TY - JOUR
T1 - Photometric, spectral phase and temperature effects on 4 Vesta and HED meteorites
T2 - Implications for the Dawn mission
AU - Reddy, Vishnu
AU - Sanchez, Juan A.
AU - Nathues, Andreas
AU - Moskovitz, Nicholas A.
AU - Li, Jian Yang
AU - Cloutis, Edward A.
AU - Archer, Ken
AU - Tucker, Roy A.
AU - Gaffey, Michael J.
AU - Paul Mann, J.
AU - Sierks, Holger
AU - Schade, Ulrich
N1 - Funding Information:
V.R. and M.J.G. were supported by NASA Dawn Participating Scientist Program Grant NNH09ZDA001N-DAVPS , NASA NEOO Program Grant NNX07AL29G , and NASA Planetary Geology and Geophysics Grant NNX07AP73G . The authors would like to thank, Reid Archer, Paul Lucey, and Brian Warner for their support in this research and Mike Hicks and Cristina Thomas for their helpful reviews. We thank the IRTF TAC for awarding time to this project, and to the IRTF TOs and MKSS staff for their support. J.A. Sanchez acknowledges a PhD fellowship of the International Max Planck Research School on Physical Processes in the Solar System and Beyond. E.A.C. thanks the Canada Foundation for Innovation, the Manitoba Research Innovation Fund, the Canadian Space Agency, and NSERC for funding to establish and operate HOSERLab.
PY - 2012/1
Y1 - 2012/1
N2 - Phase angle and temperature are two important parameters that affect the photometric and spectral behavior of planetary surfaces in telescopic and spacecraft data. We have derived photometric and spectral phase functions for the Asteroid 4 Vesta, the first target of the Dawn mission, using ground-based telescopes operating at visible and near-infrared wavelengths (0.4-2.5μm). Photometric lightcurve observations of Vesta were conducted on 15 nights at a phase angle range of 3.8-25.7° using duplicates of the seven narrowband Dawn Framing Camera filters (0.4-1.0μm). Rotationally resolved visible (0.4-0.7μm) and near-IR spectral observations (0.7-2.5μm) were obtained on four nights over a similar phase angle range. Our Vesta photometric observations suggest the phase slope is between 0.019 and 0.029. mag/deg. The G parameter ranges from 0.22 to 0.37 consistent with previous results (e.g., Lagerkvist, C.-I., Magnusson, P., Williams, I.P., Buontempo, M.E., Argyle, R.W., Morrison, L.V. [1992]. Astron. Astrophys. Suppl. Ser. 94, 43-71; Piironen, J., Magnusson, P., Lagerkvist, C.-I., Williams, I.P., Buontempo, M.E., Morrison, L.V. [1997]. Astron. Astrophys. Suppl. Ser. 121, 489-497; Hasegawa, S. et al. [2009]. Lunar Planet. Sci. 40. ID 1503) within the uncertainty. We found that in the phase angle range of 0°<.α≤. 25° for every 10° increase in phase angle Vesta's visible slope (0.5-0.7μm) increases 20%, Band I and Band II depths increase 2.35% and 1.5% respectively, and the BAR value increase 0.30. Phase angle spectral measurements of the eucrite Moama in the lab show a decrease in Band I and Band II depths and BAR from the lowest phase angle 13° to 30°, followed by possible small increases up to 90°, and then a dramatic drop between 90° and 120° phase angle. Temperature-induced spectral effects shift the Band I and II centers of the pyroxene bands to longer wavelengths with increasing temperature. We have derived new correction equations using a temperature series (80-400. K) of HED meteorite spectra that will enable interpretation of telescopic and spacecraft spectral data using laboratory calibrations at room temperature (300. K).
AB - Phase angle and temperature are two important parameters that affect the photometric and spectral behavior of planetary surfaces in telescopic and spacecraft data. We have derived photometric and spectral phase functions for the Asteroid 4 Vesta, the first target of the Dawn mission, using ground-based telescopes operating at visible and near-infrared wavelengths (0.4-2.5μm). Photometric lightcurve observations of Vesta were conducted on 15 nights at a phase angle range of 3.8-25.7° using duplicates of the seven narrowband Dawn Framing Camera filters (0.4-1.0μm). Rotationally resolved visible (0.4-0.7μm) and near-IR spectral observations (0.7-2.5μm) were obtained on four nights over a similar phase angle range. Our Vesta photometric observations suggest the phase slope is between 0.019 and 0.029. mag/deg. The G parameter ranges from 0.22 to 0.37 consistent with previous results (e.g., Lagerkvist, C.-I., Magnusson, P., Williams, I.P., Buontempo, M.E., Argyle, R.W., Morrison, L.V. [1992]. Astron. Astrophys. Suppl. Ser. 94, 43-71; Piironen, J., Magnusson, P., Lagerkvist, C.-I., Williams, I.P., Buontempo, M.E., Morrison, L.V. [1997]. Astron. Astrophys. Suppl. Ser. 121, 489-497; Hasegawa, S. et al. [2009]. Lunar Planet. Sci. 40. ID 1503) within the uncertainty. We found that in the phase angle range of 0°<.α≤. 25° for every 10° increase in phase angle Vesta's visible slope (0.5-0.7μm) increases 20%, Band I and Band II depths increase 2.35% and 1.5% respectively, and the BAR value increase 0.30. Phase angle spectral measurements of the eucrite Moama in the lab show a decrease in Band I and Band II depths and BAR from the lowest phase angle 13° to 30°, followed by possible small increases up to 90°, and then a dramatic drop between 90° and 120° phase angle. Temperature-induced spectral effects shift the Band I and II centers of the pyroxene bands to longer wavelengths with increasing temperature. We have derived new correction equations using a temperature series (80-400. K) of HED meteorite spectra that will enable interpretation of telescopic and spacecraft spectral data using laboratory calibrations at room temperature (300. K).
KW - Asteroid Vesta
KW - Asteroids, Composition
KW - Infrared observations
KW - Photometry
KW - Spectroscopy
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U2 - 10.1016/j.icarus.2011.10.010
DO - 10.1016/j.icarus.2011.10.010
M3 - Article
AN - SCOPUS:84455212153
SN - 0019-1035
VL - 217
SP - 153
EP - 168
JO - Icarus
JF - Icarus
IS - 1
ER -