DIRECT IMAGING AND SPECTROPHOTOMETRY OF COMET-P TEMPEL-2

Comet P/Tempel 2 was monitored from May to November 1988 with direct imaging and spectrophotometric techniques. The nuclear diameter was determined to be about 10 km. The visual lightcurve of the comet in 1988 showed an unusual steep increase preperihelion (n = 30.0), but the normal moderate decrease postperihelion (n = 5.2). The fanlike coma was asymmetrically extended in the solar direction. Both phenomena can be explained-at least qualitatively-by the spin-vector model for comet P/Tempel 2 published by Z. Sekanina in 1987 (ESA SP-278, pp. 315-336). Preliminary gas production rates (Q) of the comet in late October/early November 1988 were derived from the spectra, i.e., Q(CN) = 2.6 × 1026 sec-1, Q(C) = 9.4 × 1025 sec-1, Q(C) = 8 × 1024 sec-1. From the flux ratio of the Δν = 1 to the Δν = 0 transition in the Swan bands of P/Tempel 2, the transition moment between the lowest electronic triplet state and the lowest singlet level of C2 was estimated to be 2 × 10-6 (in atomic units). © 1990.