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On the effect of emergence angle on emissivity spectra: application to small bodies

Maturilli, Alessandro and Helbert, Jörn and Ferrari, Sabrina and D’Amore, M. (2016) On the effect of emergence angle on emissivity spectra: application to small bodies. Earth, Planets and Space, 68 (1). Springer. ISSN 1343-8832

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Official URL: http://dx.doi.org/10.1186/s40623-016-0464-7

Abstract

Dependence of laboratory-measured emissivity spectra from the emergence angle is a subject that still needs a lot of investigations to be fully understood. Most of the previous work is based on reflectance measurements in the VIS–NIR spectral region and on emissivity measurements of flat, solid surfaces (mainly metals), which are not directly applicable to the analysis of remote sensing data. Small bodies in particular (c.f. asteroids Itokawa and 1999JU3, the respective targets of JAXA Hayabusa and Hayabusa 2 missions) have a very irregular surface; hence, the spectra from those rough surfaces are difficult to compare with laboratory spectra, where the observing geometry is always close to “nadir.” At the Planetary Emissivity Laboratory of the German Aerospace Center (DLR), we have set up a series of spectral measurements to investigate this problem in the 1- to 16-µm spectral region. We measured the emissivity for two asteroid analogue materials (meteorite Millbillillie and a synthetic enstatite) in vacuum and under purged air, at surface temperature of 100 °C, for emergence angles of 0°, 5°, 10°, 20°, 30°, 40°, 50°, and 60°. Emissivity of a serpentinite slab, already used as calibration target for the MARA instrument on Hayabusa 2 MASCOT lander and for the thermal infrared imager spectrometer on Hayabusa 2 orbiter, was measured under the same conditions. Additionally, a second basalt slab was measured. Both slabs were not measured at 5° inclination. Complementary reflectance measurements of the four samples were taken. For all the samples measured, we found that for calibrated emissivity, significant variations from values obtained at nadir (0° emergence angle) appear only for emergence angles ≥40°. Reflectance measurements confirmed this finding, showing the same trend of variations.

Item URL in elib:https://elib.dlr.de/109393/
Document Type:Article
Title:On the effect of emergence angle on emissivity spectra: application to small bodies
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Maturilli, AlessandroAlessandro.Maturilli (at) dlr.deUNSPECIFIED
Helbert, JörnJoern.Helbert (at) dlr.deUNSPECIFIED
Ferrari, Sabrinasabrina.ferrari (at) dlr.deUNSPECIFIED
D’Amore, M.mario.damore (at) dlr.deUNSPECIFIED
Date:23 May 2016
Journal or Publication Title:Earth, Planets and Space
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:No
Volume:68
Publisher:Springer
ISSN:1343-8832
Status:Published
Keywords:The Hayabusa 2 mission Asteroid analogue materials Emissivity measurements Emergence angle Infrared spectroscopy
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Project MASCOT (old)
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Experimentelle Planetenphysik
Deposited By: Maturilli, Alessandro
Deposited On:15 Dec 2016 08:53
Last Modified:19 Apr 2018 05:03

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