Meteor burst communications
Encyclopedia
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
trails of meteors during atmospheric entry to establish brief communications paths between radio station
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...
s up to 2250 kilometres (1,398.1 mi) apart.
How it works
As the earth moves along its orbital path, billions of particles known as meteors enter the earth's atmosphere every day; a small fraction of which have properties useful for point to point communication. When these meteors begin to burn up, they create a trail of ionized particles in the E layer of the atmosphere that can persist for up to several seconds. The ionization trails can be very dense and thus used to reflect radio waveRadio Wave
Radio Wave may refer to:*Radio frequency*Radio Wave 96.5, a radio station in Blackpool, UK...
s. The frequencies that can be reflected by any particular ion trail are determined by the intensity of the ionization created by the meteor, often a function of the initial size of the particle, and are generally between 30 MHz and 50 MHz.
The distance over which communications can be established is determined by the altitude at which the ionization is created, the location over the surface of the Earth where the meteor is falling, the angle of entry into the atmosphere, and the relative locations of the stations attempting to establish communications. Because these ionization trails only exist for fractions of a second to as long as a few seconds in duration, they create only brief windows of opportunity for communications.
Development
The earliest direct observation of interaction between meteors and radio propagation was reported in 1929 by Hantaro Nagaoka of Japan. In 1931, Greenleaf Pickard noticed that bursts of long distance propagation occurred at times of major meteor showers. At the same time, Bell LabsBell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
researcher A. M. Skellett was studying ways to improve night-time radio propagation, and suggested that the oddities many researchers were seeing were due to meteors. The next year Schafer and Goodall noted that the atmosphere was disturbed during that year's Leonid meteor shower, prompting Skellett to postulate that the mechanism was reflection or scattering from electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s in meteor trails. In 1944, while researching a radar system that was "pointed up" to detect the V-2 missiles falling on London, Hay confirmed that the meteor trails were in fact reflecting radio signals.
In 1946 the U.S. Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
(FCC) found a direct correlation between enhancements in VHF radio signals and individual meteors. Studies conducted in the early 1950s by the National Bureau of Standards and the Stanford Research Institute had limited success at actually using this as a medium.
The first serious effort to utilize this technique was carried out by the Canadian
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
Defence Research Board
Defence Research and Development Canada
Defence Research and Development Canada, also Defence R&D Canada or DRDC , is an agency of the Department of National Defence , whose purpose is to respond to the scientific and technological needs of the Canadian Forces...
in the early 1950s. Their project, "JANET", sent bursts of data pre-recorded on magnetic tape from their radar research station in Prince Albert, Saskatchewan
Prince Albert, Saskatchewan
Prince Albert is the third-largest city in Saskatchewan, Canada. It is situated in the centre of the province on the banks of the North Saskatchewan River. The city is known as the "Gateway to the North" because it is the last major centre along the route to the resources of northern Saskatchewan...
to Toronto
Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...
, a distance of well over 1,000 km. To burst the data, a 90 MHz "carrier" signal was monitored for sudden increases in signal strength, signalling a meteor, which triggered a burst of data. The system was used operationally starting in 1952, and provided useful communications until the radar project was shut down around 1960.
Military use
One of the first major deployments was "COMET" (COmmunication by MEteor Trails), used for long-range communications with NATO's Supreme Headquarters Allied Powers EuropeSupreme Headquarters Allied Powers Europe
Supreme Headquarters Allied Powers Europe is the central command of NATO military forces. It is located at Casteau, north of the Belgian city of Mons...
headquarters. COMET became operational in 1965, with stations located in the Netherlands, France, Italy, West Germany, the United Kingdom, and Norway. COMET maintained an average throughput between 115 and 310 bits per second, depending on the time of year.
Meteor burst communications faded from interest with the increasing use of satellite communications systems starting in the late 1960s. However, in the late 1970s it became clear that the satellites were not as universally useful as originally thought, notably at high latitudes or where signal security was an issue. For these reasons, the U.S. Air Force installed the Alaska Air Command MBC system in the 1970s, although it is not publicly known whether this system is still operational.
A more recent study is the Advanced Meteor Burst Communications System (AMBCS), a testbed set up by SAIC
Science Applications International Corporation
SAIC is a FORTUNE 500 scientific, engineering and technology applications company headquartered in the United States with numerous federal, state, and private sector clients...
under DARPA funding. Using phase-steerable antennas directed at the proper area of the sky for any given time of day, the direction where the Earth is moving "forward", AMBCS was able to greatly improve the data rates, averaging 4 kilobits per second (kbit/s). While satellites may have a nominal throughput about 14 times greater, they're vastly more expensive to operate.
Additional gains in throughput are theoretically possible through the use of real-time steering. The basic concept is to use backscattered signals to pinpoint the exact location of the ion trail and direct the antenna to that spot, or, in some cases, several trails at once. This improves the gain, allowing for much improved data rates. To date, this approach has not been tried experimentally, so far as is known.
Scientific use
The United States Department of AgricultureUnited States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
(USDA) uses meteor scatter extensively in its SNOTEL
SNOTEL
thumb|300px|right|Data from a SNOTEL site in [[Elko County, Nevada]]SNOTEL is an automated system of snowpack and related climate sensors operated by the Natural Resources Conservation Service of the United States Department of Agriculture in the Western United States.There are over 600 SNOTEL ...
system. Over 800 snow water content gauging stations in the Western United States
Western United States
.The Western United States, commonly referred to as the American West or simply "the West," traditionally refers to the region comprising the westernmost states of the United States. Because the U.S. expanded westward after its founding, the meaning of the West has evolved over time...
are equipped with radio transmitters that rely upon meteor scatter communications to send measurements to a data center
Data center
A data center is a facility used to house computer systems and associated components, such as telecommunications and storage systems...
. The snow depth data collected by this system can be viewed on the Internet..
In Alaska, a similar system is used in the Alaskan Meteor Burst Communications System (AMBCS), collecting data for the National Weather Service
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
from automated weather stations, as well as occasional data from other US government agencies.
Amateur radio use
Most meteor scatter communications is conducted between radio stations that are engaged in a precise schedule of transmission and reception periods. Because the presence of a meteor trail at a suitable location between two stations cannot be predicted, stations attempting meteor scatter communications must transmit the same information repeatedly until an acknowledgement of reception from the other station is received. Established protocols are employed to regulate the progress of information flow between stations. While a single meteor may create an ion trail that supports several steps of the communications protocol, often a complete exchange of information requires several meteors and a long period of time to complete.Any form of communications mode can be used for meteor scatter communications. Single sideband audio transmission has been popular among amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operators in North America attempting to establish contact with other stations during meteor shower
Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller...
s without planning a schedule in advance with the other station. The use of Morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
has been more popular in Europe, where amateur radio operators used modified tape recorder
Tape recorder
An audio tape recorder, tape deck, reel-to-reel tape deck, cassette deck or tape machine is an audio storage device that records and plays back sounds, including articulated voices, usually using magnetic tape, either wound on a reel or in a cassette, for storage...
s, and later computer program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
s, to send messages at transmission speeds as high as 800 words per minute. Stations receiving these bursts of information record the signal and play it back at a slower speed to copy the content of the transmission. Since 2000, several digital modes implemented by computer programs have replaced voice and Morse code communications in popularity. The most popular program for amateur radio operations is WSJT
WSJT (Amateur radio software)
WSJT is a computer program used for weak-signal radio communication between amateur radio operators. The program was initially written by Joe Taylor, K1JT, but is now open source and is developed by a small team...
, which was written explicitly for meteor scatter communications.