Delay Doppler SAR Focusing and Quantitative Quality Control of the Radar for Europa Assessment and Sounding: Ocean to Near-Surface (REASON) Sounding Data Product

Scanlan, K. M.; Young, D. A.; Steinbrügge, Gregor; Kempf, S. D.; Grima, C.; Blankenship, D. D.

doi:10.1109/jstars.2021.3072276

Cited by 6 publications

(4 citation statements)

References 33 publications

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“…A detailed description of how REASON’s Doppler sampling requirements and the Europa Clipper mission design give rise to these unique idiosyncrasies is provided in Scanlan et al. ( 2021 ).…”

Section: Data Processing and Archivingmentioning

confidence: 99%

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Radar for Europa Assessment and Sounding: Ocean to Near-Surface (REASON)

Blankenship,

Moussessian,

Chapin

et al. 2024

Space Sci Rev

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The Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) is a dual-frequency ice-penetrating radar (9 and 60 MHz) onboard the Europa Clipper mission. REASON is designed to probe Europa from exosphere to subsurface ocean, contributing the third dimension to observations of this enigmatic world. The hypotheses REASON will test are that (1) the ice shell of Europa hosts liquid water, (2) the ice shell overlies an ocean and is subject to tidal flexing, and (3) the exosphere, near-surface, ice shell, and ocean participate in material exchange essential to the habitability of this moon. REASON will investigate processes governing this material exchange by characterizing the distribution of putative non-ice material (e.g., brines, salts) in the subsurface, searching for an ice–ocean interface, characterizing the ice shell’s global structure, and constraining the amplitude of Europa’s radial tidal deformations. REASON will accomplish these science objectives using a combination of radar measurement techniques including altimetry, reflectometry, sounding, interferometry, plasma characterization, and ranging. Building on a rich heritage from Earth, the moon, and Mars, REASON will be the first ice-penetrating radar to explore the outer solar system. Because these radars are untested for the icy worlds in the outer solar system, a novel approach to measurement quality assessment was developed to represent uncertainties in key properties of Europa that affect REASON performance and ensure robustness across a range of plausible parameters suggested for the icy moon. REASON will shed light on a never-before-seen dimension of Europa and – in concert with other instruments on Europa Clipper – help to investigate whether Europa is a habitable world.

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Section: Data Processing and Archivingmentioning

confidence: 99%

“…Due to the design of the Europa Clipper mission as a multiple flyby mission, the SAR focusing architecture must be tailored to REASON and will be distinct from previous orbital radar missions (Scanlan et al. 2021 ).…”

Section: Introductionmentioning

confidence: 99%

Radar for Europa Assessment and Sounding: Ocean to Near-Surface (REASON)

Blankenship,

Moussessian,

Chapin

et al. 2024

Space Sci Rev

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“…The usage of the raw products ensures that the data are free from ground-based post processing that could alter the radiometric gain through a terrain-dependent component hard to predict a priori. For instance, focusing techniques, commonly integrated in derived radar data products, have a radiometric stability dependent on the along-track surface backscattering function produced by roughness and local slopes (Peters et al 2007;Scanlan et al 2021). A SHARAD radargram can be of any length along the track, but has a fixed vertical size corresponding to a receiver window of 135 μs digitized over 3600 samples.…”

Section: The Shallow Radarmentioning

confidence: 99%

Investigating the Martian Surface at Decametric Scale: Population, Distribution, and Dimension of Heterogeneity from Radar Statistics

Grima¹,

Putzig²,

Perry³

et al. 2022

Planet. Sci. J.

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Building on one decade of theory and methodology maturation, we investigate the coherent and incoherent components of the response of the Martian surface to nadir-looking orbital radar. We apply a reflectometry technique known as radar statistical reconnaissance to Mars Reconnaissance Orbiter Shallow Radar data over a test region with a large dynamic range in echo strength. This technique provides a set of statistical parameters describing the heterogeneity of the surface and near-surface structure, presumably at a scale of ∼15 m. We discuss the physical meanings of these parameters related to surface and near-surface properties. Most (but not all) investigated terrains have a dominantly coherent surface return, a characteristic that is not necessarily indicative of a smooth surface. The observed behavior of the coherent and incoherent power components of the echo matches signal growth with increasing surface roughness. This finding allows us to identify smooth and level terrains that we use as a reference to approximate the surface height and slope variations of other regions. Nearly systematic mismatches between the SHARAD and MOLA-pulse-width roughness illustrate the complementarity of these data sets from their respective sensitivity range, and advocate for the use of self-affine radar backscattering models to account for roughness variations at different scales. Our methodology provides a wealth of surface properties assessment based on radar scattering with quasi-global coverage, without a dependence on other data, and at a decametric horizontal scale relevant to subregional geology investigation and landing site reconnaissance.

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“…On Earth, airborne ice‐penetrating radar sounders have been long and successfully used to constrain the structure and subsurface conditions of terrestrial ice sheets (e.g., Dowdeswell & Evans, 2004; Schroeder et al., 2020). Recently, orbital radar instruments MARSIS (Picardi et al., 2005) and SHARAD (Seu et al., 2007) have successfully investigated Mars' polar caps (Phillips et al., 2008; Plaut et al., 2007) and ice‐penetrating radar sounders will also be carried by the upcoming large missions to the icy moons—the RIME instrument (Bruzzone et al., 2015) onboard ESA's JUICE spacecraft and the REASON instrument (Blankenship et al., 2009; Scanlan et al., 2021) onboard NASA's Europa Clipper . The main goals of these instruments will be to search for the ocean interface and to study the distribution of shallow subsurface water as well as the thermophysical structure of the ice shell.…”

Section: Introductionmentioning

confidence: 99%

Radar Attenuation in Enceladus' Ice Shell: Obstacles and Opportunities for Constraining Shell Thickness, Chemistry, and Thermal Structure

et al. 2023

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Enceladus, a tiny moon of Saturn, is the subject of significant recent geophysical and astrobiological interest due mainly to the distinctive plumes emanating from its south-polar region (SPR). These plumes allowed the Cassini mission to sample the moon's interior and analyze the chemical composition. This analysis provided compelling evidence for direct contact between the silicate core and the internal ocean, and also for ongoing hydrothermal activity (Hsu et al., 2015;Schoenfeld et al., 2023;Waite et al., 2017). Consequently, Enceladus has been identified as a high-priority target for a search-for-life mission (Hendrix et al., 2019) and as the second highest priority new flagship-class mission for the upcoming decade (NASEM, 2022). Establishing constraints on the properties and structure of the ice shell and ocean is especially important in the context of life detection experiments and, more broadly, in the context of the moon's geophysical and geochemical evolution (Marusiak et al., 2021).Current knowledge of Enceladus' structure relies on gravity (Iess et al., 2014) and topography (Tajeddine et al., 2017;Thomas et al., 2007) inversions, which are sensitive to the underlying model assumptions. For example, the assumption of hydrostatic equilibrium combined with Airy isostasy initially led to an overestimation of the ice shell thickness (Iess et al., 2014;McKinnon, 2015). Moreover, it was not possible to prove the existence of Abstract Enceladus is a dynamic icy moon of Saturn and a leading target for future planetary missions focused on the search for life beyond Earth. For such missions, instruments that can provide geophysical and geochemical context for ice shell and ocean processes are critical to evaluate whether conditions are suitable for life and biosignature detection. Radar sounding is a powerful geophysical technique to probe the thermophysical and chemical properties of icy moons, like Enceladus, and to investigate the subsurface context for the exchange of material and energy between their subsurface oceans, ice shells, and plumes. To inform the scientific potential and instrument performance demands of such a radar-sounding investigation of Enceladus' ice shell, we adapt and extend previous radar attenuation analysis done for Europa to the configuration and conditions of Enceladus. We also discuss how attenuation (both as an obstacle for the detection of ice shell reflectors and as a signal itself) can help constrain the thermal, physical, and chemical configuration of Enceladus' ice shell and reveal the processes governing the moon's ocean/shell/plume system.Plain Language Summary Enceladus, a tiny icy moon of Saturn, has been attracting attention since the discovery of its spectacular water jet activity. The jets, sampling the moon's hidden deep ocean, have revealed conditions favorable for the existence of life below the cold outer ice shell. Understanding the long-term persistence of the ocean, the jets, and their connection to the ice shell and ocean requires reliable knowledge of the shell...

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Delay Doppler SAR Focusing and Quantitative Quality Control of the Radar for Europa Assessment and Sounding: Ocean to Near-Surface (REASON) Sounding Data Product

Cited by 6 publications

References 33 publications

Radar for Europa Assessment and Sounding: Ocean to Near-Surface (REASON)

Radar for Europa Assessment and Sounding: Ocean to Near-Surface (REASON)

Investigating the Martian Surface at Decametric Scale: Population, Distribution, and Dimension of Heterogeneity from Radar Statistics

Radar Attenuation in Enceladus' Ice Shell: Obstacles and Opportunities for Constraining Shell Thickness, Chemistry, and Thermal Structure

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