Palomar observations of the R impact of comet Shoemaker-Levy 9: I. Light curves

We present near-infrared observations from Palomar observatory of the impact of fragment R of comet Shoemaker-Levy 9 with Jupiter on 21 July 1994. Two instruments were used to image the event at 3.2 and 4.5 microns simultaneously. The lightcurves from these image sequences both show two faint precursor flashes, a bright main peak, and several oscillations over the following hour. We identify the precursor flashes with the entry of the bolide into Jupiter's upper atmosphere, and with the post-impact ejecta plume rising above the planet’s limb. The main peak is due to the re-entry of the collapsing plume into Jupiter's atmosphere and the resultant shock heating.