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From: starrfie@hydro.la.asu.edu (Sumner Starrfield)
Subject: Re: Comet/Jupiter Collision FAQ
Date: Tue, 30 Nov 93 11:41:22 MST
>Q2.4: Where will the comet fragments collide on Jupiter?
> All components of the comet will hit on the dark farside of Jupiter,
>out of sight from Earth. The impact sites will be around 45 degrees
>South at a point roughly 35 degrees east (toward the sunrise terminator)
>from the midnight meridian. About 1.5 hours after each hit, the impact
>points will rotate into view as seen from Earth [1].
More precisely, the impact of the center of the comet train is predicted to
occur at -37 degrees Jupiter latitude at a Sun-comet-Jupiter angle of 51
degrees on the morning side of the planet. (Source: David Seal from JPL).
>Q2.5: What will be the effect of the collision?
Kevin Zahnle from JPL predicts that each comet fragment will explode
into a fireball about 200 km below the cloudtops of Jupiter. The
fireball will initially be hidden underneath the cloudtops but will
expand rapidly with the plume material rising to about 1.02 to 1.25
Jupiter radii above the cloudtops. The temperature of the fireball may
reach up to 30,000 degrees C with a luminosity of 4x to 25x the brightness
of Jupiter.
>Q2.7: Will Hubble, Galileo or Voyager be able to image the collision?
> Even though Voyager II will have a direct view of the impacts, the probe
>will be so far away that Jupiter will appear only as a pixel on the images.
>This does not mean, however, that useful data cannot be obtained from this
>probe.
The comet collisions are visible from both Voyager 1 and Voyager 2.
Voyager 1 will be 52 AU from Jupiter and will have a near-limb observation
viewpoint. Voyager 2 will be in a better position to view the collision from
a perspective of looking directly down on the impacts, and it is also
closer at 41 AU. Jupiter will appear as 2.5 pixels from Voyager 2's
viewpoint and 2.0 pixels for Voyager 1. If there is any imaging to be
done by Voyager, it will only be by Voyager 2.
> The impacts will occur on the limb of Jupiter as seen from the Galileo
>Space Probe. However, due to antenna troubles the data transfer rate
>back to Earth is slow and as a result the onboard computer will still
>have data from the Ida (asteroid) encounter. Either some of the Ida
>images will need to be erased or some of the Jupiter/comet observations
>will need to be omitted.
The Ida data playback is scheduled to end at the end of June, so there should
be no tape recorder conflicts with observing the comet fragments colliding
with Jupiter. The problem is how to get the most data played back when Galileo
will only be transmitting at 10 bps. One solution is to have both Voyager 2
and Galileo record the event and and store the data on their respective
tape recorders. The Voyager 2 data will be played back first at something
like 3500 bps. The images will be small, but at least the time of each
comet fragment impact can be determined. Using this information, data
can be selectively played back from Galileo's tape recorder. From Galileo's
perspective, Jupiter will be 60 pixels wide and the impacts would only show
up at about 1 pixel, but valuable science data can still collected in the
visible and IR spectrum along with radio wave emissions from the impacts.
The imaging of the comet impacts by Voyager and Galileo has not
been officially approved yet, but from what I hear it looks very likely.
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ Galileo S-Band | "Why must hailstones always
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | be the size of something
|_____|/ |_|/ |_____|/ | else?" George Carlin
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