A Multi-wavelength study with the ESO VLT of comet 103P/Hartley2 at the time of the EPOXI encounter

We report on simultaneous optical and infrared spectroscopic observations of the Jupiter Family comet 103P/Hartley2 performed with the UT-1 and UT-2 8-m Unit Telescopes of the ESO Very Large Telescope (VLT). These coordinated observations were carried on during several nights (2010 Nov. 5, 9, 10 and 11 UT) around the NASA EPOXI encounter with the comet on Nov. 4 [1] and in support to the key program « Water and related chemistry in the Solar System » (HssO) [2] of the Herschel Space Observatory. From high resolution optical spectroscopy of the CN (0,0) 388 nm band using UVES at UT2 we determined the isotopic ratios 12C/13C = 95 ± 15 and 14N/15N = 155 ± 25 in the CN radical. From the NH2 (0,9,0) and the H2O+ bands around 600 nm, we derived a nuclear spin temperature of 33 ± 3 K for NH3 and 36 +7/-6 K for H2O. These values are similar to those found in Oort- Cloud and Jupiter Family comets. From lowresolution long-slit spectroscopy with FORS2 at UT1 we will determine the CN, C2 and C3 spatial profiles and their production rates. From the high-resolution near-IR spectra that we collected with CRIRES at UT1 we will measure simultaneously the production rates and mixing ratios of the parent molecules H2O, HCN, C2H6, and CH3OH that are well detected in our spectra and we will study the link to the daughter species.