9522568 Campins A unique opportunity to study a particularly interesting comet, 2060 Chiron, is at hand. Comet Chiron is now near perihelion (February 1996) and will be at its brightest in 51 years. Simultaneously, the European Space Agency's Infrared Space Observatory (ISO), which is scheduled for launch in September 1995, will be making observations of Chiron during its 18-month mission. A coordinated ground-based and space-based study of Chiron, and two other comets, will be carried out. The combination of frequent ground-based, and high sensitivity space-based, infrared wavelength observations, will yield extensive information about these three comets. The ISO observing time for these comets has already been assigned to the team. The following items describe the main goals of the research. 1. Characterization of Chiron's variability in the infrared wavelength region of the electromagnetic spectrum. The usefulness of ground-based observations in support of ISO arises mostly because the time assigned on the ISO satellite to observe Chiron (and most other targets) is not sufficiently long to characterize their infrared variability, and observing time by the ISO satellite will be spent mainly obtaining observations which are not possible using ground-based telescopes. 2. Theoretical thermal models of Chiron's nucleus will be tested. a.) Thermal-infrared observations of Chiron's nucleus before and after opposition can reveal which of those geometries presents the cooler morning terminator, and hence distinguish between prograde and retrograde rotation by detecting temperature changes. b.) Frequent observations before and after perihelion can be used as a diagnostic of a number of nuclear characteristics, including the pole orientation. 3. Observations of secondary targets. Similar, but necessarily less detailed studies of Comets d'Arrest and Kopff, will be carried out. These two comets will also be observed by ISO, and will b e well placed for observations in 1995-1996.
