The following document lists the file abstract/EGRUEN_TOOCOM_2.abs
from catalogue VI/111.
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==> In this proposal, more time is being requested for EGRUEN.TOOCOMBR Comets comprise the most primitive material in the solar system. Observations of their composition are diagnostic of the environment in the early stage where the planets and other solar system bodies were formed. Long-period comets may comprise even more primitive material than short-period comets. Several short- periodic comets (P/Kopff, P/Schwassmann-Wachmann 1, and 2060 Chiron are among the ISO guaranteed time targets (see further below). In contrary to them, Comet C/1995 O1 (Hale-Bopp), discovered on July,22 1995, is a long- period comet, (but not a "new" comet in the Oort's classification) and its previous orbital period is estimated between 3400 and 4200 years. A typical long-periodic comet (e.g. with high eccentricity) is still missing. As a Target of Opportunity an "Anonymous" new comet offers several unique possibilities both for infrared spectroscopy and photometry: Comparison of the characteristics of the dust component in "new" comets with those of short periodical comets. It is suggested, that the surface of a new comet is less processed by solar radiation heating during the perihelion passages and more pristine material will be ejected into the dust coma. Since there are about new 15 comets discovered per year, there is a good chance that a moderate bright long-period (or "new" comet in the Oort's definition) will be observable during the life time of ISO. Therefore an "Anonymous" comet should be a Target of Opportunity, in the case such comet will be discovered early enough before the end of the ISO mission (nominally January, 1st 1998). A typical example is the new comet C/1996 Q1 (Tabur), discovered on August,19th 1996. It should be noted, that this comet could be a potential ToO comet, due to its visibility over the revolutions 434 till 479. The brightness of this comet may be comparable, or even larger, to that of P/Kopff taking the geocentric distance ( 1.7 AU) and the heliocentric distance (1.6 up to 2.3 AU) into account.