Mon Jul 25 05:19:10 1994
In re-examining our Jupiter data, we have identified
what appears to be a prompt flash from the V impact
on July 22. In a continuous series of 10 sec exposures
at 2.30 microns (FWHM = 0.16 microns), the flash
was first observed in the frame starting at 4:23:04.1 UTC
(+/- 0.5 s), and has a total duration of 50 sec.
The maximum flux was measured at 2% (0.02) of the total
brightness of impact site Q1 in the same frame, and this
signal level was observed in two successive frames. The
SNR is 50:1, based on flux variations in adjacent frames.
The flash declined steeply to the background level in the
following 3 frames. We estimate the start time of the flash,
if it was abrupt, at 4:23:03 UTC, or 7 minutes after the
prediction of Chodas & Yeomans of July 20.
The image is pointlike, with a FWHM of 0.6 arcsec, and is located within 0.25 arcsec of the terminator, which differs by approx. 0.2 arcsec from the geometric limb. The flash image appears on top of a fainter image which we believe to be site E beginning to rotate onto the limb. The 'E' image is comparable in brightness to the flash signal, but varies very little between frames (+/- 2%). Impact sites H, Q1, R, G and L are visible in the same frame.
The observations were made on the 200-inch Hale telescope at Palomar Observatory, with a 256*256 InSb camera. Simultaneous data collected at 5 microns have not yet been analyzed.
The Palomar Caltech-Cornell comet crash team:
Phil Nicholson, Gerry Neugebauer, Alycia Weinberger, Keith Matthews, Tom Hayward, Colleen McGhee, Jeff VanCleve, John Miles and Dave Shupe.
25 July 1994.