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Thermal Inertia Determination of C-type Asteroid Ryugu from in-situ Surface Brightness Temperature Measurements

Hamm, Maximilian and Grott, M. and Knollenberg, J. and Kührt, E. and Pelivan, Ivanka (2016) Thermal Inertia Determination of C-type Asteroid Ryugu from in-situ Surface Brightness Temperature Measurements. American Astronomical Society, DPS meeting #48, USA.

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Abstract

The Japanese Hayabusa-2 mission is a sample-return mission currently on its way to the C-type asteroid Ryugu. Hayabusa-2 carries the small lander MASCOT (Mobile Asteroid Surface Scout), whose scientific payload includes the infrared radiometer MARA. The primary science goal of MARA is to determine Ryugu's surface brightness temperatures at the landing site for a full asteroid rotation, which will be measured using a long-pass filter, an 8 to 12 µm bandpass, as well as four narrow bandpasses centered at wavelengths between 5 and 15 µm. From these measurements, surface thermal inertia will be derived, but because MARA performs single pixel measurements, heterogeneity in the field of view cannot be resolved. Yet, the surface will likely exhibit different surface textures, and thermal inertia in the field of view could vary from 600 (small rocks) to 50 Jm-2s-0.5K-1 (fine regolith grains). Sub-pixel heterogeneity is a common problem when interpreting radiometer data, since the associated ambiguities cannot be resolved without additional information on surface texture. For MARA, this information will be provided by the MASCOT camera, and in the present paper we have investigated to what extent different thermal inertias can be retrieved from MARA data. To test the applied approach, we generated synthetic MARA data using a thermal model of Ryugu, assuming different thermal inertias for sections of the field of view. We find that sub-pixel heterogeneity systematically deforms the diurnal temperature curve so that it is not possible to fit the data using a single thermal inertia value. However, including the area fractions of the different surface sections enables us to reconstruct the different thermal inertias to within 10% assuming appropriate measurement noise. The presented approach will increase robustness of the Ryugu thermal inertia determination and results will serve as a ground truth for the global measurements performed by the thermal infrared mapper (TIR) on the Hayabusa-2 main spacecraft.

Item URL in elib:https://elib.dlr.de/108574/
Document Type:Conference or Workshop Item (Speech)
Title:Thermal Inertia Determination of C-type Asteroid Ryugu from in-situ Surface Brightness Temperature Measurements
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Hamm, Maximilianmaximilian.hamm (at) dlr.deUNSPECIFIED
Grott, M.matthias.grott (at) dlr.deUNSPECIFIED
Knollenberg, J.joerg.knollenberg (at) dlr.deUNSPECIFIED
Kührt, E.ekkehard.kuehrt (at) dlr.deUNSPECIFIED
Pelivan, Ivankaivanka.pelivan (at) dlr.deUNSPECIFIED
Date:2016
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Hayabusa; MASCOT; MARA;
Event Title:American Astronomical Society, DPS meeting #48
Event Location:USA
Event Type:international Conference
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 > Asteroids and Comets
Deposited By: Schubert, Renate
Deposited On:30 Nov 2016 08:05
Last Modified:30 Nov 2016 08:05

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