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Proceedings Paper

SPEX: an in-orbit spectropolarimeter for planetary exploration
Author(s): Frans Snik; Theodora Karalidi; Christoph Keller; Erik Laan; Rik ter Horst; Ramon Navarro; Daphne Stam; Christina Aas; Johan de Vries; Gijs Oomen; Ruud Hoogeveen
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Paper Abstract

SPEX (Spectropolarimeter for Planetary EXploration) is an innovative, compact remote-sensing instrument for detecting and characterizing aerosols. With its 1-liter volume it is capable of full linear spectropolarimetry, without moving parts. High precision polarimetry is performed through encoding the degree and angle of linear polarization of the incoming light in a sinusoidal modulation of the intensity spectrum. This is achieved by using an achromatic quarter-wave retarder, an athermal multiple-order retarder and a polarizing beamsplitter behind each entrance pupil. Measuring a single intensity spectrum thus provides the spectral dependence of the degree and angle of linear polarization. Polarimetry has proven to be an excellent tool to study microphysical properties (size, shape, composition) of atmospheric particles. Such information is essential to better understand the weather and climate of a planet. Although SPEX can be used to study any planetary atmosphere, including the Earth's, the current design of SPEX is tailored to study Martian dust and ice clouds from an orbiting platform: a compact module with 9 entrance pupils to simultaneously measure intensity spectra from 350 to 800 nm, in different directions along the flight direction (including two limb viewing directions). This way, both the intensity and polarization scattering phase functions of dust and cloud particles within a ground pixel are sampled while flying over it. In the absence of significant amounts of dust and clouds, the surface properties can be studied. SPEX provides synergy with instruments on rovers and landers, as it provides a global view of spatial and temporal variations of the planet.

Paper Details

Date Published: 12 July 2008
PDF: 10 pages
Proc. SPIE 7010, Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, 701015 (12 July 2008); doi: 10.1117/12.787218
Show Author Affiliations
Frans Snik, Sterrekundig Instituut Utrecht (Netherlands)
Theodora Karalidi, Sterrekundig Instituut Utrecht (Netherlands)
Christoph Keller, Sterrekundig Instituut Utrecht (Netherlands)
Erik Laan, TNO Science and Industry (Netherlands)
Rik ter Horst, NOVA-ASTRON (Netherlands)
Ramon Navarro, NOVA-ASTRON (Netherlands)
Daphne Stam, Technische Univ. Delft (Netherlands)
SRON Netherlands Institute for Space Research (Netherlands)
Christina Aas, Technische Univ. Delft (Netherlands)
Johan de Vries, Dutch Space (Netherlands)
Gijs Oomen, Dutch Space (Netherlands)
Ruud Hoogeveen, SRON Netherlands Institute for Space Research (Netherlands)

Published in SPIE Proceedings Vol. 7010:
Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter
Jacobus M. Oschmann Jr.; Mattheus W. M. de Graauw; Howard A. MacEwen, Editor(s)

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