A sequence of orbital elements for the comet Shoemaker-Levy 9 is now available on the Web at http://www.lns.cornell.edu/~seb/celestia/sl9_2.ssc. The file includes four separate orbits, each defined by elements determined closer and closer to the time of impact.
Even so, the last orbit in the file doesn't quite intersect with Jupiter. Gravitational effects resulted in eccentricities greater than 1, but hyperbolic orbits cannot yet be shown by Celestia.
Some comments about the sources of the ephemerides are included in the SSC file as well as on its home page at http://www.lns.cornell.edu/~seb/celestia/