ICEE: Instrument Concepts for Europa Exploration
By Cynthia Phillips
In 2013, NASA offered a new research program solicitation called Instrument Concepts for Europa Exploration (ICEE), as part of the Outer Planets program of NASA's Planetary Science Division. ICEE offered an opportunity to the scientific and engineering community to submit proposals for development and maturation of instrument concepts for a potential strategic mission to Europa, thereby reducing technical risks of that mission. The goal of the program was to produce mature instrument concepts that could be proposed to a future mission announcement of opportunity (AO) without requiring future long periods of technological development before flight hardware selection and construction could ultimately begin.
During the short time applications were open, 28 compliant proposals were submitted and reviewed, and 15 of these proposals were recently selected for funding. Details of the selections have been provided by the ICEE Program Scientist at NASA, Dr. Curt Niebur, including a briefing to the ICEE teams, available here and to the Outer Planets Assessment Group. The distribution of instruments selected for study included a wide variety of instrument types.
| Instrument Type || Number of Proposals || Number of Selections |
| Infrared Spectrometer || 4 || 3 |
| Mass Spectrometer || 5 || 3 |
| Topographical Imager || 3 || 2 |
| Ice-Penetrating Radar || 1 || 1 |
| Thermal Instrument || 3 || 2 |
| Gravity Science || 1 || 0 |
| Magnetometry || 4 || 2 |
| Plasma || 4 || 1 |
| Other || 3 || 1 |
| Total || 28 || 15 |
Information reported by Curt Niebur, NASA Program Manager for ICEE
The instruments selected for technology development included two topographical imagers; two thermal imagers; one laser altimeter; three magnetic-field-related instruments including a Faraday cup, a Langmuir probe, and a magnetometer; an ice-penetrating radar; three short-wavelength infrared spectrometers; three mass spectrometers; and a dust analyzer.
Each instrument type could support the objectives, investigations and measurements of the Europa Clipper mission concept; instruments similar to a type in the model payload that were identified as being in particular need of maturation and technology development were given a slight review advantage. Those instrument types included ice-penetrating radar, shortwave infrared spectrometer, topographical imager and mass spectrometer.
Specifically, the ICEE proposals selected for study funding were:
Topographical imagers: The topographical imager instrument concept is a capable camera that could map large tracts of Europa's surface at resolutions down to 80 to 660 feet (25 to 200 meters) per pixel. It would use stereo imaging capability to produce 3-D topographic views of the surface. Two topographical imagers were selected for further development by ICEE. One is led by Elizabeth "Zibi" Turtle from the Johns Hopkins University Applied Physics Lab (APL), and the second is led by Jim Bell from Arizona State University.
Thermal Imagers: A thermal imager would help with reconnaissance and landing site characterization to aid in the selection of safe and scientifically compelling landing sites for a possible future landed mission. Thermal measurements would help to constrain the properties of the surface, including the existence and distribution of ice boulders. Such an instrument could potentially also be used to identify anomalously warm regions of the surface and could be key in the search for locations where the surface is geologically active, such as the source regions of suspected plumes. Two thermal instruments were selected for further development by ICEE: a thermal imager instrument led by Shahid Aslam of NASA Goddard Spaceflight Center (GSFC), and a thermal radiometer led by Matt Kenyon of NASA's Jet Propulsion Laboratory (JPL).
Laser Altimeters: A laser altimeter could directly measure the height of Europa's tide by measuring surface deflections at different positions in Europa's orbit around Jupiter. It could also potentially be used to take detailed topographic profiles over regions of interest under the ground track of a spacecraft at closest approach during a flyby. One laser altimeter was selected for further development under ICEE, led by David Smith of the Massachusetts Institute of Technology.
Magnetometers and Plasma Instruments: During NASA's Galileo mission to Jupiter in the mid-1990s and early 2000s, magnetometer measurements detected an induced magnetic field at Europa, providing the best evidence to date for a global subsurface conducting layer, thought to be a subsurface ocean of salty water. Among the selected ICEE proposals is a magnetometer, led by Carol Raymond of JPL. Accurately assessing Europa's induced field response requires having a firm understanding of the charged particle environment or its electric field signature. To address this issue, two instrument concepts were selected for further development. A Faraday Cup instrument suite, led by Joe Westlake from APL, would measure the plasma contributions near Europa. Moreover, a Langmuir Probe instrument would determine plasma effects, as led by Fran Bagenal from University of Colorado.
Radar: A radar sounder could characterize water within and potentially beneath the ice shell by searching for reflections from subsurface water bodies. A radar instrument would penetrate through the ice, and, depending on the ice's thermal, chemical and physical properties, could sense any inclusions of liquid water and perhaps the ice-water interface as well. One radar instrument was selected for maturation under ICEE, led by Alina Moussessian of JPL.
Short-wave Infrared Spectrometers: This instrument type would study the surface composition of Europa. An imaging spectrometer could potentially provide compositional information at high spatial and spectral resolution, allowing identifications of the non-ice components on Europa's surface. Three short-wave infrared spectrometers were selected for further development under ICEE: one led by Rob Green of JPL, one led by Dennis Reuter of GSFC, and one led by Kevin Hand of JPL.
Mass Spectrometers: The final instrument type selected by ICEE included various kinds of mass spectrometers. Such instruments could measure the composition of specific particles by using unique molecular weights for identification. A mass spectrometer could measure the composition of particles sputtered off the surface of Europa or ejected through plume activity, without requiring a spacecraft to land on Europa's surface. Three mass spectrometers were selected for further development under ICEE. These included a mass spectrometer developed by Hunter Waite of Southwest Research Institute; a dust analyzer proposed by Sascha Kempf of University of Colorado, and a neutral mass spectrometer proposed by Murray Darrach of JPL.
The 15 instruments selected each have one year of support for development. During the study term, each team is encouraged to converse with scientists and engineers at NASA who are part of the Europa Clipper Formulation Team, and other potential instrument providers are encouraged to talk with the Formulation Team as well. The Clipper Formulation Team is ensuring that information shared with ICEE teams is also available to the general scientific community via the Europa Technical Resources pages.
Dr. Cynthia Phillips is a planetary geologist based at the SETI Institute, in Mountain View, CA, who has devoted much of her career to studying the icy moons of the outer solar system. Her favorite place is Europa.