Time series photometric measurements are presented of comet P/Schwassm
ann-Wachmann 1 at a heliocentric distance of 5.886 AU when the comet p
ossessed an extensive coma. The light curve shows a modulation caused
by the rotation of the nucleus. The rotation period is considerably sh
orter than the 5 day period found by Whipple [AJ, 85, 305 (1980)] and
we find substantial evidence that the nucleus may be in a complex spin
state characterized by two periods 14.0 and 32.3 hr. Models of the ra
te at which the rotational light curve range decreases as a function o
f the amount of coma in the aperture have determined that the projecte
d maximum to minimum axis ratio of the comet is 2.6 and that the produ
ct of the albedo times the rotationally averaged nucleus radius size,
p(R)R(N)2 is 9.5 +/- 0.3 km2. Assuming a minimum geometric albedo of p
(R) = 0.04, the maximum projected average nucleus radius is R(N) = 15.
4 +/- 0.2 km, which is only 44% of the size estimated by Roemer [Mem.
Soc. Roy. Sci. Liege, 13, Ser. 5, 23 (1966)]. However, using the albed
o determined by Cruikshank & Brown [Icarus, 56, 377 (1983)] of p = 0.1
3, the nucleus radius is only R(N) = 8.6 +/- 0.1 km. Because of the un
known nucleus orientation, these will be upper limits to the nucleus s
ize. It appears that the nucleus of P/Schwassmann-Wachmann 1 is not th
e large nucleus that it has been believed to be for nearly 40 yr.