We are continuing to use the InfraRed Imaging Spectrometer (IRIS) on the 3.9 m Anglo-Australian Telescope (AAT) at Siding Spring Observatory (near Coonabarabran, Australia) to monitor the impacts of the fragments of Comet Shoemaker-Levy 9 with Jupiter. On 19 July, observations were initiated at 06:00 UT, and continued until Jupiter reached the zenith limit of the telescope (13:20 UT). The sky was clear, and the seeing was near 1 arcsec. At the start of observations, the impact sites of fragments G, H, F, E, and A were clearly visible as bright clouds at K-band wavelengths within strong methane bands. These features were also visible as dark features on our guiding TV, which was using a 0.55 micron filter.
The impact flash of S-L 9 fragment K was first detected on the morning limb of Jupiter at 10:24 UT. There was no evidence of the predicted reflection from Europa, which was in eclipse, but visible from the Earth. Images extracted from IRIS K-grism cubes at wavelengths near 2.34 microns revealed an initial flash whose intensity was comparable to that of the fragment G impact flash observed at 7:40 UT on 18 July. The K impact flash reached its maximum brightness at 10:33 UT, when it was about 400 times as bright as the south polar hood. The brightness of this impact site then decreased to about 10 times that of the south polar hood within about 20 minutes, as it rotated onto the disk of Jupiter. The apparent size of the impact site at 2.3 microns was comparable to that of the Great Red spot. The K impact site was also seen as a dark feature at visible wavelengths in the TV guiding camera.