Sam's Meteor Radio Echo Page

Background information
What Frequency is Best?
NAVSPASUR
216 MHz Pre-amp
Antenna Considerations for NAVSPASUR
Low VHF TV Stations
Shortwave Broadcast Stations
Receiving Equipment
Lightning Echoes
Ham Radio Meteorscatter
Meteor Links
Astronomy
Ham Radio
Shortwave Listening
Radio Scanning
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This page is intended to help anyone who might be interested in setting up a receiving system to monitor meteor radio echoes. Some of the text below was taken from e-mail discussion.

Background Information

Here's where the story begins. Just prior to the recent Perseid Meteor Shower, I re-visited a web site that provides streaming audio of meteor radio echoes. I had planned to purchase a portable shortwave receiver to take on business trips. So, I decided to purchase one that could be used for both business trips and for listening to meteor radio echoes. I've made numerous two way radio contacts via meteor scatter using Amateur Radio since the late 1980s. Other ham radio operators and amateur astronomers monitor meteor activity using dedicated receivers. These ham radio operators monitor meteor radio echoes to determine when meteor activity should support communications. Some amateur astronomers monitor "radio meteors" to measure the intensity of various meteor showers. With fairly sophisticated equipment, astronomers can determine orbital parameters for meteor showers, and the shape and density of the dust cloud that produces the meteor shower.

Many, if not most, meteor showers have been directly associated with periodic comets. When a dust trail and meteor shower are associated with a comet, data from monitoring meteor radio echoes can give scientists insight into the history of the comet. I find listening to meteor radio echoes to be very interesting. You can also listen to radio echoes from aircraft, satellites, and in some cases, lightning. A meteor radio echo receiving setup might be useful for monitoring auroral activity too, depending on the frequency, and the location of the source transmitter in relation to the intensity and location of the aurora.If you want to listen to a sample of meteor echoes, you're in luck. NASA has an on-line receiver that you can listen to via the internet. Here's the URL:

NASA Meteor Receiver

Stan Nelson's Meteor Receivers

Here's a WAV recording of several meteor echoes made using a receiver monitoring a low VHF TV channel:

http://spacescience.com/audio/leonidsample.wav

Yahoo search results on "Meteor Burst Communications"

Yahoo search results on "Meteor Scatter Communications"

An excellent explanation of how meteor radio echoes are produced is available on the International Meteor Organization webpage.

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Which Frequency is Best?

A commercial communications industry has been built around meteor scatter communications. The most common region of the radio spectrum for commercial two-way meteor scatter operation is from 30 to 50 MHz. This region of the radio spectrum offers the best of many factors related to meteor scatter communications. The frequency is low enough that the ionized trails from meteors efficiently reflect (actually the ionized trails refract radio waves, but that's another story) signals, antenna sizes are manageable, good stable receivers and transmitters are readily available, F layer ionospheric propagation is relatively rare, D layer ionospheric absorption is low, and this frequency range is not widely used for terrestrial point to point communications, most of which have moved to high VHF and UHF frequencies. More information on the history and utilization of meteor burst communication is at:

History of Meteor Burst Communications

Less ionization is required within the low VHF frequency range than at higher radio frequencies for effective propagation, so lower power levels can be used. That is why the NASA meteor receiver mentioned above monitors TV channel 4 signals on 67.25 MHz. Even though the transmit signal is beamed at the horizon, TV transmitters typically use high power levels and more of the signal is reflected by the meteor induced ionization at the frequencies used by low VHF TV channels (channel 2 through 6) than would be the case at higher radio frequencies.

Meteor scatter operation is less dependable as the frequency increases. Above 100 MHz, more power and higher gain antennas are required. Even with more power and higher gain, fewer meteor radio echoes will be detected.

At HF frequencies, interference from man-made and natural sources can be problematic, especially if automated means of counting meteor radio echoes are employed. F-layer propagation, and longer groundwave propagation also introduces problems.

Therefore, the lower portion of the VHF frequency range is the optimum part of the RF spectrum for monitoring meteor radio echoes.

A good primer on meteor scatter operation is at:

http://www.imo.net/radio/

Additional information on meteor scatter operation is available through the following URLs:

  1. http://radio.meteor.free.fr/
  2. http://www.qsl.net/dk3xt/ms.htm
  3. http://www.vhfdx.de/meteorscatter.html
  4. http://www.vhfdx.de/wsjt/
  5. http://www.kolumbus.fi/oh5iy/
  6. http://www.qsl.net/w8wn/hscw/hscw.html
  7. http://www.veron.nl/amrad/mslinks.htm
  8. http://6mt.com/wsm.htm
  9. http://members.cox.net/fmdxweb/thomas.html
  10. http://pulsar.princeton.edu/~joe/K1JT/WSJT_QST_Dec2001.pdf
  11. Google Search for Meteor Scatter

An exception to the frequency rule is the NAVSPASUR radar system.

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NAVSPASUR - The Navy's Space Surveillance Radar System (i.e., "The Fence"} Responsibility was transferred to the USAF in 2004.

I use the Navy's space radar system because it is located nearby, and it transmits at a very high power level, is on the air 24X7X365, and the radar signal is beamed into space. It's an ideal signal source, and in addition to meteor radio echoes, its signal can also be used to detect echoes from aircraft, satellites, and lightning!

Normally, frequencies above 150 MHz are not used much for monitoring meteor radio echoes, but since the NAVSPASUR radar runs very high power, many meteors produce enough ionization to allow echoes to be heard using evan a modest receiving setup.

The NAVSPASUR "Fence" has three transmitters:

See: http://www.fas.org/spp/military/program/track/spasur_at.htm

See: Yahoo Search Results on NAVSPASUR and http://www.fas.org/spp/military/program/track/spasur_at.htm

The radar's radiation pattern is in shape of an Oriental hand fan, that is aligned east / west. The exact details of the pattern are not available. However, ionized paths produced by meteors will refract the radar's signal. Ionization produced by lightning can also reflect the signal.

To receive lightning echoes, you will likely need to be within approximately 250 miles of the thunderstorm, which is in turn, within line of site (preferably along an east / west line) of the transmitter at Lake Kickapoo. To receive meteor echoes, your receiving setup can be more than 500 miles from the transmitter. The farther your receiver is located from the transmitter, the more receiver and antenna gain that will be required due to signal attenuation resulting from path loss effects.

Echoes from meteors can be easily heard, as can echoes from aircraft and satellites passing overhead in space. Occasional relatively strong "anomalous" echoes with doppler shift rates between that of satellites and aircraft are heard. I'm not certain what the source of these might be.

This high power radar system even produces echoes from the Moon!

Moon Bounce using NAVSPASUR - And a second article

Additional information is available through the following URLs:

Article on Tracking Satellites using NAVSPASUR - Second article - Third Article

Tom Kneisel's presentation - Tracking Satellites on a Shoestring Budget

The more distant your receiver is from the NAVSPASUR transmitters, the more antenna gain (longer boom with more elements) and system (pre-amp) gain you will need.

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Antenna Considerations for NAVSPASUR

To receive meteor echoes using the NAVSPASUR transmitter, your receiving setup must be within line of site distance of an area 60 miles above sea level (where meteors burn-up in the atmosphere) that is illuminated by the NAVSPASUR signal. The farther your receiver is located from the transmitter and the meteor's path, the more receiver and antenna gain will be required due to signal attenuation resulting from path loss effects.

The antenna selected depends much on the frequency that you decide to use. For use with the NAVSPASUR radar, I chose a horizontally polarized 7 element M2 220 MHz yagi. (Horizontal polarization was selected to attenuate nearby vertically polarized business band signals. Antenna polarization is not critical for meteor radio echoes, since the signals reflected by meteor trails are randomly polarized.)

The gain provided by the 7 element yagi allows reception of relatively small meteors that produce weak echoes, and better reception of echoes produced by satellites. The downside to a high gain directional antenna is that it is directional and it requires more space than a lower gain antenna.

Since I was primarily interested in receiving echoes from meteors, my antenna was pointed toward Lake Kickapoo, Texas at an elevation angle of approximately 45 degrees, to direct the antenna beam toward an area 60 miles above a point half way between Lake Kickapoo, Texas and my location. (Sixty miles above sea level is where most meteors meet their end in a fiery stream of ionized gas and dust.) To determine the optimum elevation angle for a directional antenna, you must know the distance between your location and the transmitter's location. To simplify matters, we will make a few assumptions:

  1. Meteors burn-up and produce an ionized trail at an altitude of about 60 miles above sea level
  2. The curvature of the Earth will not be considered
  3. The antenna elevation formula applies regardless of the frequency used

Here's the formula:

Antenna elevation angle = arc tan (60 mile altitude / 60 mile distance to the halfway point)

Antenna elevation angle = arc tan 60/60 = arc tan 1 = 45 degree elevation angle

The vertical and horizontal beam widths of the M2 six element yagi are both about 50 degrees, which is broad enough that the slight error introduced by not considering the curvature of the Earth should not significantly effect reception. Use a map to determine the direction to the transmitter. Then, use a compass to aim your antenna accurately. You should take into account the magnetic deviation (i.e., the difference between true north and magnetic north for your location), although the yagi's 50 degree horizontal beamwidth is wide enough to compensate for any error introduced by magnetic deviation.

Antenna Elevation Angle versus Distance between Transmitter and Receiver in Miles
Distance in Miles between TX & RX 1/2 Distance Antenna Elevation Angle in Degrees
60
30
63
90
45
53
120
60
45
150
75
39
180
90
34
210
105
30
240
120
27
270
135
24
300
150
22
330
165
20
360
180
19
390
195
17
420
210
16
450
225
15
480
240

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Additional information on antennas, and antenna theory can be found in the ARRL Antenna Handbook. See:

http://www.arrl.org/catalog/?item=9043#top

If the above link doesn't work, then go to the following link and search on "Antenna Handbook".

http://www.arrl.org/catalog/

The ARRL VHF handbook contains additional information on designing VHF receiving systems.

`For the space radar at Lake Kickapoo, I use a commercially manufactured six element 220 MHz yagi-uda antenna. This antenna is available from Texas Towers in Plano, Texas. See:

http://www.texastowers.com/m2_2227ez.htm

The 220 MHz M2 antenna uses a type-N connector and the receiver uses a BNC. Adapters are used at both ends to accept the UHF type connectors that are used on the coaxial cable.

If you put your antenna in the attic, you won't have to be concerned about a direct lightning strike. However, a nearby strike outside could still induce current into your antenna and feedline, resulting in damage to your receiver. Note that any metal used in the construction of your roof, such as metal flashing or aluminum lined insulation may attenuate signals arriving at your antenna, and require that you mount your antenna outside.

Note that any metal used in the construction of your roof, such as metal flashing or aluminum lined insulation may attenuate signals before they arrive at your attic mounted antenna, and may require that you mount your antenna outside.

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216 MHz RF Pre-Amp for use with NAVSPASUR

An RF pre-amp will increase the strength of received signals and compensate for signal attenuation resulting from losses in the coaxial cable. Here's the description of the pre-amp:

219LNAWP - 219 MHz GaAs FET pre-amp., 18dBG, <0.7DBNF, RX only! WP enclosure Type "N" connector

Here's the Downeast Microwave webpage URL:

http://www.downeastmicrowave.com/

Search for "219LNAWP".

If you ask, Down East Microwave will peak the pre-amp's performance to 216.98 MHz.

If you don't live close enough to one of the NAVSPASUR transmitters, then selecting an unused TV channel between channels 2 to 6 may be your best choice. The lower frequency TV channels should also yield more meteor radio echoes than the NAVSPASUR radar.

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Using Low VHF TV Stations

Low VHF TV stations are effective signal sources for monitoring meteor radio echoes.

Two low VHF TV channels are available for monitoring in the Dallas area. Channels 3 and 6 are unoccupied in the immediate Dallas/Fort Worth area, so I checked both. A TV station is on channel 3 in Shreveport and on channel 6 just south of Waco. Signals from these two stations should "illuminate" any meteors that burn-up over my location.

Channel 3 should produce better results, because of its lower frequency and because it is more distant than the channel 6 transmitter. (Remember, less ionization is required to reflect lower frequency signals.)

Due to the relatively high power levels used, TV station video carrier frequencies are normally monitored. For USB, the receiver is tuned to 1 kHz below the listed frequency and for LSB, the receiver is set 1 kHz above the video carrier frequency.

Low VHF video carrier frequencies in MegaHertz for the USA.

TV Channel
Video Carrier - (A)
Video Carrier 0 (B)
Video Carrier + (C)
2
55.240
55.250
55.260
3
61.240
61.250
61.260
4
67.240
67.250
67.260
5
77.240
77.250
77.260
6
83.240
83.250
83.260

Set your receiver to LSB, determine which channel to use and then tune 1 kHz above the video carrier frequency (e.g., 61.2510 MHz for channel 3, video carrier 0).

TV Antennas

A standard TV antenna from Radio Shack, especially those designed for fringe area reception, pointed at the zenith (straight up) should work just fine for this application. You can even ground mount it, with the reflector resting on the ground and the antenna pointed straight up. Since signal attenuation due to foliage is not an issue at these frequencies, you could mount the antenna on the ground under a tree or even in your attic.

If you don't want to purchase an antenna, a simple home made wire dipole will work well, but a two element wire yagi will work even better. .Adding a reflector to your 1/2 wavelength dipole.will improve performance by increasing gain and attenuating ground wave. (TV stations within 200 miles or so, can produce enough ground wave to be heard with this setup.)

The formula for determining the length of the driven element is:

468 divided by the frequency in MegaHertz (MHz) equals 1/2 wavelength in feet

Cut the driven element in half. Install a center insulator, and then connect your coaxial cable to the antenna at the center. Stretch the driven element out in a straight horizontal line. Make the reflector 5% longer than the driven element. The reflector does not need to be cut in the center and remains a full 1/2 wavelength in length. Stretch the reflector in a straight horizontal line across the floor of your attic. Position the driven element about 1/4 wavelength above and parallel to the reflector.

Dipole construction information is here:

http://www.arrl.org/tis/info/pdf/9106023.pdf

I stapled the wires to wooden supports inside my attic and used RG-213 coaxial cable to the receiver. However, a short run of RG-58 will work, but the larger RG-213 cable produces less signal loss than the smaller RG-58. If the distance from your receiver to the antenna is more than 50 feet, then consider using RG-213. RG-8X is another good choice for longer distances. If the distance from your receiver to your antenna exceeds 100 feet, then you should consider installing a pre-amplifier near the antenna feedpoint. The preamplifier overcomes the feedline loss by amplifying the signal from the antenna.

Don't believe that inserting a pre-amp near the receiver will be as effective. The preamplifier must be mounted close to the antenna feedpoint so that it is amplifying the signal from the antenna before the signal is attenuated by losses in the coaxial cable. It is best to purchase a pre-amp that includes a gain adjustment and a switch to attenuate FM radio signals. Too much gain may result in receiver overload and intermodulation distortion due to strong local transmitters, such as nearby TV or FM stations.

Radio Shack offers pre-amps for TV frequencies.

A second source for preamplifiers is Grove Enterprises.

Another easy to construct wire antenna is a one wavelength loop. When mounted in a horizontal plane, the one wavelength loop antenna will provide greater attenuation of ground wave signals than a dipole or the two element wire yagi array.

Use the following formula to determine the length:

1005 divided by the frequency in MHz equals the length in feet of a one wavelength loop antenna

The shape of the loop is relatively unimportant. It can be either square, an equilateral triangle, or circular. Rectangular shapes should be avoided because performance may be impaired and antenna gain reduced. Mount the loop in a horizontal plane.

Cut the loop at a convenient spot, install a center insulator, and then connect the coaxial cable's center conductor to one side and the shield to the other. Install your pre-amp close to the antenna. The feed point, that is the point where you connect the coaxial cable to the loop, is not critical.

As with the wire yagi, you can improve performance by adding a reflector. Make the reflector 5% longer than the driven element and mount it about 1/4 wave under the driven element.

General construction techniques for a cubical quad loop antenna are at:

http://www.geocities.com/cq43ax101/Cubical_Quad.html

The article provides information on how to connect the coax to the loop antenna.

Most commercially available TV pre-amps use Type "F" RF connectors. Use of a TV antenna balun (balanced to unbalanced transformer), provides a convenient way to connect a coaxial cable that uses a Type F connector to your antenna. Type F connectors and ready-made coaxial cable with Type F connectors are available at Radio Shack.

A UG-238 VHF coax connector can be used at the feedpoint for either the wire yagi or the loop. A mating PL-259 connector is soldered to the coaxial cable. The addition of a center insulator at the feedpoint will keep the two sides of the antenna separated and help prevent shorts. BNC connectors can also be used. (The IC-PCR1000 receiver uses a BNC connector. )

FM broadcast stations can also be used as signal sources.

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Using Shortwave Broadcast Stations as Signal Sources

Shortwave broadcast stations can be used too! A Portuguese meteor receiving station monitors a shortwave station near 21.6 MHz which is located over the horizon from the receiving location, far enough away to attenuate ground wave, but close enough that no skywave or "skip" can be heard. Meteors that enter the Earth's atmosphere between the transmitter and the receiving station reflect the station's signal to his receiving setup. Due to the lower transmit frequency, the doppler shift is typically within +/- 25 Hz of the carrier frequency. The 21.6 MHz HF frequency yields even more meteor echoes than the low VHF TV station frequency, since the ionized meteor trail reflects more of the signal than at HF frequencies than at the higher VHF frequencies.

The downside is that on HF, static from lightning and other natural and man-made noises may make receiving meteor echoes more difficult. And, if you are using a computer program to count meteor echoes, sferics and noise may make your counts artificially high.

Here is a link to an excellent presentation on YouTube by DK8OK on using a shortwave receiver to detect meteors and jets.

http://www.youtube.com/watch?v=xgrxQdRrCRE

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Receiving Equipment

I selected the PC controlled ICOM IC-PCR1000 receiver, because of its wide frequency coverage, performance, features, and relatively low cost. The downside to this receiver is that you must have a PC with an RS232 serial port to control it. Many newer PCs only offer USB ports, but you can purchase a USB to RS232 serial adapter. Or you can go to flea markets and purchase an older PC or laptop.

ICOM now offers two new small receivers, both of which can operate with or without a PC connected. See:

http://www.icomamerica.com/receivers/pc.asp

A more expensive alternative is the ICOM IC-R8500 table top receiver.

Click here for more information on the IC-R8500

Whichever receiver you choose, it must be stable and be capable of receiving CW or SSB signals.

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Lightning Echoes.

Ionization produced by lightning can also reflect radio waves. My setup easily detects lightning radio echoes, with the best results occurring when large storms are located near the halfway point between my receiver and the Lake Kickapoo transmitter. However, the ionized paths produced by lightning should scatter the NAVSPSUR radar signal in all directions. Receiving setups similar to mine that are located as far away as Norman, Oklahoma or Austin, Texas should be able to detect lightning radio echoes, assuming that the target storm is being illuminated by the NAVSPASUR radar signal AND your antenna has line of site visibility to the target thunderstorm and lightning path.

Lightning radio echoes produce a sound that differs from those produced by meteors. Lightning echoes tend to warble and have a duration from a few hundred milliseconds to about one second. It is rare for lightning echoes to last much longer than one second. Lightning produced radio echoes are not the crackling static typically heard on HF frequencies. I suspect the odd sound produced by lightning radio echoes is the result of amplitude variations and slight frequency changes caused by the zigzag path taken by lightning. Remember that doppler shift results from changes in the velocity of the signal source, or reflector, as referenced to that of your receiving setup. As lightning propagates, it does so in steps and bursts. This stepped movement of lightning likely accounts for the amplitude changes and slight frequency shift of the echoes.

Here is a sample audio recording using my setup, which consists of an IC-PCR1000 receiver, a M2 six element horizontally polarized yagi, and a Downeast Microwave pre-amp, monitoring the Lake Kickapoo radar. The storms producing the echoes were located about halfway between my location and Lake Kickapoo.

http://www.k5kj.net/Audio_Files/LIghtning_20061229.mp3

If you install the antenna in your home's attic, you won't have to be concerned about a direct lightning strike. However, a nearby strike outside could still induce current into your antenna and feedline, possibly resulting in damage to your receiver.

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More on Actual Meteor Radio Echo Results

With my receiver tuned to 61.2510 MHz, which corresponds to the TV channel 3 video carrier frequency, AND using the receiver's DSP notch filter, the small amount of annoying ground wave from the Shreveport channel 3 transmitter is eliminated. (The DSP noise filter is also activated, which reduces receiver hiss). Meteor pings and longer duration echoes are not affected. Actually, many more pings can be heard with the notch filter in use than without! However, when the direct signal from Shreveport is weak, I turn off the DSP. The antenna is a two element wire yagi, pointed straight up at the zenith. Ground wave from Shreveport was attenuated, but it's still audible.

The standard formula was used to determine the length of the 1/2 wave driven element - 468 / frequency in MHz = length in feet. The driven element was cut at the center where a coaxial feedpoint using a UG-238 coaxial cable connector was inserted (and soldered). The reflector was cut 5% longer than the driven element and was spaced 1/4 wave below the driven element. The 1/4 wave spacing should yield a nice fat cardioid shaped antenna pattern pointed straight up.

This setup easily detects meteor radio echoes, even without a pre-amp. Here is a sample recording of meteor radio echoes from my receiving setup tuned to 61.239 MHz, TV video channel 3a. (Left audio channel is the meteor receiver. The right audio channel is a simultaneous recording of WWV.)

http://www.k5kj.net/Audio_Files/Meteor_20061119_sample.mp3

The number of meteor radio echoes heard varies on a diurnal and annual basis. See:

http://www.atmos-chem-phys.net/4/1355/2004/acp-4-1355-2004.pdf

Special software is available to monitor and record activity. R_Meteor software is widely used for monitoring meteor echoes and is available for download at the following URL:

http://www.coaa.co.uk/r_meteor.htm

Software intended for use with PSK31 (PSK31 is a digital radio teletype mode) incorporates a nice waterfall spectrum display that does a great job for shorter duration echoes. It's called DigiPan. You can download a copy here:

http://www.digipan.net/

Some observers use software to report their observations in near real-time. See:

http://radio.data.free.fr/main.php3

RMOB software is available here:

http://visualrmob.free.fr/download.php?lng=en

Additional information is available here:

http://radio.meteor.free.fr/us/main.html

and here:

http://www.roswellastronomyclub.com/meteors.htm

and links to live meteor radio echo receivers:

http://www.roswellastronomyclub.com/radio_meteors.htm

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Meteor Links

  1. Meteor Showers On-Line (Gary Kronk)
  2. Current Comets (Gary Kronk)
  3. Meteor Showers and their Observation & Site 2
  4. Meteors, Meteorites and Impacts
  5. International Meteor Organization
  6. The North American Meteor Network
  7. Listen to Meteors Live!
  8. Stan Nelson's page
  9. Explanation of Meteor Radio Echoes
  10. How to bounce radio waves off of meteor trails!
  11. Meteor Detection by Radio from the Roswell Astronomy Club
  12. USA Television Frequency Allocations for selecting an unused frequency to monitor in your area (suggest that you use the video carrier frequency and adjust your receiver offset for a 1 kHz tone).
  13. Spectrum analysis of meteor radio echoes using your computer's sound card
  14. Recording meteor radio echoes using your computer's sound card using R_Meteor
  15. DigiPan - A waterfall type audio spectrum display intended for PSK31 reception, but it works great for meteor pings too!
  16. The Global Meteor Scatter Network
  17. BEACONet
  18. Graphical plot of today's meteor activity
  19. The RAMSES Project
  20. Radio Meteor Observations
  21. More info on Radio
  22. The Meteorite Photo Gallery
  23. MeteorLab.com
  24. Stardate
  25. International Meteor Organization
  26. IMO How to Photograph Meteors
  27. Observation Groups
  28. Meteor WWW Links
  29. Leonids
  30. Leonid Links
  31. German Meteor Observers
  32. Society of Spanish Meteor Observers
  33. Meteor and Comet related web sites Links from Spain
  34. Meteorites.com
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Copyright 2007 - Samuel D. Barricklow - All Rights Reserved


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Last revised: June 5, 2010