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As warfighting has progressively become more sophisticated, involving larger forces, encompassing greater areas, and containing many new and more lethal weapon systems, the communication systems supporting the command and control functions have undergone a similar evolution. Communication methods have evolved to the capability of rapidly establishing worldwide “real time” communications through accessing terrestrial and Earth-orbiting communication platforms directly from the battlefield.
However, technological advances in electronic warfare and cyber have enabled adversaries to counter the communication systems by exploiting their vulnerabilities and inherent limitations. For example, satellite communications is vulnerable to jamming and spoofing by adversaries. therefore militaries have been experimenting with many technologies to provide backup in case of the nonavailability of satellite systems. One of the technologies which can provide backup although in a limited sense is meteor burst communications.
Meteor scatter communications rely on the fact that meteors continually enter the Earth’s atmosphere. Meteor scatter propagation uses the fact that vast numbers of meteors enter the Earth’s atmosphere. It is estimated that around 10^12 meteors enter the atmosphere each day and these have a total weight of around 10^6 grams. Fortunately for everyone living below, the vast majority of these meteors are small and are typically only the size of a grain of sand. It is found that the number of meteors entering the atmosphere is inversely proportional to their size. For a tenfold reduction in size, there is a tenfold increase in the number entering the atmosphere over a given period of time. From this it can be seen that very few large ones enter the atmosphere. Although most are burnt up in the upper atmosphere, there are a very few that are sufficiently large to survive entering the atmosphere and reach the earth.
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.
Meteor scatter or meteor burst communications use a form of a radio communications system that is dependent on radio signals being scattered or reflected by meteor trails. The total number of usable meteor trails depends on the time of day and month of year. Daily, the largest number of meteors occurs during the early morning and dissipates in the evening, around sunset. The resulting trail is anywhere from 10 to 20 miles long with a radius of approximately one meter at the head of the trail. 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 scatter communications is a specialized form of propagation that can be successfully used for radio communications over paths that extend up to 1500 or 2000 km.
Meteor Burst Communication System Applications
Meteor scatter or meteor burst communication provides form of radio propagation that can be used when no other form of radio propagation may be available. While data has to be transmitted in bursts and there may be delays, it provides a very useful form of non-real-time communications that can be used in many circumstances.
They are used professionally for a number of data transfer applications, particularly when transferring data from remote unmanned sites to a base using a radio communications link. Nowadays using computer-controlled systems, this form of radio communications can offer an effective alternative to other means, and especially where satellites may need to be used because of the cost. In other applications, radio hams use meteor scatter as a form of long-distance VHF radio signal propagation.
Operational Systems
The United States Department of Agriculture (USDA) uses meteor scatter extensively in its SNOTEL system. The SNOwpack TELemetry (SNOTEL) meteor burst system is an example of effective and efficient use of the spectrum. Over 800 snow water content gauging stations in the Western United States are equipped with radio transmitters that rely upon meteor scatter communications to send measurements to a data center. 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 from automated weather stations, as well as occasional data from other US government agencies.
Polytechnic University presented the advantages of meteor long-distance communication at the China-Russia Symposium
In Nov 2020 Polytechnic University participated in the Second China-Russia Symposium on Polar Acoustics and Information Technology. The event was organized by a SPbPU partner – Harbin Engineering University and the Russian industry center Marinet. The Symposium was supported by the Informatics Department of the Chinese State Natural Sciences Foundation Committee. SPbPU took part in the Second Sino-Russian Symposium on Polar Acoustics and Information Technology
Development of the Arctic region and innovative developments in the field of information technology is now an important area of activity in many countries. Like other universities around the world, SPbPU carries out research work on this issue, including those in collaboration with foreign partners. At the last Symposium, Sergey Makarov, scientific director of the Higher School of Applied Physics and Space Technologies of Peter the Great St. Petersburg Polytechnic University, represented SPbPU and made a report on “Meteorological long-distance communication to ensure the Northern Sea Route in the Arctic in case of emergency.”
“We offer a system of meteor radio communications for areas of the far north. For this purpose, the possibilities of reflection from meteor traces of signals transmitted from ground stations are used. The advantage of this system is that it provides communication in the circumpolar areas, when the work of other types of communication, such as ionospheric short-wave communication or expensive satellite communications is difficult.
The meteorological communication system is used for monitoring – for example, in meteorology or hydrography, for high precision time synchronization, urgent delivery of information to sparsely populated and inaccessible areas. The communication range reaches 2,000 km using power amplifiers up to 1 kW. The equipment has compact appearance and can be located both directly on the ground and on ships,” Sergey Makarov emphasized in his speech.
The topic of the report by scientist Politex aroused great interest from the part of Russian and Chinese colleagues. The partners of SPbPU also spoke about the related directions – for example, Tsinghua University, with which our university has strategic partnership relations, presented the report on the “Technology of underwater communication in the visible light,” and the presentation of Harbin Engineering University was devoted to fundamental research and technical applications of polar acoustics.
Military use
Fo military an MBC system offer a communications medium that provides several advantages over conventional means. The system’s inherent interception, detection, and anti-jamming characteristics, nuclear survivability, simplicity, and low cost make it an attractive
alternative medium to satisfy the ever-increasing requirement for additional communication paths with an over-the-horizon (OTH)
capability.
Due to solar flares predicted, taking down much of the nation’s communications (including com satellites and GPS) and power grids, meteor burst communications (“MBC”) (with integrated Ad Hoc Mesh Networking) is essential to US national security, safety and critical infrastructure.
Following a nuclear explosion, the nuclear fallout present in the D-Layer of the atmosphere would thwart HF communications. It is also likely that satellites and their ground terminals would be high-priority targets. MBC, on the other hand, would fare much better. Meteors would continue to bombard the earth’s atmosphere, creating trails required by MBC. MBC do not require large, fixed ground stations; therefore, they would be difficult to target. A nuclear detonation would, however, require an increase of operating power to penetrate the fallout present in the atmosphere’s D-Layer.
One of the first major deployments was “COMET” (COmmunication by MEteor Trails), used for long-range communications with NATO’s Supreme Headquarters Allied Powers Europe 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. 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 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 simultaneously. This improves the gain, allowing much-improved data rates.
Meteor scatter or meteor burst communications system
Meteor burst systems operate in the frequency range 30-100 MHz. It is generally acknowledged that the optimum band for the normal operation of meteor burst systems is 40-50 MHz. This optimality stems from the ionospheric reflection properties of meteors.
These trails are able to provide a BLOS ionospheric propagation path between ground-based transmitters and receivers. A meteor trail is available to provide a transmission channel between two BLOS locations once every 4 to 20 seconds. The lifetime of the channel is short (1/2 second duration) allowing only enough time for a “burst” of information to be transmitted before the meteor trail decays.
Meteor scatter or meteor burst communications are used for a number of applications on frequencies normally between about 40 and 150 MHz. Although the normal maximum range is around 1500 km, for extended ranges a relay system can be implemented. Here a station approximately half way between the two end points can operate in a store and forward mode, storing the received data and forwarding it on as the trails become available. Time taken for data to be sent across the overall link will obviously increase, but for most systems that would consider meteor burst communications, this should not be a problem.
Meteor Burst communication system technology
In view of the fact that the ionisation trails left by the meteors are small, only minute amounts of the signal are reflected and this means that high powers coupled with sensitive receivers are often necessary. To provide a communication channel between two stations, the meteor trail must be spatially located in the common volume of the antenna patterns of two stations. The antennas used with meteor burst systems usually have half-power beamwidths of about 30 degrees.
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. 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 either simplex, half-duplex or full-duplex.
The trails of ionisation left by meteors are short lived, and therefore the communications used needs to be able to be able to detect when a path exists and send high speed data while the radio path exists between the transmitter and the receiver. A typical meteor scatter communications system, or meteor burst communications system will operate in a number of stages.
A transmitter or master station will send out a probe signal. This is typically coded to ensure that communications are secure and not corrupted. A meteor trail will appear at some point that enables the transmitted probe signal to be reflected back so that it is received by the remote station. When this occurs the remote station will decode the signal and it will in turn transmit back a coded signal to the master. This signal is in turn checked by the master. Once the link has been verified, data can be exchanged in either or both directions. Data is transmitted at high speed and also with constant error checks as the link will only be able to support communications for a few tenths of a second. After this point the diffusion of the meteor trail will reduce the ion density to a point where it will not reflect the signal back and the link will be lost.
When the link is lost, the master station starts to transmit its coded probe signal searching for the next meteor trail that will be able to support communications. The period of searching between usable trails is known as the wait time. During the wait time, the communications are buffered into storage until the next usable meteor appears. ·Wait times vary in proportion to the usable time of the trail. If the system contains more than one remote station. the probe transmitted by the master may consist of more than just a solid tone. The probe may consist of an address· code that will trigger the remote station’s response. If. by chance, a remote station should receive a probe intended for another remote, it will remain idle until it receives the proper address.
The use of Forward Error Correction (FEC) and Automatic Repeat reQuest (ARQ) equipment is responsible for preventing the transmission of data when no suitable path exists. If either the master station or any of the remote stations are receiving garbled traffic, indicating a usable path is burned out, they transmit an ARQ, resulting in retransmission of the data. The FEC equipment is responsible for locating the exact
location within a message where the path became unusable. This produces relatively error-free transmissions.
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. Data rates for a typical Meteor Burst system range from 75 to 100 words per minute, if unencrypted, to 15 words per minute encrypted. The error rate hovers around one error in 50,000 characters. 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.
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