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]
                  [E-mail: cchapman@psi.edu]

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 
   imaging

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). 

NASA Official: Ed Grayzeck, edwin.j.grayzeck@nasa.gov
Last Updated: 06 January 2005, DRW