19 publications

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“…The Dual-Frequency Synthetic Aperture Radar (DFSAR) aboard India's second lunar mission Chandrayaan-2 is the first fully polarimetric synthetic aperture radar (SAR) outside Earth orbit. The architecture of this radar instrument supports multiple polarimetric modes of operation (Putrevu et al 2016(Putrevu et al , 2020, and illustrates the value of dual-frequency quad polarimetry for lunar and planetary applications. Regarding applications to the lunar surface, the main novelties provided by this instrument are the following:…”

Section: Introductionmentioning

confidence: 94%

“…The DFSAR instrument is designed with a configuration that enables operations in dual-frequency, quad-and compact-polarity imaging modes to collect information about the scattering properties of the lunar surface at multiple look-angle geometry. For a complete review of technical specifications, system design and configuration of the DFSAR instrument, the reader is referred to Putrevu et al (2016) and Putrevu et al (2020). In this section, we briefly describe the system configuration, followed by calibration of DFSAR data products.…”

Section: Dfsar Instrument Overview Operations and Calibrationmentioning

confidence: 99%

“…from normal incidence to ∼ 20 • ), the reflection is dominated by locally smooth, radar-facing facets of the surface, and for incidence angles beyond ∼ 30 • diffuse scattering from the small-scale roughness predominates (Hagfors 1964;Farr 1993). The DFSAR instrument is designed to collect data at a wide range of angles of incidence, from 9.6 • to 36.9 • (Putrevu et al 2016(Putrevu et al , 2020). This capability enables acquisition of dual-wavelength (L-and S-bands) radar images at multiple viewing angles to address some important applications such as the estimation of wavelength-scale physical properties (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Chandrayaan-2 Dual-Frequency SAR (DFSAR): Performance Characterization and Initial Results

Bhiravarasu,

Chakraborty,

Putrevu

et al. 2021

Preprint

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The Dual-Frequency synthetic aperture radar (DFSAR) system manifested on the Chandrayaan-2 spacecraft represents a significant step forward in radar exploration of solid solar system objects. It combines SAR at two wavelengths (L-and S-bands) and multiple resolutions with several polarimetric modes in one lightweight (∼ 20 kg) package. The resulting data from DFSAR support calculation of the 2×2 complex scattering matrix for each resolution cell, which enables lunar near surface characterization in terms of radar polarization properties at different wavelengths and incidence angles. In this paper, we report on the calibration and preliminary performance characterization of DFSAR data based on the analysis of a sample set of crater regions on the Moon. Our calibration analysis provided a means to compare on-orbit performance with pre-launch measurements and the results matched with the pre-launch expected values. Our initial results show that craters in both permanently shadowed regions (PSRs) and non-PSRs that are classified as Circular Polarization Ratio (CPR)-anomalous in previous S-band radar analyses appear anomalous at L-band also. We also observe that material evolution and physical properties at their interior and proximal ejecta are decoupled. For Byrgius C crater region, we compare our analysis of dual-frequency radar data with the predicted behaviours of theoretical scattering models. If crater age estimates are available, comparison of their radar polarization properties at multiple wavelengths similar to that of the three unnamed south polar crater regions shown in this study may provide new insights into how the rockiness of craters evolves with time.

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Section: Introductionmentioning

confidence: 94%

Section: Dfsar Instrument Overview Operations and Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chandrayaan-2 Dual-Frequency SAR (DFSAR): Performance Characterization and Initial Results

Bhiravarasu,

Chakraborty,

Putrevu

et al. 2021

Preprint

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“…The added information from full-polarimetric data will allow greater confidence in the results derived particularly in detecting the presence and estimating the quantity of water ice in the polar region. The DFSAR is designed, developed and provided by SAC, Ahmedabad (Putrevu et al, 2016).…”

Section: Dual Frequency Synthetic Aperture Radar (Dfsar)mentioning

confidence: 99%

Chandrayaan-2: India’s Second Lunar Exploration Mission

Kosambe

2019

Journal of Aircraft and Spacecraft Technology

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The Moon has always been the center of attention for mankind, more than any other heavenly body in the night sky. With the early history of the solar system etched on it, the Moon challenges mankind from time immemorial to discover its secrets and admire its marvels. Understanding the Moon will provide us a pathway to unravel the early evolution of the solar system and that of planet Earth. Almost twelve years after its first lunar exploration mission, India bounced back towards Moon with Chandrayaan-2. India's most advanced engineering marvel Chandrayaan-2 is on a mission unlike any before. Leveraging nearly a decade of scientific research and engineering development, India's second lunar expedition will shed light on a completely unexplored region of the Moon, its South Polar Region. The indigenously built Chandrayaan-2 consists of an orbiter, a lander (Vikram) along with a rover (Pragyan). With the payload of completely home-grown technologies, it will help us to gain a better understanding of the origin and evolution of the Moon by conducting detailed topographical studies, comprehensive mineralogical analysis and a host of other experiments. The Chandrayaan-2 is India's first robotic exploration mission to attempt a soft landing on the South Polar Region of the Moon. With the success of this mission, India became the fifth country ever to attempt a soft landing on the lunar surface. This paper provides an insight into the Chandrayaan-2 Mission. Additionally, an overview of the mission profile, challenges involved, launch vehicle architecture, spacecraft configuration and scientific payloads are also presented.

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“…Full‐polarimetry (with coherent measurements in HH, HV, VV, and VH polarization combinations) is considered to be gold standard in radar polarimetric studies and therefore, enables an extended measurement dimension to uniquely characterize the targets of interest. L‐ & S‐band Dual‐Frequency Synthetic Aperture Radar (DFSAR) onboard Chandrayaan‐2 (Ch2) orbiter (2019) is the first SAR with full‐polarimetric capability in a lunar orbit, and therefore, meets the above expectations of measurements (Putrevu et al., 2016, 2020b).…”

Section: Introductionmentioning

confidence: 99%

Lunar Impact Craters: New Perspectives From Full‐Polarimetric Analysis of Chandrayaan‐2 Dual‐Frequency SAR Data

Putrevu,

Chakraborty,

Mukhopadhyay

et al. 2023

JGR Planets

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With the availability of the full‐polarimetry data from Chandrayaan‐2 Dual‐frequency Synthetic Aperture Radar (DFSAR) for the first time, the lunar impact craters are studied for comprehensive characterization, which was earlier limited due to hybrid‐polarimetry based observations. In conjunction with the conventional Circular Polarization Ratio (CPR), we explore the unique full‐polarimetric parameters such as Single‐bounce Eigenvalue Relative Difference and T‐Ratio which are sensitive to surface roughness and dielectric constant, respectively. We studied the polarimetric behavior of a total of 115 nos. of impact craters within a specific size range (∼1–25 km diameter) belonging to different categories viz. fresh, degraded, polar and non‐polar anomalous craters. Our results confirm that both kinds of non‐polar and polar anomalous craters overall hold centimeter‐decimeter scale surface roughness similar to the exterior of the fresh craters, which mainly leads to the anomalous nature of the craters. Our analysis indicates possible control of the crater degradation process on the change in the radar scattering behavior of the studied lunar craters. The crater degradation causes a reduction in the surface roughness and dielectric property (density) of the scatterers present in various craters leading to a change in the radar scattering behavior. Alongside, water ice, if at all present admixed into the regolith in the polar anomalous craters, is not in the form of dominant scatterers that can influence the radar signature. However, the occurrence of relatively higher CPR values in smooth low dielectric crater interiors supports the possibility of the presence of water ice in some of the studied polar anomalous craters belonging to Pre‐Imbrian to Imbrian lunar geological periods.

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Chandrayaan-2 dual-frequency SAR: Further investigation into lunar water and regolith

Cited by 27 publications

References 19 publications

Chandrayaan-2 Dual-Frequency SAR (DFSAR): Performance Characterization and Initial Results

Chandrayaan-2 Dual-Frequency SAR (DFSAR): Performance Characterization and Initial Results

Chandrayaan-2: India’s Second Lunar Exploration Mission

Lunar Impact Craters: New Perspectives From Full‐Polarimetric Analysis of Chandrayaan‐2 Dual‐Frequency SAR Data

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