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Title of article :
Shape modeling technique KOALA validated by ESA Rosetta at (21) Lutetia
Author/Authors :
Carry، نويسنده , , B. and Kaasalainen، نويسنده , , M. and Merline، نويسنده , , W.J. and Müller، نويسنده , , T.G. and Jorda، نويسنده , , L. and Drummond، نويسنده , , J.D. and Berthier، نويسنده , , J. and OʹRourke، نويسنده , , L. and ?urech، نويسنده , , J. and Küppers، نويسنده , , M. and Conrad، نويسنده , , A. and Tamblyn، نويسنده , , P. and Dumas، نويسنده , , C. and Sierks، نويسنده , , H.، نويسنده ,
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روزنامه با شماره پیاپی سال 2012
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Abstract :
We present here a comparison of our results from ground-based observations of asteroid (21) Lutetia with imaging data acquired during the flyby of the asteroid by the ESA Rosetta mission. This flyby provided a unique opportunity to evaluate and calibrate our method of determination of size, 3-D shape, and spin of an asteroid from ground-based observations. Knowledge of certain observable physical properties of small bodies (e.g., size, spin, 3-D shape, and density) have far-reaching implications in furthering our understanding of these objects, such as composition, internal structure, and the effects of non-gravitational forces. We review the different observing techniques used to determine the above physical properties of asteroids and present our 3-D shape-modeling technique KOALA – Knitted Occultation, Adaptive-optics, and Lightcurve Analysis – which is based on multi-dataset inversion. We compare the results we obtained with KOALA, prior to the flyby, on asteroid (21) Lutetia with the high-spatial resolution images of the asteroid taken with the OSIRIS camera on-board the ESA Rosetta spacecraft, during its encounter with Lutetia on 2010 July 10. The spin axis determined with KOALA was found to be accurate to within 2°, while the KOALA diameter determinations were within 2% of the Rosetta-derived values. The 3-D shape of the KOALA model is also confirmed by the spectacular visual agreement between both 3-D shape models (KOALA pre- and OSIRIS post-flyby). We found a typical deviation of only 2 km at local scales between the profiles from KOALA predictions and OSIRIS images, resulting in a volume uncertainty provided by KOALA better than 10%. Radiometric techniques for the interpretation of thermal infrared data also benefit greatly from the KOALA shape model: the absolute size and geometric albedo can be derived with high accuracy, and thermal properties, for example the thermal inertia, can be determined unambiguously. The corresponding Lutetia analysis leads to a geometric albedo of 0.19±0.01 and a thermal inertia below 40 J m−2 s−0.5 K−1, both in excellent agreement with the Rosetta findings. We consider this to be a validation of the KOALA method. Because space exploration will remain limited to only a few objects, KOALA stands as a powerful technique to study a much larger set of small bodies using Earth-based observations.
Keywords :
asteroid , Rosetta , Koala , Disk-resolved imaging , (21) Lutetia
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