Radar for Europa Assessment and Sounding: Ocean to Near-Surface (REASON)
Authors: Blankenship Donald D. , Moussessian Alina , Chapin Elaine , Young Duncan A. , Wesley Patterson G. , Plaut Jeffrey J. , Freedman Adam P. , Schroeder Dustin M. , Grima Cyril , Steinbrügge Gregor , Soderlund Krista M. , Ray Trina , Richter Thomas G. , Jones-Wilson Laura , Wolfenbarger Natalie S. , Scanlan Kirk M. , Gerekos Christopher , Chan Kristian , Seker Ilgin , Haynes Mark S. , Barr Mlinar Amy C. , Bruzzone Lorenzo , Campbell Bruce A. , Carter Lynn M. , Elachi Charles , Gim Yonggyu , Hérique Alain , Hussmann Hauke , Kofman Wlodek , Kurth William S. , Mastrogiuseppe Marco , McKinnon William B. , Moore Jeffrey M. , Nimmo Francis , Paty Carol , Plettemeier Dirk , Schmidt Britney E. , Zolotov Mikhail Y. , Schenk Paul M. , Collins Simon , Figueroa Harry , Fischman Mark , Tardiff Eric , Berkun Andy , Paller Mimi , Hoffman James P. , Kurum Andy , Sadowy Gregory A. , Wheeler Kevin B. , Decrossas Emmanuel , Hussein Yasser , Jin Curtis , Boldissar Frank , Chamberlain Neil , Hernandez Brenda , Maghsoudi Elham , Mihaly Jonathan , Worel Shana , Singh Vik , Pak Kyung , Tanabe Jordan , Johnson Robert , Ashtijou Mohammad , Alemu Tafesse , Burke Michael , Custodero Brian , Tope Michael C. , Hawkins David , Aaron Kim , Delory Gregory T. , Turin Paul S. , Kirchner Donald L. , Srinivasan Karthik , Xie Julie , Ortloff Brad , Tan Ian , Noh Tim , Clark Duane , Duong Vu , Joshi Shivani , Lee Jeng , Merida Elvis , Akbar Ruzbeh , Duan Xueyang , Fenni Ines , Sanchez-Barbetty Mauricio , Parashare Chaitali , Howard Duane C. , Newman Julie , Cruz Marvin G. , Barabas Neil J. , Amirahmadi Ahmadreza , Palmer Brendon , Gawande Rohit S. , Milroy Grace , Roberti Rick , Leader Frank E. , West Richard D. , Martin Jan , Venkatesh Vijay , Adumitroaie Virgil , Rains Christine , Quach Cuong , Turner Jordi E. , O’Shea Colleen M. , Kempf Scott D. , Ng Gregory , Buhl Dillon P. , Urban Timothy J. 
Published: June 2024

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.