The orbit is almost circular with an eccentricity of about 0.2.
However, it tends to be brightest long time after the perihelion
In the apparition in 1997, it reached to the maximum brightness nearly
one year after the perihelion passage. At the discovery in 1989, it
was already two years since the perihelion passage in 1987 October.
Kazuo Kinoshita's calculation revealed that the comet has passed close
down to 0.68 A.U. to Jupiter in 2002 after the two apparitions, and
the perihelion distance was reduced from 3.7 A.U. down to 3.0 A.U.
In the next return in 2005, it became brightest about 5 months after
the perihelion passage. The difference between the perihelion passage
and the brightest day was reduced because the comet came to approach
closer to the sun. But the asymmetric light curve trend to the
perihelion passage still remains.
Kazuo Kinoshita's calculation revealed that the comet will pass near
by Jupiter twice at the end of 21st century, and the perihelion
distance will be changed drastically. But it keeps the current orbit
until that time.