Wed Jul 20 01:39:05 1994

The HST imaging team has measured longitudes for Features G and H and has re-measured longitudes for Features A, C, and E. We use images from the PC and from the WF when the feature is reasonbly close to the central meridian. We have had several people check each other's results: we have used two separate pieces of software: AMIE (Chris Barnet - York Univ.) and an IDL variation (John Clarke - Univ. Michigan). We use the bright limb to determine the planet center, and we check internal consistency by comparing feature locations in different images. We believe these longitudes are accurate to plus or minus 1.5 degrees. The longitudes refer to the northwest part of the dark feature at each impact site (see press release photos of site A or G).

Feature		Obs. 		Pred. 		Delay		Time

A		185		178		11.6		20:11
C		224		218		 9.9		 7:12
E		154		150		 6.6		15:12
G		 25		 23		 3.3		 7:32
H		101		 96		 8.3		19:34

Here Obs. and Pred. are longitudes in degrees, the latter from Chodas and Yeomans in their 16 July 1994 message. Delay is this difference converted to minutes, and the Time is the estimated time of impact (hh:mm) obtained by adding the Delay to the times estimated by Chodas and Yeomans. These times are accurate provided C & Y know where the impact occurs relative to the Earth-Jupiter-Sun, and the only uncertainty is when the impact occurs. This estimate of the impact times does not need to be corrected for the rise time of the plume, since we do not use the appearance of the plume at the limb in our estimates. Likewise, there is no need to correct for refraction.

Reta Beebe and Andy Ingersoll, for the HST Imaging Team.