THE INFRARED LIGHT-CURVE OF PERIODIC COMET HALLEY 1986-III AND ITS RELATIONSHIP TO THE VISUAL LIGHT-CURVE, C2, AND WATER PRODUCTION-RATES

The near-infrared light curve of Periodic Comet Halley 1986 III is analyzed and compared with C2 production, water production, and the visual light curve. This is the most complete infrared light curve compiled, to date, for any comet. The scattering phase function at small Sun-comet-Earth angles is shown to affect the slope of near-infrared light curve significantly. P/Halley's dust production, as inferred from the infrared light curve, did not vary as a simple power-law with respect to heliocentric distance, but showed an increased production rate near perihelion which appears to be correlated with the onset of significant jet activity. The near-infrared light curve, visual light curve, C2, and water production rates displayed different heliocentric variations suggesting that one parameter cannot be accurately estimated from another. This is particularly true of the early preperihelion visual light curve which reflects the accumulation of material in the growing coma and, thus, does not mimic the heliocentric variation of any of the other parameters. During short-term periods of enhanced activity, on the time scale of hours, the small aperture (near-nucleus) observations peaked within hours of the onset of activity. A peak of 0.3-0.5 magnitude in the visual magnitude, representing the integrated brightness of the comet's visible coma, lagged the other parameters by about a day. The near-infrared color, J-H, was less red during periods of strong dust activity.