Photometric and spectroscopic observations of (132524) 2002 JF₅₆: fly-by target of the New Horizons mission^*

¹ Max Planck Institute for Solar System Research, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany e-mail: [tubiana;duffard;boehnhardt]@mps.mpg.de
² Universidad Metropolitana de Ciencias de la Educación, Santiago, Chile e-mail: lbarrera@umce.cl

Received: 6 October 2006
Accepted: 14 November 2006

Abstract

Aims.The asteroid (132524) 2002 JF₅₆ was the distant fly-by target of the New Horizons spacecraft on June 13, 2006. To further enhance our knowledge of this asteroid and facilitate the cross-calibration of the spacecraft instruments, ground based observations of the asteroid were performed in May 2006 at ESO VLT.

Methods.Photometry and spectroscopy of (132524) 2002 JF₅₆ were performed: a set of R filter broadband images and reflectance spectra were taken with FORS2 of the ESO VLT for a total of three nights (May 25, 30 and 31, 2006). Each observational cycle spans a time interval of about one hour per night. The observations were performed about two weeks before the fly-by, when the asteroid was at a heliocentric distance of 2.5 AU.

Results.The reflectance spectra of 2002 JF₅₆ resemble those of S-type asteroids. From the photometry of the asteroid, an effective diameter of about 2.3 km is estimated and a lower limit for the axis-ratio of (1.19 ± 0.02) is determined.