The following document lists the file abstract/JCROVISI_COMETS.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
SCIENTIFIC ABSTRACT
Comets are believed to retain most of the original content of the pristine
Solar Nebula. Therefore, their study provides a unique way to understand
the history of our Solar System and its relation to the interstellar
medium.
We propose to observe one or two periodic comets within the ISO central
program. The primary goals are to investigate the dust and gas compositions
of these objects, to probe the molecular excitation mechanisms and the coma
physical conditions, to monitor the cometary activity and outgassing
processes as a function of heliocentric distance, to compare the behaviour
of different objects.
The present program concentrates on medium-resolution spectroscopic
observations with LWS and SWS. We propose to observe reference spectra of
the brightest objects in the full spectral range of LWS and SWS.
Observations of specific spectral ranges dedicated to the water, CO2 and CO
bands are also planned. For a launch in Nov. 1995, the most suitable
periodic comet during ISO's planned life seems to be P/Kopff, which we plan
to observe at different periods to study its evolution. In the case of a
launch in May 1996, an additional target is P/Wild 2.
This proposal is complementary to other CP cometary proposals to be done
with CAM and PHT.
OBSERVATION SUMMARY
Cometary observations are highly time-dependent. The following targets and
observing periods were selected in function of the expected comet activity
and of the instrument Sun and Earth constraints.
Target list and special requirements:
For a launch in autumn 1995:
- P/Kopff in Apr. 1996 (best period before perihelion: delta = 1.1 AU,
rh = 1.8 AU; expected Q[gas] = 4.e28 s-1). (#1-7.)
- P/Kopff in Oct. 1996 (best period after perihelion: delta = 1.2 AU,
rh = 1.9 AU; expected Q[gas] = 4.e28 s-1). (#8-14.)
- P/Kopff in Dec. 1996 (repeated observation at a larger heliocentric
distance to see evolution). (#15-17.)
For a launch in spring 1996:
- P/Kopff in Oct. 1996 (best period after perihelion: delta = 1.2 AU,
rh = 1.9 AU; expected Q[gas] = 4.e28 s-1). (#1-7.)
- P/Wild 2 in Apr. 1997 (best period around perihelion: delta = 1.1 AU,
rh = 1.6 AU; expected Q[gas] = 3.e28s-1). (#8-14.)
- P/Kopff in Dec. 1996 (repeated observation at a larger heliocentric
distance to see evolution). (#16-17.)
Spectra to be observed:
- Reference spectra of the full 47-197 micron region with the LWS grating.
We expect to mesure several water rotational lines to probe the excitation
conditions, and to detect several OH lines. The observations will be made
in two parts: one integration on the comet, another one on the same field
one or several days later when the comet has moved ("shadow"), to get the
background continuum. (#1 & 3, 8 & 10, 15 & 16.)
- Reference spectra of the full 2.4-45 micron region with the SWS grating.
(#5 & 6 & 7, 12 & 13 & 14.)
- SWS grating spectra of the 2.600-2.898 micron region: study of the water
bands and of the 2.8 micron unidentified cometary emission. (#2, 9.)
- SWS grating spectra of the 4.051-4.805 micron region: study of the CO2
bands and search for CO and other species. (#4, 11, 17.)