Satgen 211    Meteors and Interstellar Dust   by GM4IHJ      10th April 93
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Satgen 180 introduced the ( still awaiting launch ) UNAMSAT-1 . This
Mexican satellite will carry store and forward digigital communications ,
and, a bonus for experimenters in the shape of a 40 MHz Meteor Radar. A
bonus it was suggested which might reveal to us just how much if any of
the meteor dust hitting the upper atmosphere had its origins in distant
star systems far from our own Solar system.
31 weeks later this question posed in Satgen 180 , appears to have been
amplified by some very interesting reports from Ulysees, the European
Space Agencies Solar Probe. Ulysees has recently used a gravity sling shot
manouevre around the giant planet Jupiter to alter its orbit out of the
plane of the Solar system, and thrust it back in towards the Sun on a high
inclination track which will eventually take it over the North and South
Polar regions of our star. Providing us with our first views of regions
which are not observable from the Earth.
It is however , Ulysees's recent flip around Jupiter which has produced an
unexpected surprise. Previous Jupiter probes included two Pioneer craft
and two Voyager craft. But none of them carried sensitive dust and minor
particle detectors, and none of them flew the inclined orbit of Ulysees, 
which makes it easier to distinguish the orbits and speeds of these
particles.
What Ulysees found in Jupiter space was quite unexpected. Not only are
there particles escaping Jupiters massive gravity and escaping from the
planet and its system of moons, but there are also particles travelling
the opposite way to the way the planets orbit the Sun , and doing so at
velocities greater than 26 Kms/sec ie the Solar system escape velocity.
Material travelling through the solar system is not new. It has long been
known that our solar system in riding through a stream of light elements (
mostly helium ) which is coming in from the constellation of Centaurus and
heading out towards Cassiopeia. What is different now, is that the
material encountered by Ulysees is dust ( collections of millions of atoms
), with small but measurable mass, moving at Solar system escape velocity.
Just how much if any of this material gets in to the Earth we may discover
with UNamsat-1. The problem of sorting out true particle velocity from a
reading of radar doppler shift , and satellite velocity , or earth
velocity, is not a simple one. But it should be solvable with the modern
computers in most ham shacks. Meanwhile as a ball park figure. You can
expect ordinary Solar system dust and meteors to produce doppler at 40 MHz
of up to 1.4 kHz at the most. But material on an orbit coming from far
away into and through our solar system may in certain circumstances
exhibit doppler shifts well above 3.4 kHz .
So lets hope UNamsat -1 launches soon, and gets its radar operating .
Meanwhile if you monitor 62.495 MHz or there abouts for best European TV
propagation by meteor scatter Eg during the forthcoming April Lyrids
peaking 21st April 93 ( below horizon in our European afternoon ), you
might try rough guesses at the doppler you hear on some rare pings.
Anything over 5 kHz might just be a dust motes of the type Ulysees
encountered, ending its inter stellar travels in a fiery finish as it hits
the Earth's atmosphere. 73 de GM4IHJ @ GB7SAN