TransSounder: A Hybrid TransUNet-TransFuse Architectural Framework for Semantic Segmentation of Radar Sounder Data

The radar sounder data (radargrams) are used in this research work for subsurface target characterizations.<div>We develop a hybrid Transformer-based Deep Learning framework in the domain of semantic segmentation of radar sounder data.</div>

EnVision: Understanding why Earth's closest neighbour is so different

&lt;p&gt;EnVision is a proposed orbiter mission aiming at determining the nature and current state of Venus' geological evolution and its relationship with the atmosphere, to understand how and why Venus and Earth evolved so differently. It is is one of two M5 mission concepts in Phase A study with a final down-selection expected in June 2021. EnVision&amp;#8217;s overall science goals are&lt;br /&gt;&lt;br /&gt;- to&amp;#160;&lt;strong&gt;characterise&lt;/strong&gt;&amp;#160;the sequence of events that generated the regional and global surface features of Venus, and characterize the geodynamics framework that controls the release of internal heat over Venus history;&amp;#160;&lt;br /&gt;&lt;br /&gt;-&amp;#160;to&lt;strong&gt;&amp;#160;search&lt;/strong&gt;&amp;#160;for ongoing geological processes and determine&lt;strong&gt;&amp;#160;&lt;/strong&gt;whether the planet is active in the present era;&lt;br /&gt;&lt;br /&gt;-&amp;#160;to&amp;#160;&lt;strong&gt;characterise&lt;/strong&gt;&amp;#160;regional and local geological units, to better assess whether Venus once had condensed liquid water on its surface and was thus perhaps hospitable for life in its early history.&lt;br /&gt;&lt;br /&gt;EnVision will deliver new insights into geological history through complementary imagery, polarimetry, radiometry and spectroscopy of the surface coupled with subsurface sounding and gravity mapping; it will search for thermal, morphological, and gaseous signs of volcanic and other geological activity; and it will trace the fate of key volatile species from their sources and sinks at the surface through the clouds up to the mesosphere.&lt;br /&gt;&lt;br /&gt;EnVision&amp;#8217;s science payload consists of VenSAR, a dual polarization S-band radar also operating as microwave radiometer, three spectrometers VenSpec-M, VenSpec-U and VenSpec-H designed to observe the surface and atmosphere of Venus, and the Subsurface Radar Sounder (SRS), a High Frequency (HF) sounding radar to probe the subsurface. These are complemented by a radio science investigation which achieves gravity mapping and radio occultation of the atmosphere, for a comprehensive investigation of the Venusian surface, interior and atmosphere and their interactions.&lt;/p&gt;

Brief communication: An empirical relation between center frequency and measured thickness for radar sounding of temperate glaciers

Radar sounding of the thickness of temperate glaciers is challenged by substantial volume scattering, surface scattering and high attenuation rates. Lower-frequency radar sounders are often deployed to mitigate these effects, but the lack of a global synthesis of their success limits progress in system and survey design. Here we extend a recent global compilation of glacier thickness measurements (GlaThiDa) with the center frequency for radar-sounding surveys. From a maximum reported thickness of ∼ 1500 m near 1 MHz, the maximum thickness sounded decreases by ∼ 500 m per frequency decade. Between 25–100 MHz, newer airborne radar sounders generally outperform older, ground-based ones. Based on globally modeled glacier thicknesses, we conclude that a multi-element, ≤30 MHz airborne radar sounder could survey most temperate glaciers more efficiently.

Correction to: Estimation of bulk permittivity of the Moon’s surface using Lunar Radar Sounder on-board Selenological and Engineering Explorer

An amendment to this paper has been published and can be accessed via the original article.

Brief communication: An empirical relation between center frequency and measured thickness for radar sounding of temperate glaciers

Radar sounding of the thickness of temperate glaciers is more challenging than for polar ice sheets, due to the former's greater volume scattering (englacial water), surface scattering (crevasses and debris) and dielectric attenuation rate (warmer ice). Lower frequency (~1–100 MHz) radar sounders are commonly deployed to mitigate these effects, but the lack of a synthesis of existing radar-sounding surveys of temperate glaciers limits progress in system and survey design. Here we use a recent global synthesis of measured glacier thickness to evaluate the relation between the radar center frequency and maximum thickness. From a maximum reported thickness of ~1500 m near 1 MHz, the maximum thickness sounded decreases with increasing frequency by ~500 m per frequency decade. Newer airborne radar sounders generally outperform older, ground-based ones at comparable frequencies, so radar-sounder success is also influenced by system design and processing methods. Based on globally modeled glacier thicknesses, we conclude that a multi-element airborne radar sounder with a center frequency of ≤ 30 MHz could survey most temperate glaciers more efficiently than presently available systems.