Data Set Information
DATA_SET_NAME POLARIMETRY OF ASTEROID ITOKAWA V1.0
DATA_SET_ID EAR-A-I0066-3-ITOKAWAPOL-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set contains the polarimetry of asteroid 25143 Itokawa published in Cellino et al. (2005). The observations were made from June 26 through July 3, 2004 with the Torino photopolarimeter at the 2.15 m telescope of the El Leoncito Observatory in Argentina. On June 26 and July 1 and 2, weather prevented any useful observations of Itokawa, so the data presented here are from the other nights of the run. The degree of linear polarization in five filters (Johnson-Cousins UBVRI) was measured over a wide range of phase angles, between 40 and 80 degrees. The data obtained are sufficient to derive an estimate of the asteroid's geometric albedo of 0.24 +/- 0.01. The single entries in the table correspond to averages over time spans of about one hour each. Some averaging was done because in polarimetry single measurements have usually fairly large error bars. During one hour the phase angle did not change by more than one degree, as can be seen from the difference in the phase angle listed in each entry of the table for the same night. Single polarization measurements consisted of eight photometric measurements corresponding to a cycle of eight different positions of the half-wave plate in front of the polarimeter. A single cycle takes about 3.5 minutes. For Itokawa it was decided that the usual procedure of computing the average nightly polarization, by making an average over all the single measurements taken during the night, was clearly not appropriate. The reason for not doing so was that the object was moving fast and the phase angle was changing. On the other hand, the phase change was fairly small over intervals of some tens of minutes. The average over the cycles continuously executed during time spans of about one hour was adopted as a compromise between the need of documenting the change in polarization for changing phase angle, and the need of having fairly good error bars in the corresponding polarization measurements. 25143 Itokawa is an S-type asteroid, an NEO, and was the target of the Hayabusa mission. Cellino, A., F. Yoshido, E. Anderlucci, P. Bendjoya, M. DiMartino, M. Ishiguro, A.M. Nakamura, and J. Saito, A polarimetric study of asteroid 25143 Itokawa, Icarus 179, 297-303, 2005.
DATA_SET_RELEASE_DATE 2007-05-24T00:00:00.000Z
START_TIME 2004-06-28T09:32:24.000Z
STOP_TIME 2004-07-04T08:02:24.000Z
MISSION_NAME SUPPORT ARCHIVES
MISSION_START_DATE 2004-03-22T12:00:00.000Z
MISSION_STOP_DATE N/A (ongoing)
TARGET_NAME 25143 ITOKAWA
TARGET_TYPE ASTEROID
INSTRUMENT_HOST_ID OBS007T1
INSTRUMENT_NAME TORINO PHOTOPOLARIMETER
INSTRUMENT_ID I0066
INSTRUMENT_TYPE POLARIMETER
NODE_NAME Small Bodies
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : Uncertainties for the measurements are given in the table. Note that albedo was determined by linear extrapolation of the polarization obtained within the phase angles 40-80 degrees, rather than near the inversion point (20-30 degrees). For further information about the measurements and analysis, see Cellino et al. (2005).
CITATION_DESCRIPTION Cellino, A., Yoshida, F., Anderlucci, E., Bendjoya, P., DiMartino, M., Ishiguro, M., Nakamura, A.M., and Saito, J., Polarimetry of Asteroid Itokawa V1.0. EAR-A-I0066-3-ITOKAWAPOL-V1.0. NASA Planetary Data System, 2007.
ABSTRACT_TEXT This data set contains the polarimetry of asteroid 25143 Itokawa published in Cellino et al. (2005). The observations were made from June 26 through July 3, 2004 with the Torino photopolarimeter at the 2.15 m telescope of the El Leoncito Observatory in Argentina. The degree of linear polarization was measured in five filters (Johnson-Cousins UBVRI).
PRODUCER_FULL_NAME CAROL NEESE
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