Seminar Topics & Project Ideas On Computer Science Electronics Electrical Mechanical Engineering Civil MBA Medicine Nursing Science Physics Mathematics Chemistry ppt pdf doc presentation downloads and Abstract

Meteor Burst Communications


[attachment=24734]

INTRoDUCTION

(U) The idea of bouncing radio signals off meteor trails and back to earth to the
intended receiveris not new. Since the early 1940s various communicators have wrestled
with the possibility. From these early studies, workable systems have evolved until today
it is not uncommon for amateur radio operators (hams) to use this method of
communicating. How is it possible to use a meteor the size of a grain of sand to reflect a
radio signal to its intended receiver? Let us begin with the meteor.

THE METEOR

(U) The meteors we will concem ourselves with orbit around the sun in a path that
coincides with the earth's. These meteors occur at a rate of two to eight billion daily or
roughly 50,000 per second. As these meteors catch up with the earth-or are overtaken by
it, they enter the atmosphere at a speed of 10 to 75 kilometers per second. The friction
caused by the meteor colliding with the atmosphere results in the vaporization of the
. meteor.


PROCEDURE

CURvEsAREHOURI.Y AVERAGERATESFORTHREE·MONTH
PERIODS,CENTEREDONTHEDATESINDICATED.
(U) AUMBC systems consist of a master station and one or more remote stations or
sensors. Hardware at both the master and remote station usually consists of a small laptop
computer terminal with storage for message bufTering,a transmitter, receiver, and
antenna. Frequency usage can range between 20 and 120 MHz. Most systems operate in
the 40 to 50 MHz range, which allows the use of smaller antennas. Transmissions can be



DlSADVANTAGES
(U) The most obvious disadvantage of using Meteor Burst Communications is the very
low data rate. The keying speed of the burst is actually quite fast, 2.0 to 4.8 kilobits per
second, but because of the wait time involved in finding a usable meteor trail, most
systems average only about 100 words per minute of actual data. If a user needs to
transmit large volumes of data, MBC are probably not the right choice. MBC would,
however, make an excellent back-up system for high volume users.
either simplex, half-ciuplexor full-duplex.

METEOR BURST COMMUNICATIONS
[attachment=28550]

INTRODUCTION

Meteor burst communications (MBC), also referred to as meteor scatter communications, is a radio propagation mode that exploits the ionized trails of meteors during atmospheric entry to establish brief communications paths between radio stations up to 2,250 kilometres (1,400 mi) apart.

HOW IT WORKS?

The meteors, we will concern ourselves with, orbit around the sun in a path that coincides with the earth's.
These meteors occur at a rate of two to eight billion daily or roughly 50,000 per second.
As these meteors catch up with the earth-or are overtaken by it, they enter the atmosphere at a speed of 10 to 75 kilometers per second.
The friction caused by the meteor colliding with the atmosphere results in the vaporization of the meteor.
The vaporized trails are further restricted by the atmosphere, stripping electrons from the vaporized atoms, causing a trail of positive-charged ions and free electrons to form behind the meteor.
This phenomenon occurs at about 115 kilometers altitude and by 85 kilometers has completely burned out.
The ionized trails last anywhere from a few
seconds to only a few hundredths of a second, and it is these upon which Meteor Burst Communications (MBC)depend.

METEOR TRAILS

There are two ways a meteor trail redirects the radio wave, depending upon the density of the trail.

OVERDENSE TRAIL

It occurs during a meteor shower and has a free electron density great enough to prevent the radio wave from penetrating.
The wave reflects back to earth much like a beam of light reflects from a mirror.
Overdense trails have a long life, sometimes lasting up to two seconds.
These meteor showers , however, play only a small part in MBC operations because they seldom occur and are only a small fraction of the total number of meteors that fall upon the earth each day

UNDERDENSE TRAIL

It is the one best suited for Meteor Burst
Communications.
This trail, caused by the steady drizzle of meteors that fall upon the earth each day, is less dense and allows the radio wave to penetrate.
This penetration causes excitement among the electrons, which act as small dipole antennas, redirecting the wave back to earth in a scattering fashion.
These trails last only a fraction of a second, but because of their regularity they are more dependable
than meteor showers.

PROCEDURE
All MBC systems consist of :
a master station and
one or more remote stations or sensors.
Hardware at both the master and remote station usually consists of
a small laptop computer terminal with storage for message buffering,
a transmitter,
receiver, and
antenna.

The master station is responsible for locating a meteor trail that will permit the two stations to communicate.
To accomplish this, the master station transmits a probe that may consist of a simple, continuous tone on a fixed frequency with the remote station's receiver tuned to the same frequency.
The probe continues to bounce against various meteor trails until a suitable path exists between master station and remote.
The angle of incidence a:nd the angle of reflection determine the path.