[Forwarded from Paul Chodas, JPL]
Here's the last edition of our Predicted Impact Parameters table before the impacts begin.
The impact times are within a few minutes of those in our previous table, dated July 11. In particular, the time for A is 2.1 minutes later, and C and F are 2.7 minutes later. The time for U moved 4 minutes earlier.
We have removed the satellite data from this table, as it was changing little from one solution to the next. In its place, we give the date of the last data point used in our orbit solutions. As you can see, despite heroic efforts, observers were unable to image fragments A and B later than July 13.
The impact time uncertainties for most of the fragments are now down in the 3-5 minute range (1-sigma). Please use at least +/- 2 sigmas for your observing windows. Also note that these predictions refer to the central condensation of each fragment.
Paul Chodas 1994 July 16 16:20 UT
P.W. Chodas, D.K. Yeomans (JPL/Caltech)
Predictions as of 1994 July 16
Date of last astrometric data in these solutions: 1994 July 14
The predictions for all fragments except Q2 are based on independent orbit solutions; our orbit reference identifier is given. The orbit solution for fragment Q2 was obtained by applying a disruption model to the orbit for Q1, and using astrometric measurements of Q2 relative to Q1.
Immediately to the right of the predicted impact times, we give the 1-sigma uncertainties in those times for all fragments except Q2. We have made an effort to make these uncertainties realistic: they are not formal uncertainty values. NOTE: To obtain a 95% confidence level, one should use a +/- 2 sigma window around the predicted impact time. The uncertainties for fragment Q2 have not been quantified, but are probably comparable to those for T.
The dynamical model used for these predictions includes perturbations due to the Sun, planets, Galilean satellites and the oblateness of Jupiter. The planetary ephemeris used was DE245.
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Fragment Impact 1-sig Jovicentric Meridian Angle Orbit Date of
Date/Time Unc. Lat. Long. Angle E-J-F Ref. Last Data
July (UTC) (min) (deg) (deg) (deg) (deg) (July UT)
--------------h--m--s----------------------------------------------------------
A = 21 16 19:59:40 5.5 -43.13 178 64.48 98.72 A25 13.0
B = 20 17 02:54:13 4.1 -43.16 70 63.82 99.18 B20 13.2
C = 19 17 07:02:14 3.7 -43.37 218 65.24 98.12 C18 14.0
D = 18 17 11:47:00 4.7 -43.45 30 65.58 97.85 D19 14.0
E = 17 17 15:05:31 3.1 -43.47 150 65.76 97.72 E35 14.2
F = 16 18 00:29:21 4.0 -43.56 132 64.52 98.57 F26 13.2
G = 15 18 07:28:32 3.1 -43.59 23 66.63 97.07 G32 14.2
H = 14 18 19:25:53 3.1 -43.73 96 66.83 96.89 H31 14.2
K = 12 19 10:18:32 3.1 -43.80 275 67.76 96.21 K33 15.0
L = 11 19 22:08:53 3.4 -43.91 344 68.18 95.88 L34 15.0
N = 9 20 10:20:02 4.9 -44.29 66 67.77 96.10 N22 15.0
P2= 8b 20 15:11:55 4.6 -44.61 244 66.68 96.80 P20 15.0
Q2= 7b 20 19:31:43 -44.35 39 68.78 95.37
Q1= 7a 20 19:59:10 4.5 -44.06 55 69.20 95.12 Q37 15.0
R = 6 21 05:25:56 4.6 -44.07 37 69.44 94.94 R32 15.0
S = 5 21 15:10:22 4.4 -44.16 30 69.80 94.67 S42 15.0
T = 4 21 18:03:45 11.5 -44.99 137 67.34 96.26 T16 4.1
U = 3 21 21:48:30 12.8 -44.43 272 68.81 95.33 U17 8.0
V = 2 22 04:16:53 8.1 -44.43 146 69.50 94.83 V18 15.0
W = 1 22 07:57:36 5.2 -44.15 278 70.44 94.21 W33 15.0
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Notes:
1. Fragments J=13, M=10, and P1=8a are omitted because they have faded from
view. The March'94 HST images show that P2=8b and G=15 have split; we do
not have sufficient data to obtain independent predictions for the
sub-components.
2. The impact date/time is the time the impact would be seen at the Earth, if
the limb of Jupiter were not in the way (i.e., the time listed is the time
of impact plus the light travel time to the Earth); the date is the day in
July 1994; The impact time uncertainty is a 1-sigma value in minutes.
3. The impact latitude is Jovicentric (latitude measured at the center of
Jupiter); the Jovigraphic latitudes are about 3.84 deg more negative.
4. The impact longitude is System III, measured westwards on the planet.
5. The meridian angle is the Jovicentric longitude of impact measured from
the midnight meridian towards the morning terminator. This relative
longitude is known much more accurately than the absolute longitude.
At the latitude of the impacts, the Earth limb is at meridian angle 76 deg
and the terminator is at meridian angle 87 deg.
6. Angle E-J-F is the Earth-Jupiter-Fragment angle at impact; values greater
than 90 deg indicate a farside impact. All impacts will be just on the
farside as viewed from Earth; later impacts will be closer to the limb.
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