Satgen 220  Comets and Meteors  by GM4IHJ                    12th June 93
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Our September/December 92 visitor Comet Swift-Tuttle has now receeded far
enough from the Sun for its surface to re freeze. This means that its
orbit is unlikely to change because it is no longer "jet propelling "
itself via gas jets from its melting surface. So given that its orbit will
not now change it looks clear that when it next returns in 2116 AD, it
will not hit the earth as some alarmists suggested.

But we have not seen the last of the particles that Swift- Tuttle released
from its surface, and we cross the path of the Swift-Tuttle particle
stream = Meteor stream on 12th August 93 at about 0100 ut. This is of
course the well know Perseids Meteor shower . So Meteor Scatter
communications enthusiasts will hopefully get lots of good meteor pings as
this debris burns up in the Earth's atmosphere, several hours either side
of the shower peak.

Let us hope the Perseids is a good shower again this year , to compensate
us for missing what could well be the Astronomical Comet Hit of this and
several other centuries. Comet Shoemaker-Levy passed very close to the big
planet Jupiter in July 1992. So close in fact that Jupiter's gravity seems
to have pulled it apart. With the result that it is now a string of 20 or
more bright pieces of ice and dust, each one perhaps several Kms in size,
and all caught in a Jupiter orbit.

They will not last long in that orbit. Some or all of the group are
scheduled to hit Jupiter on about July 20th 1994, in what could be a multi
million megaton explosion as big as the the one that hit the Earth ( in
Yucatan Mexico ), 65 million years ago. That one wiped out everything on
the land surface of the Earth including the Dinosaurs. Sparing only our
small mammalian ancestors sheltering in their underground burrows.

The Jupiter -Shoemaker - Levy crash should be quite spectacular, but it
looks as if it will occur on the Jupiter night side out of sight of Earth
watchers. Doubtless Astronomers will be tracking the Shoemaker- Levy bits
carefully from now on, and we should get a clearer prediction of whether
collision is inevitable and where it will occur some time before the
actual event. But what ever happens we will eventually get an enormous
amount of data about this type of massive rare collision, and Jupiters own
meteor scatter communications ops ( if they exist a la Arthur Clarke )
look likely to get more and bigger meteors than they would wish for. 
73 de GM4IHJ @ GB7SAN