Satgen 647  Meteor Scatter Comms  by GM4IHJ  (BID SGEN647) 2001-08-18

We have recently progressed through several stages of increased
understanding of the why, how, when and where of meteor scatter, as a
communications tool.  First we had to learn that meteors appear all
day, any day, but there are peak days and, peak periods of several
days, where meteor numbers are enhanced, repeating around the same
dates each year. With meteors coming from quite different preferred
directions from one shower peak to the next. a few dates later. But
faithfully holding the same headings on the same day , one year to the
next.

Gradually a table of dates and, directions ie parts of the celestial
sphere , has evolved. So we now know when the big annual events of
April, August and November, will be with us. Although there was little
direct evidence until the 1980s , to tell us why this was so. Not
until the connection between comets and meteors was established 20 or
so year ago, did it become clear that comets are for the most part
dirty snowballs, which slowly shed dust as their icy surface melts as
they swing around the Sun on their regular passes through the inner
Solar system before going out back into the cold of the outer solar
system for anything between 4 and 40,000 year, depending on their
orbits. Coming through the inner solar system this way they may cross
the earths orbit inbound and then later cross the other side of the
orbit outbound , if their orbital inclination permits this.

In the 1990s the IRAS Infra Red satellite surprised everyone when it
beautifully confirmed the presence of dust trails, stretching for
millions of miles across the solar system , several of which could be
directly coupled to the orbits of well known comets. With thousands
and millions of years these dust trail gradually disperse. So the
Earth is continuously encountering old comet dust every hour every
day. With maximum capture of dust/potential meterorites taking place
on the morning side of the earth  ie the bow of the earth as it swings
round around its annual orbit of our Sun.

All of which has been common knowledge amongst meteor scatter
communicators. Some of whom use simple letter codes and slow hand
morse to pass messages by reflecting/scattering their signal off the
ionized trails created as meteors burn up in the Earths atmosphere.
While for years now European radio amateurs have gone one better and
used hi speed morse to maximise the message transfer potential. So it
comes as no surprise that several very slick digital meteor scatter
communications systems are now appearing . Best so far seems to be
K1JT's multi tone hispeed digital system called WSJT. For details of
which you can check , ( thanks to GM4JJJ for details ):-
  http://pulsar.princeton.edu/~joe/K1JT
or take a listen around 144.150 MHz. With this system you really can
begin to communicate. Which is great news noting that Astronomers are
now reporting that many other Sun type stars appear to have families
of comets orbiting them. With spectrum analysis of the light received
from them indicating the presence of water. Water which must be
somewhere out from the parent star itself. So where ever your
spaceship and amateur radio takes you , real first class meteor
scatter should be available.