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Galileo: First Direct Impact Observations


First direct impact observations: Galileo PPR results for Events B and H

The Photopolarimeter Radiometer on the Galileo spacecraft observed Jupiter for 41 minutes during periods corresponding to earthbased observation times of UTC 198/02:22 to 198/03:03 for B and UTC 199/19:11 to 199/19:52 for H. The PPR has a single field of view that is about 4 times the size of Jupiter. A filter at 945 nm was used for these observations; the sample time was 0.4 sec.

No evidence of the B impact was found. The H impact was seen at UTC 19:31:59. The brightness corresponds to about 2% the brightness of Jupiter itself. The signal rises to peak value in about 2 sec and then decreases over 25 sec to background levels.

Galileo is positioned to see the impact sites directly, at a distance of 240 million km; the phase angle of Jupiter is 51 degrees.

Terry Z. Martin, Leslie K. Tamppari, and I. Claypool            JPL
L. Travis, A. Lacis, and J. Hansen                              GISS, New York

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