Bibcode
Meech, Karen Jean; Hainaut, O.; Weaver, H. A.; Snodgrass, C.; Pittichova, J.; Pittichova, J.; Riesen, T.; Vilas, F.; A'Hearn, M. F.; Licandro, J.; Gulbis, A.; Lowry, S.
Referencia bibliográfica
American Astronomical Society, DPS meeting #41, #20.07
Fecha de publicación:
9
2009
Número de citas
0
Número de citas referidas
0
Descripción
With the recovery of comet 103P/Hartley 2, the target of the EPOXI
mission, we have begun the characterization of the nucleus necessary for
the mission. Observations from past apparitions of this comet show that
it typically begins activity while far from the sun, near r = 4 AU
(about 450 days pre-perihelion). This makes obtaining information about
the nucleus very challenging, because the comet is small and thus faint
(near mag 25) just before activity begins. The comet was recovered using
the VLT with FORS2 during 2008 using observations obtained at 4 epochs
when the comet was between 5.7-5.5 AU (Snodgrass et al.). Deep composite
images showed evidence of dust, possibly evidence of the dust trail. To
ensure that we could obtain adequate information about the rotation
period for the mission, an international observing campaign was
undertaken with 8-10 m telescopes from March-July 2009. Ten hours were
awarded on the LBT telescope, 28 hours of time on the Gemini N and S
telescopes, 2 nights on the VLT 8m, 7 hrs on the GTC 10.4m and 20 hrs on
the SALT telescope in S. Africa. In addition we received 12 orbits of
HST time, spanning a clock time of 1 day. The comet was very faint in
the HST images, and data were averaged by orbit to create the light
curve. Data from Gemini N and S were obtained on 3 consecutive nights,
under excellent conditions. A preliminary analysis of the Gemini data
suggests a double peaked light curve with a nucleus rotation period near
16.6 hrs, which is consistent with the HST observations. The light curve
shape has uneven maxima and sharp minima, suggesting the nucleus shape
deviates from a triaxial ellipsoid.