A dataset provided by the European Space Agency

Name DDT_lorourke_20
Title Herschel Observations of Comet ISON (C/2012 S1) - the comet of the century


DOI https://doi.org/10.5270/esa-5a1qrrj
Author o.rourke, l.
Description Comet C/2012 S1 (ISON) was discovered in September 2012. Its orbit is nearly parabolic consistent with a dynamically
new comet coming freshly from the Oort cloud. It is peculiar in that it is a sungrazer (q = 0.012AU) although
not of the Kreutz group. This comet is expected to be the brightest comet for decades reaching a magnitude
(according to Horizons) brighter than the full moon at closest approach to the sun. Journalists are calling it the Comet of the century and it is expected to have huge public outreach.

This proposal serves to use the HIFI and PACS instruments to, in the former case, obtain the first detection of H2O from this comet, and in the latter case, derive a size estimate for the
nucleus and determine its dust production rate. A total time of 5 hours (3 h HIFI, 2 h PACS) is being requested.

HIFI is the most powerful instrument to detect water in distant comets, through observation of the fundamental water rotational transition which is much stronger than the transitions observable from the ground. The HIFI
observations allows to detect H2O well outside the water dominated sublimation range (i.e. at heliocentric
distances rh > 3 AU), a rare measurement for a comet. PACS is essential to detect the nucleus,
its coma and any extended dust emission that may exist at that time.

Our measurements will provide an important and unique reference for those wishing to track this comet for
the remainder of the year. Unique in that the detection of early water outgassing from comet ISON can only be
achieved with the Herschel Observatory because of its sensitivity and the spectral resolution o?ered by HIFI to
e?ciently detect H2O. Observations of the H2O strong rotational lines cannot be performed from the ground.
Unique in that we would be detecting the nucleus and dust cloud at 70 microns. These are unique measurements and unique solely to the ...Herschel Space Observatory and the
European Space Agency; ideal for an ESA public outreach campaign.
Publication Herschel and IRAM-30 m observations of comet C/2012 S1 (ISON) at 4.5 AU from the Sun . O'Rourke L. et al. . Astronomy & Astrophysics, Volume 560, id.A101, 7 pp. . 560 . 10.1051\/0004-6361\/201322756 . 2013A&A...560A.101O ,
Instrument HIFI_HifiPoint_fs, PACS_PacsPhoto_largeScan
Temporal Coverage 2013-03-08T01:30:52Z/2013-03-13T20:15:48Z
Version SPG v14.2.0
Mission Description Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
Creator Contact https://support.cosmos.esa.int/h®erschel/
Date Published 2013-09-13T19:47:32Z
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, o.rourke, l., 2013, DDT_lorourke_20, SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-5a1qrrj