28 research outputs found
Outgassing Behavior of C/2012 S1 (ISON) From September 2011 to June 2013
We report photometric observations for comet C/2012 S1 (ISON) obtained during
the time period immediately after discovery (r=6.28 AU) until it moved into
solar conjunction in mid-2013 June using the UH2.2m, and Gemini North 8-m
telescopes on Mauna Kea, the Lowell 1.8m in Flagstaff, the Calar Alto 1.2m
telescope in Spain, the VYSOS-5 telescopes on Mauna Loa Hawaii and data from
the CARA network. Additional pre-discovery data from the Pan STARRS1 survey
extends the light curve back to 2011 September 30 (r=9.4 AU). The images showed
a similar tail morphology due to small micron sized particles throughout 2013.
Observations at sub-mm wavelengths using the JCMT on 15 nights between 2013
March 9 (r=4.52 AU) and June 16 (r=3.35 AU) were used to search for CO and HCN
rotation lines. No gas was detected, with upper limits for CO ranging between
(3.5-4.5)E27 molec/s. Combined with published water production rate estimates
we have generated ice sublimation models consistent with the photometric light
curve. The inbound light curve is likely controlled by sublimation of CO2. At
these distances water is not a strong contributor to the outgassing. We also
infer that there was a long slow outburst of activity beginning in late 2011
peaking in mid-2013 January (r~5 AU) at which point the activity decreased
again through 2013 June. We suggest that this outburst was driven by CO
injecting large water ice grains into the coma. Observations as the comet came
out of solar conjunction seem to confirm our models.Comment: 8 pages, 2 figures, 3 table
Effects of dust layers on thermal Emission from airless bodies
: We have investigated the influence of thin thermally opaque dust layers on the thermal emission of rocks and regolith and determined the thermal response of these dust-covered surfaces to diurnal insolation cycles. Results are computed for Hayabusa2âs target asteroid (162173) Ryugu, which was observed by thermal infrared instruments on the orbiter and in situ. We show that even a very thin (10..100âÎŒm) fine-grained porous dust layer with thermal inertia of 25âJâmâ2âKâ1âsâ1/2 can have a significant influence on surface temperatures and alter the apparent thermal inertia of the underlying material derived under the simplified assumption of a homogenous half space by more than 20%. The masking of the underlying material is complete at about 1 diurnal skin depth, corresponding to ~â10âmm on Ryugu. Between 0.1 and 1 diurnal skin depths, we find a thermal lag smaller than what would be predicted for a surface consisting of dust only
Thermal properties of comet 67P derived from Rosetta/VIRTIS, and orbital observations of Philae landing site
International audienc
Thermal Maps and Properties of Comet 67P as Derived from Rosetta/VIRTIS Data
International audienc
Thermal Maps and Properties of Comet 67P as Derived from Rosetta/VIRTIS Data
International audienc
VIRTIS-Rosetta observations of the nucleus of 67P/Churyumov-Gerasimenko during the Comet Characterisation phase (July-August 2014)
International audienc
Thermal Maps and Properties of Comet 67P as Derived from Rosetta/VIRTIS Data
International audienc
Thermal Maps and Properties of Comet 67P as Derived from Rosetta/VIRTIS Data
International audienc
VIRTIS-Rosetta observations of the nucleus of 67P/Churyumov-Gerasimenko during the Comet Characterisation phase (July-August 2014)
International audienc