The light curve is extremely strange; it becomes brightest about 145
days after the perihelion passage. It was discovered in 1989 when it
has already passed a half year after the perihelion passage, that is
because this peculiarity.
Kazuo Kinoshita's calculation revealed that it passed close by Jupiter
in 1984 and the perihelion distance reduced from 3.25 A.U. down to
2.65 A.U. It became closest to the sun during several hundred years,
and it was discovered.
The maximum brightness has been fading by 1 mag in every appearance
during last three appearances in 1988, 1996 and 2004. But the strange
light curve, the comet becomes brightest about 145 days after the
perihelion passage, did not change.
Kazuo Kinoshita's calculation revealed that it will pass close by
Jupiter again in 2008, and the perihelion distance increases
drastically up to 3.75 A.U. So it will be extremely faint, fainter
than 19 mag at best, after the next return in 2013.
In spite of its asymmetric light curve, no non-gravitational effect is
found in Kazuo Kinoshita's calculation.