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Galileo Imaging Plans


                           M E M O R A N D U M

To:         SL-9 Observers

From:       Clark R. Chapman
            Planetary Science Inst./SAIC
            620 N. 6th Ave.
            Tucson, AZ  85705  USA
                  [Phone: 602-622-6300; FAX: 602-622-8060]

Date:       8 July 1994

Subject:    Galileo Imaging Plans

The Galileo sequence that contains the observations of Comet SL-9's impact with Jupiter has been completed, approved, and transmitted to the spacecraft, according to the cognizant JPL specialist, Catherine Heffernan. The July 5th updates by Chodas and Yeomans were used to develop "tweaks" to the times that we will be recording data to tape. (The shutter will be operated for about 2 hours around each of the 6 events we are observing, but only about one hour of data will be recorded on tape for each event...the tweaks have updated the record times from those we estimated earlier.)

The table below gives impact times and observation times for the 6 events that will be imaged by the camera, and indicates the type of observation (we are using 4 different modes).

All times are in Spacecraft Event Time -- UTC (these are EARLIER than times observed on Earth!). Fragment, type impact time 1 sigma observation time

                                            (min)        start     stop
------------------------  ----------       -------       ----------------
D, 8x8 start/stop mosaic  7/17 11:12:27      8.7         10:45     11:48
   8 2/3-second imaging   

E, 8x8 start/stop mosaic  7/17 14:34:26      8.0         14:05     15:08
   8 2/3-second imaging 

K, diagonal slew          7/19 09:48:17      6.5          9:21     10:24
   30 1/3-sec imaging 

N, diagonal slew          7/20 09:48:47      8.6          9:26     10:29
   30 1/3-sec imaging 

V, horizontal slew        7/22 03:27:20     12.4          2:54      3:57
   30 1/3-sec imaging 

W, 8x8 continuous slew    7/22 07:23:09      9.1          6:51      7:55
   mosaic, 2 1/3-second 

By July 22nd, the imaging team must deliver to the Galileo Project the starting point for a jailbar search for events D, E, K, and N. This will depend critically on information downlinked by the Galileo PPR instrument for events B, H, and L and on ANY AND ALL INDICATIONS FROM GROUNDBASED OBSERVERS ABOUT WHEN IMPACT AND OTHER OPTICALLY IMPORTANT PHENOMENA ASSOCIATED WITH EVENTS D, E, K, AND N (and later for V and W) MAY HAVE OCCURRED. The first jailbar data will be downlinked and analyzed by the first few days in August, on the basis of which we will uplink the parameters to acquire the 75-line swaths of data from event D. A similar process continues through August and September for the other impacts we observed. It is anticipated that we will receive our first real data by about mid-August.

We are optimistic that we can detect the impacts of SL-9 fragments, even if the comet has "fizzled" (from the perspective of Earth-based observers) into a meteor storm. Naturally, we hope for the complete range of bolide and fireball phenomena that may shed the maximum amount of light on Jupiter's chemistry, atmospheric dynamics, and so on.

I have been leading the imaging team's SL-9 science investigation. The other cognizant members of the imaging team are Team Leader Mike Belton, Andy Ingersoll, and Joe Veverka. We would welcome comments and questions from our colleagues...and any reliable information that you have that will help narrow our uncertainties about where we are most likely to find our direct imaging of the impact sites on our tape recorder (i.e. impact times for D, E, K, N, V, and W).

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