The Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) is a multi-frequency, multi-channel ice penetrating radar system that will be flown on board the Europa Clipper mission to Jupiter's moon Europa. REASON investigation will provide the first direct measurements of Europa's ice shell surface character and subsurface structure.REASON for Europa. Moussessian, A.; Blankenship, D. D.; Plaut, J. J.; Patterson, G. W.; Gim, Y.; Schroeder, D. M.; Soderlund, K. M.; Grima, C.; Young, D. A.; Chapin, E. American Geophysical Union, Fall Meeting 2015, abstract #P13E-05. December 2015.
Overview
The REASON instrument makes innovative use of radar sounding, altimetry, reflectometry, plasma and particles analyses. These investigations will use a dual-frequency radar emitting HF (9 MHz) and VHF (60 MHz) with concurrent shallow and deep sounding. Both VHF and HF radiating elements are mounted on a single boom, reducing antenna mass. The mission plan also includes using REASON as a nadir altimeter capable of measuring tides to test ice shell and ocean hypotheses as well as characterizing roughness across the surface to identify potential landing sites for a future Europa Lander.
The REASON instrument will also be able to spot pockets of water within the ice shell that could serve as a passageway for chemicals on the moon's surface to the ocean below — an environment where life could potentially develop.
The instrument was developed by the Jackson School of Geosciences, and its Principal Investigator is Donald Blankenship. REASON was fabricated by engineers from NASA's Jet Propulsion Laboratory and the University of Iowa.
Specifications table REASON Units/performance Electronics mass 17.5 kg Antenna mass 14.7 kg Total mass 32.2 kg Operating power 55 W Antenna length VHF(shallow sounding) 300 m to 4.5 km HF(deep sounding) 1 km to 30 km Pulse length 30 - 100 μs Operational altitude 10 - 1000 km Radar potential HF: 63 dBVHF: 72 dB Data rate 5 - 80 Mbps Data volumeper flyby 24 Gbits
Objectives
The scientific objectives of the REASON investigation are: Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) (PDF). D. Blankenship. 2015 Characterize the distribution of any shallow subsurface water Search for an ice-ocean interface and characterize the ice shell's global structure Investigate the processes governing material exchange among the ocean, ice shell, surface, and atmosphere Constrain the amplitude and phase of gravitational tides Characterize scientifically compelling sites, and hazards, for a potential future Europa Lander mission
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