(b) (1)(b (3)-P.L. 86-36

Meteor Burst Communications:An Ignored Phenomenon? CU)

'F8P SESBYMIM

(b) (3)-P.L. 86-36

Editor'8 Note: 1bilI paper was a second place winner in the 1990 William Hunt Collection Tecbnica) LiteratureAward.

I. INTRoDUCTION

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

II. THE METEOR

(U) The meteors we will concem ourselves with orbit around the sun in a path thatcoincides with the earth's. These meteors occur at a rate of two to eight billion daily orroughly 50,000 per second. As these meteors catch up with the earth-or are overtaken byit, they enter the atmosphere at a speed of 10 to 75 kilometers per second. The frictioncaused 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

This research report represents the views of the author and does neces88rily reflect the oBicial views of theSigoals CollectionCareer Panel (SCCP)or the NSAJCSS. This document is the property orthe United State8Government and is DOtto be reproduced in whole orin partwithout permisaionofthe Chairman,seep.

47 Tep SECRET I:JMBRA

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1'6' SECRET tlMBRJfc CRYPrOLOGIC QUARTERLY

from the vaporized atoms, causing a trail of positive-charged ions and free electrons toform behind the meteor. This phenomenon occurs at about 115 kilometers altitude and by85 kilometers has completely burned out. The ionized trails last anywhere from a fewseconds to only a few hundredths of a second, and it is these upon which Meteor BurstCommunications (MBC)depend.

(U) There are two ways a meteor. trail redirects the radio wave, depending upon thedensity of the trail. The rust, called an overdense trail, occurs during a meteor shower andhas a free electron density great enough to prevent the radio wave from penetrating. Thewave reflects back to earth much like a beam of light reflects from a mirror. Overdensetrails have a long life, sometimes lasting up to two seconds. These meteor showers,however, play only a small part in MBCoperations because they seldom occur and are onlya small fraction of the total number of meteors that fall upon the earth each day.

(U) The second category of meteor trail, the one best suited for Meteor BurstCommunications, is the underdense trail. This trail, caused by the steady drizzle ofmeteors that fall upon the earth each day, is less dense and allows the radio wave topenetrate. This penetration causes excitement among the electrons, which act as smalldipole antennas, redirecting the wave back to earth in a scattering fashion. These trailslast only a fraction of a second, but because oftheir regularity they are more dependablethan meteor showers.

(U) The total number of usable meteor trails depends on the time of day and month ofyear. Daily, the largest number ofmeteors occurs during the early morning and dissipatesin the evening, around sunset. During the morning the earth is rotating toward the sun,while most meteors move away Crom the sun. This results in the earth sweeping up andovertaking meteors. In the evening the earth rotates away from the sun, and only thosemeteors that overtake earth create usable trails, 'I'hia process is known as the diurnalvariation,' which results in about four times as many meteor trails in the morning as inthe evening.

(U) Nearly three times as many meteors occur in August as in February. Thisseasonal variation occurs because the earth is tilted more toward the sun in August. MBCappear to be most effective from July through September from the hours of 0400 through0800. Table 1 illustrates the variations in the total number of meteors available at varioustimes and dates.

(U) Most meteors are very small, the average meteor being near 1 milligram inweight. The resulting trail is anywhere from 10 to 20 miles long with a radius oCapproximately one meter at the head of the trail;

1. Ronald D. Elliott. "Meteor Bunt. Communications in Tactical Intelligence Support," SIGNAL, November1986, p. 84.

lep SECRET 'IMlRA 48

METEORBURSTCOMMUNlCATIONS

Table 1DallyMeteor Trail AvallabWty

TOP SECR!T tJMBItA

500 r------r---,-----,r-----r-----'-.,...-----.

400

HOURLY 300AVERAGEMETEORRATE

o0001 0400 0800 1200 1600

. LOCALTIME- 24-HOURCLOCK

SEPT 22DEC 21MAR 22JUNE 21

2000 2369

III. PROCEDURE

CURvEsAREHOURI.Y AVERAGERATESFORTHREE·MONTHPERIODS,CENTEREDONTHEDATESINDICATED.

(U) AUMBC systems consist of a master station and one or more remote stations orsensors. Hardware at both the master and remote station usually consists of a small lap-top computer terminal with storage for message bufTering,a transmitter, receiver, andantenna. Frequency usage can range between 20 and 120 MHz. Most systems operate inthe 40 to 50 MHz range, which allows the use of smaller antennas. Transmissions can beeither simplex, half-ciuplexor full-duplex.

49 fe, SEERE' liMBItA

TOP SECREt tlMIM CRYProLOGICQUARTERLY

(U) The master station is responsible for locating a meteor trail that will permit thetwo stations to communicate. To accomplish this, the master station transmits a probethat lI18y consist of a simple, continuous tone on a fixed frequency with the remotestation's receiver tuned to the same frequency. The probe continues to bounce againstvarious meteor trails until a suitable path exists between master station and remote. Theangle of incidence a:nd the angle of reflection determine the path.2 Appendix A illustrateshow a usable trail is determined. When the remote station receives the probe, it replieswith one of its own, and at that time transmission ofdata between the two stations takesplace. When the usable meteor trail bums out, the master station retransmits its probeuntil another suitable path is located.

(U) The period of searching between.usable trails is known as the wait time. Duringthe wait time, the communications are buffered into storage until the next usable meteorappears. .Wait times vary in proportion to the usable time of the trail. Table 2 showsvarious times for usable trails.

Table IWaltTimes Required lorVBriousBurstDurations

BURST DURAnON

.1SECONDS

.2 SECONDS

."SECONDS1.6SECONDS

WAlTTlMEREQUIRED .

17SECONDS36 SECONDS143 SECONDS2DAYS •

• A BURST OF 1.6 SECONDS IS THE RESULT OF AN OVERDENSE METEORTRAIL.

(U) If the system contains more than one remote station, the probe transmitted by themaster may consist of more than just a solid tone. The probe may consist of an addresscode that will trigger the remote station's response. If, by chance, a remote station shouldreceive a probe intended for another remote, it will remain idle until it receives the properaddress.

2. P. S. CannDn aDd A. P. C. Reecl"Tbe Evolution or Meteor Burst Communication Systems: Journtd of tM1Il8titu1ioIJofElectroraiundRadioEngineer••Vol. 57. No.3, MaY/dun. 19B? pp.l01-12.

19PSKRET UMIItA 60

METEORBURSTCOMMUNICATIONS TOP S!C:ItEf tJMIRA

(U) The use of Forward Error Correction (FEC) and Automatic Repeat reQuest (ARQ)equipment is responsible for preventing the transmission of data when no suitable pathexists. If either the master station or any of the remote stations are receiving garbledtraffic, indicating a usable path is burned out, they transmit an ARQ. resulting inretransmission of the data. The FEC equipment is responsible for locating the exactlocation within a message where the path became unusable. This produces relativelyerror-free transmissions.

(U) Data rates for a typical Meteor Burst system range from 75 to 100 words perminute, if unencrypted, to 15 words per minute encrypted. The error rate hovers aroundone error in 50,000 characters. For low-volume users who depend on accurate data, thissystem seems ideal.

IV. ADVANTAGES

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(b) (1)(b) (3)-P.L. 86-36

(U) Another advantage of Meteor Burst Communications is, their independence.Satellites are normaJIy controlled by a third party interested in a profit and are notnecessarily adaptable to the user's needs. This is not the case with MBC; the systembelongs to and is controlled by the user. Since the user owns the system, it is also lesslikely to be compromised.

(U) MBC systems have several advantages over High Frequency (HF) systems. HFsystems usually require multiple frequencies, e.g., day and night frequencies; MBCsystems operate fulltime on one frequency only. MBC equipment is light and durable, andthe manpack is deployable.

(U) Finally, MBC have the ability to survive a nuclear war. Following a nuclearexplosion, the nuclear fallout present in the D-Layer of the atmosphere would thwart HFcommunications. 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 wouldcontinue to bombard the earth's atmosphere, creating trails required byMBC. MBC do notrequire large, fixed ground stations; therefore, they would be difficult to target. A nucleardetonation would, however, require an increase of operating power to penetrate the falloutpresent in the atmosphere's D-Layer. 5

V. DlSADVANTAGES

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

(U) Meteor Burst Communications are also limited by distance. This form ofcommunication is effective only up to a range of 1,200 miles. Any user wishing to transmitfarther than 1,200 miles could not use MBC. It is possible, however, to link several MBCsites together and relay the traffic, which would increase the effective operating distanceindefinitely.

6. Ronald D. Elliott. "Meteor Burst Communications in Tactical Intelligence Support," SIGNAL, November1986, p. 86.

Tap SECRET l:JMBAA 52

METEORBURSTCOMMUNICATIONS TOPSeCReT t:JMBItA

(U) A third disadvantage of Meteor Burst Communications is their incompatibilitywith certain types of signals, mainly voice. Because of the wait time required betweenmeteor trails, voice communications would bebroken into segments. A user might hear 15words, then have to wait 30 seconds for another burst.

VI. EARLY SYSTEMS

(U) The first usable Meteor'Burst Communications system was the JANET, a Canadiansystem developed in 1954. This system was crude by today's standards, but it stimulatedinterest in Meteor Burst. It was a simple system in that neither station used ARQequipment. Communications began when both stations received a 650 Hz tone andconcluded when the signal-to-noise ratio fell below a predetermined level. The averagedata rate for this system was approximately 30 words per minute with an error rate from.1 percent to4 percent.

(U) In 1965, NATO developed the first Meteor Burst system to employ ARQequipment. The system was known as COMET (COmmunications by MEteor Trails) andwas used successfully for point-to-point telecommunications between the Netherlands andFrance. With the advent ofARQ equipment, the error rates fell dramatically.

(U) SNOTEL(SNOw pack TELemetry), developed in the 1970s, is still in use throughoutthe western United States. This system contains 2 master stations and more than 500remote data acquisition sites in 11 western states. The system monitors snowfall andother meteorological data. The 500 unmanned, remote stations are divided into selectivelyaddressed groups of approximately 60 remote stations in each group. Polling a group of 60stations takes an average of 5 minutes.

(U) AMBCS (Alaskan Meteor Burst Communications System) was deployed in the late1970s and is owned jointly by several government agencies. The system collectsaeronautical and environmental data from remote sensors and also serves as a source ofteletype communications between remote manned sites. This system is especially usefulin Alaska because Meteor Burst Communications do not experience the auroralinterference common to High Frequency communications.

VII. WORLDWIDEDEVELOPMENTS INMBC

(U) Although the United States is the leader in MBC technology, it is not alone in theeffort to exploit its usefulness. Several countries, including friendly, hostile, and thirdworld nations, are either developing their own systems or attempting to import them fromtheUnited States. Following is a brief summary ofworldwide developments in MBC.

53 'Fe, SECRET tlM11tA

'f8P 'EERfT tjMIRA CRYPrOLOOICQUARTERLY

,____.1

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7. Ibid.,p.14.

/ ...... // ..8. Ibid., p. 18.

9. Ibid.,p. 22.b) (1)(b) (3)-P.L. 86-36

.1'8' 5EERE'f tlM11tA 54

METEORBURSTCOMMUNICATIONS fap SEEREl' tlMBItA

10. ibid.

11. Ibid., p. 26.

12. Ibid., p. 28.

13. Ibid., p. 29.

United States

--

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-

-

55 T9'SEERET liMBItA

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TOP SI!!Cft£f tJMIRA CRYPTOLOGIC QUARTERLY

VUI. LATESTTECHNOLOGJCAL BREAKTHROUGHS

VHFConvertors

(U) Developed by an American company, IA Research Corporation, theVHF convertorallows the conversion of any VHF radio to an MBC terminal. The time required forconversion is minimal and completely reversible, allowing a terminal to go back and forthfrom VHF to MBC in a matter of minutes..The conversion is possible on any VHF radio,including manpack-deployable units. This development has the potential of opening thefield to thousands ofnew MBCusers. At a recent convention inWashington, D.C., severalthousand dollars' worth of these convertors was stolen in an overnight theft. 15 Theconvertors would be very beneficial to anyone wishing to secretly convert to Meteor BurstCommunications.

Adaptive SignalingRateB

(U) The Meteor Communications Corporation of Seattle, Washington, has developedequipment that allows adaptive signaling rates. The equipment senses the slgnal-te-noiseratio and sets the signal rate accordingly. If a strong signal-to-noise ratio is present, thesignal rate is greater, allowing the transmission of larger volumes ofdata. Manypotentialusers, currently not employing MBC because of MBC's inability to pass large volumes oftraffic, may bevery interested in this development.

IX. CONCLUSIONS

'.... ,..,....... .-------------------------------.,

14. Ibid., p. 24.

15£ Bobby J. Mitchell. "New Meteor Burst Communications Technology Displayed at AFCEA AnnualConvention and Trade Show,"NewMeteorBurstCommunications Technology-InformationMemorandwn, July1987,p.3.

"fe' SECRET

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56

METEORBURSTCOMMUNICATIONS TOP SeER!' UMBRA

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(b) (1)(b) (3)-P.L. 86-36 57 'Fe, StERR l::IMBRA

T9P SECRET l::IMBRA

BIBLIOGRAPHY

Commercial Periodicals

CRYPTOLOGIC QUARTERLY(3) -P.L. 86-361(0)

Boyle, Dan. "Long Distance Communications - Back to Ionization," InternationalDefense Review, May 1988, pp. 127-29.

Cannon, P. S. and A. P. C. Reed. "The Evolution of Meteor Burst CommunicationSystems," Journal of the Institution ofElectronic and Radio Engineers, Vol. 57, No.3,May/June 1987, pp. 101-12.

Day, Willis E. "Meteor-Burst Communications Bounce Signals Between RemoteSites," Electronics, December 1982, pp. 71-75.

Elliott, Ronald D. "Meteor Burst Communications in Tactical Intelligence Support,"SIGNAL, November 1986, pp. 80-88.

Willis, Ken. "Meteor Scatter - European Style," QST, November 1986, pp. 35-39.

f6115EeREf l:JMBRA 58

METEOR BURSTCOMMUNICATIONS

Reports byGovemmentAgencies

Miscellaneous

1'6'SEER!' I:JMIM

(b) (1)(b) (3)-P.L. 86-36

Merritt, Robert H. and Timothy W. Snyder. "Meteor Burst Communications," dateunknown.

A Meteor Scatter Communications System, Hollis International Limited, Hollis, NewHampshire, November 1986.

Various Reports, Files, and Personal Interviews, 1988-1989..

59 lQP SECRETUMBRA

Tap SEERET tlMBItA CRYPl'OLOGICQUARTERLY

AppendillAMeteor BurstComai\UlicatioD& Propagation

TRANSMITTER RECEIVER

The angle formed by the incident ray striking the meteor trail is equal to the angle formed by the ray beingreflected from the meteor trail. This determines the signal path. In the above example, communicationswould occur. Had either station been positioned anywhere else along the line, communications would nothavs occurred. Likewise, the signal would not bave been intercepted unless the interceptor was within thefootprint of the receiveror the groundwave ofthe transmitter.

TOP SEERET tlMBRA 60

b) (1)(b) (3)-P.L. 86-36

METEORBURSTCOMMUNICATIONS

AppendixB

61

'1=0' 5EEAET YM8AA

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'FOP SECRET t:JMBRA

b) (1)(b) (3)-P.L. 86-36

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CRYPTOLOGIC QUARTERLY

Appencllll:C

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FREQUENCY BAND PERCENTAGE USAGE

VHF Low 30-50 MHz 10%VHF High 136-174 MHz 47%UHF Low 380-470 MHz 25%UHF High 470-512 MHz 5%700 MHz 764-806 MH ?800 MHz 806-869 MHz 13%

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UHF Analog

469.1 MHz

Channel 2:

UHF Digital

469.1 MHz

Unity XG-100 Operational Scenario136-870 MHz

VHF Low

30-50 MHz

VHF High

136-174 MHz

UHF Bands

380-520 MHz700/800 Bands

762-870 MHz

Broadband

4940-4990 MHz

Channel 1:

VHF Digital

136.1 MHz

Channel 4:

800 Digital

869.1 MHz

FEDERAL FIREPOLICE EMS

Channel 3:

UHF Analog

469.1 MHz

Channel 2:

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469.1 MHz

Channel 1:

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136.1 MHz

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800 Digital

869.1 MHz

TALK AS ONE – WORK AS ONE

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; Key Characteristics

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