SNOTEL An Alternative to TV Video Carriers

For forward scatter observers the SNOTEL Meteor burst system can be a viable substitute of RF when the Canadian analog TV stations are phased out. Currently this phaseout is scheduled for sometime in 2011. The US stations have already made the jump form analog to digital.

SNOTEL, is an acronym for Snowpack Telemetry.  It began operation in the 1970’s and is run by the Natural Resources Conservation Service (NRCS). For complete description of the system visit the general information page at the home site at:

A quick search of the net will also bring up many hits on this system.

For our purpose we are not interested with the remote slave stations, rather we want to listen for the RF reflected from meteors from the two master stations transmitters. The stations are located near Boise, Idaho and Ogden, Utah and operate on a frequency of 40.530 MHz and run at a power of about 1,500 watts. Two types of encoding are used, a 90 degree FSK for the first ~ 10 seconds of each minute then a 30 degrees FSK for the rest of the minute.

Listen to SNOTEL signal recorded from West Kelowna during intense Es on 2009-06-23 1648 UT. During none sporadic periods expect to hear only brief pings from under dense echoes. Both SNOTEL stations put in strong echoes in southern British Columbia.

More details to come.







2007 12 22 Ursid Outbreak

The 2007 Ursid Multi-Instrument Aircraft Campaign







In late December Jenniskens headed the 2007 MAC Ursid campaign. The shower is produced by ejecta from Comet 8P/Tuttle.

The Ursids shower of 2007 were predicted to peak between 2000 to 22:12 UT which favoured European observers. Radio observation
permitted me to observe the shower despite cloud cover and being on the wrong continent. As a station in NASA’s Global Meteor
Scatter Network, I submitted my initial radio data. The data from my forward scatter station, along those from others, were utilized Ames Research Center for analysis of the 2007 Ursid shower.

The shower was shakedown flight for the 2008 Quadrantid Multi-Instrument Aircraft Campaign, on January 3-4.


Electronic Telegram No. 1188
Central Bureau for Astronomical Telegrams
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)

P. Jenniskens, SETI Institute, reports on elevated Ursid shower rates
between Dec. 22d18h and 23d01h UT, identified as dust ejected from comet
8P/Tuttle prior to 900 AD (cf. CBET 1159).  The outburst was detected in
radio forward-scatter meteor observations by E. Lyytinen (Helsinki, Finland)
during Dec. 22d18h-23d01h and by J. Brower (Vancouver, BC, Canada) during
Dec. 22d18h.5-22d22h.5.  I. Yrjola (Kuusankoski, Finland) reports that 25
Ursid meteors and 16 sporadic meteors were captured on video, with a peak at
around 21h15m, the Ursids being slightly brighter on average than other
meteors that night.
The International Meteor Organization gathered visual observations from
19 observers, who measured a peak ZHR = 34 ± 5 Ursids/hr (vs. predicted
40-70 meteors/hr) at solar longitude 270.53 ± 0.03 deg during Dec.
22d21h12m ± 42m, based on 116 Ursids (assuming a fixed population index
of chi = 2.5).  The predicted peak time was Dec. 22d20h-22d22h.2.

NOTE: These ‘Central Bureau Electronic Telegrams’ are sometimes
superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2007 CBAT

2007 December 31                 (CBET 1188)              Daniel W. E. Green

More to come…

Radio Detection Basics

There are two primary methods being used by amateurs to detect meteors via forward-scatter technique; the FM method and the AM/CW method.

Prior to the 1960’s most of the radio meteor research was conducted at universities,  government and military sites. As it is now,  such institutions were limited by their current funding. This meant meteor observation were often spotty and they were not usually continuous over many days. They utilized radar and back-scatter techniques to detect meteors.

In the 1960’s amateur radio observers listened to a vacant commercial FM radio stations which have their channels in the 88-108 MHz range. As FM radio became more popular it quickly became harder and harder to find a vacant channel to listen for meteors. Even if a vacant was clear locally an observer might be plagued with the local stations’ ‘spilling over’ which  interferes with hearing meteors echoes. Since FM, frequency modulation, there is no easy way to see the Doppler signature of a meteor.

To avoid these limitations, crowding being the biggest problem, observers started using the video carriers of television stations. The video carriers are continuous wave (CW) and narrow band in nature. In North America each of the lower TV channels had one of three possible offsets; minus, zero, and a plus offset. What this means in practice is if channel 3 is an ’empty’ channel locally, then a listener could listen for the video carrier at 61.250 MHz (Zero offset), or on either side of it at 61.260 MHz (+ offset) or at 61.240 MHZ (- offset).  This provided an additional means of reducing possible interference. TV stations are also more spatially isolated than FM stations are so there is again, less chance of interference.

Compared to FM, using a CW signal also gives the observer a means of observing the Doppler signature of each echo by means of FFT (Fast Fourier Transform) routines. This enables studies on Epsilon type echoes, head echoes and other echo phenomenon. Using the Doppler of head echoes the height of a meteor can also be determined by amateurs.

Changes are in the wind

North American radio observers as well as European observers are facing a crisis. The video carrier method is on the verge of disappearing as the two continents switch from analogue TV signals to digital signals. The United States have already made the change and Canada is due in 2011. Many European stations have switched already while others linger on with analogue.

We will discuss alternatives signal sources to TV video carrier  below.


Most people wonder how it is possible to hear a meteor. The answer is when a meteor enters the upper atmosphere it begins pushing atoms aside as it penetrates the ionosphere. These high speed collisions leads to high temperature heating of the meteor. When the energy becomes sufficient the meteor begins to glow at visible light wavelengths. Not  only does the leading front of the meteor glow it also creates a plasma trail behind it. We call this ablation. Mass is being converted into energy and light. The ionized plasma rapidly looses it’s energy and the electrons recombine so most meteors are a brief flash in the sky; the common shooting star we all knew as kids. Most of the visible phase of a meteor ablation occurs between 110 km and 60 km above earth’s surface.

The reason amateurs listen to TV video carriers or FM stations is because the stations provide the source of the RF, radio frequency, power that illuminates (reflects off) the meteor’s plasma trail. Commercial TV stations run 100,000 Watts (100 kW). That is a lot of power! While the stations want their signal to reach their customers’ TV sets in reality much of the signal is radiated out above the horizon and vertically into the sky itself. Usually these signals are lost to the sky as they penetrate the ionosphere without being reflected and continue out into space. If a meteor produces an ionized reflective trail then the VHF (TV and FM) signals can be reflected off the plasma and back down to earth. When the geometry is right radio observers receivers hear a brief “ping”; a musical sounding note of the signal reflecting off the meteor’s trail.

For forward-scatter work the transmitter is located well below the receiving station’s horizon. Usually we strive to have a transmitter between 600 to 1200 km away from the receiving site. See below for the geometry of forward scatter signals.

Diagram from Richardson and Knuteh (1998).

As mentioned, back-scatter is used by the professionals. In this case the receiving station is not below the horizon from the transmitter, rather, it is co-located with the transmitter. The power is borrowed as in forward-scatter it is produced by the transmitter at the site.  The signal is sent from the stations transmitter outwards and the signal is reflected back to the receiver at the same location. Radar is a prime example of back-scatter.

More to follow on video carrier method… For now please see ABMO Radio page to see examples of a working TV video carrier set-up.

Hopefully, one of our members will discuss using the FM method and it will be placed here. If you are interested in the FM I highly recommend going to Ilkka Yrjöllä’s web site.

Even if you’re not interested in FM detection his discussion on forward scatter is the best I’ve seen as is his discussion on CCD, light intensifiers and other meteor subjects.



Software for automatic counting section follows:

  1. Spectrum Lab
  2. mAnalyzer
  3. JAnalyzer
  4. HROftt
  5. Colorgramme Lab V 2.3
  6. Roll your own Colorgramme


2007 09 01 Aurigids Results

The 2007 NASA Aurigid Multi-Instrument Aircraft Campaign (MAC)








As a member of NASA’s Global Meteor Scatter Network I was asked to monitor the 2007 theta Θ-Aurigids shower. Dr. Peter Jenniskens of NASA  was conducting an elaborate airborne observation campaign, the Aurigid MAC.  Some of my radio data results for this campaign can be found on NASA’s Ames Research Center Aurigid MAC web pages.

Why was this shower important?

The shower is produced by the debris field from the passage of  Comet Kiess, C/1911 N1, over 2000 years earlier. The comet is long period comet; it made it’s first passage of the sun around 83 B.C. and competed it’s perihelion approach in 1911. It has been classified as a potential earth impactor. There have been other outbreaks in 1935, 1986, and 1994. Jenniskens and Lyytinen (2003) and Jenniskens and Vaubaillon (2007) predicted a strong outburst in 2007 lasting only an hour and a half. A pdf of the later can be found here.

The comet originated in the Oort cloud some 4.5 billion years ago. Gravity finally perturbed it enough to set it free from the cloud and sent it in bound for an orbit around the sun.

These are the preliminary results of the Aurigids as seen from Kelowna, British Columbia, Canada.

The station for this event consisted of two receivers and two antennas. My primary station listens at 61.260 MHz and uses an ICOM PCR-1000 software driven receiver was used with a 7 element log periodic antenna pointing due south. Counting software: Spectrum Lab FFT and mAnalyzer program.

My secondary station listens a 83.260 MHz an ICOM R-8500 receiver and a no gain, omni directional discone vertical were utilized. Counting software: mAnalyzer with 10 minute splits and Spectrum Lab running in parallel. Transmitters monitored were located in Bilings, Montana, and Bend, Oregon.

Saturation and Under Counts

The primary station began showing a decrease in echo counts starting at 1050 UT and continued depressed counts for about 60 minutes there after. This decline in echo counts was due to saturation, the overlapping of over dense echoes, keeping the software timers and counting routines triggered which led to some under counting the hourly echo counts. The secondary station is much less sensitive and as was hoped for, it did not have this problem during the peak shower.

Primary frequency 61.260 MHz, channel 3 plus offset,  shows the onset of long over dense echoes beginning at 1055 UT and continuing nearly 50 minutes. The recording starts at 0141 UT, blue ticks = 1 minute, red = 1 hour. For display, the spectrogram was set up to show only the brightest echoes, those equal to or stronger than 20 dB . The software  itself recorded all strengths of echoes from 10 dB, 20 dB, 30 dB, and greater than 30 dB  bins as well as the  the duration of each bin.

Brower's Aur outbreak

A very sharp increase in strong, overdense echoes began at 1050 UT. Based on the 10 minute data from both stations, the shower peaked around 1110-1125 UT, September1, 2007.

Results were summarized in CBET 1049:

Electronic Telegram No. 1049
Central Bureau for Astronomical Telegrams
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)

P. Jenniskens, SETI Institute, reports that observations onboard
two research aircraft over Nevada and California indicate that the
anticipated Aurigid outburst (cf. CBET 1045) from the 1-revolution
dust trail of comet C/1911 N1 (Kiess) did occur on Sept. 1 between
10h30m and 12h00m UT, with a peak at 11h15m +/- 5 minutes (the predicted
peak time was 11h33m +/- 20 min).  The peak rate was within a factor of
two of that expected.  Most meteors were in the magnitude range -2 to +3,
as anticipated.
C. Steyaert, Vereniging Voor Sterrenkunde, Belgium, writes that
several stations of the ‘Radio Meteor Observatories On Line’ collaboration
( report high Aurigid activity on
September 1.  A. Smith, Tavistock, U.K., observing at 143.050 MHz, found the
Aurigids to be “very active with big fireballs” between Sept. 1d10h45m
and 1d12h10m UT.  J. Brower, Kelowna, B.C., Canada, observing at 61.26 MHz,
found that “heavy, overdense echoes had a sudden onset starting” during
Sept. 1d10h50m-1d11h00m and continued to be heavy for an hour.  W. Camps,
Tessenderlo, Belgium, observing at 49.990 MHz, observed the following
counts at 10-minute intervals starting:  Sept. 1d10h00m, 6; 1d10h10m, 3;
1d10h20m, 4; 1d10h30m, 2; 1d10h40m, 4; 1d10h50m, 2; 1d11h00m, 7; 1d11h10m,
4; 1d11h20m, 7; 1d11h30m, 7; 1d11h40m, 3; 1d11h50m, 3; 1d12h00m, 4;
1d12h10m, 2; 1d12h20m, 2; 1d12h30m, 1; 1d12h40m, 1; 1d12h50m, 2.
J. M. Trigo-Rodriguez, Institut de Ciencies de l’Espai and Institut
d’Estudis Espacials de Catalunya, Bellaterra (Barcelona), reports that no
signs of Aurigid activity were recorded from Catalonia, Spain, via the
all-sky CCD cameras of the Spanish Meteor Network on Sept. 1d00h30m-
1d04h30m UT.  Meteors of magnitude 3 or brighter were recorded radiating
from the Aurigid radiant, and there were no signs of fireballs from the
dust trail of comet C/1911 N1.

NOTE: These ‘Central Bureau Electronic Telegrams’ are sometimes
superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2007 CBAT
2007 September 3                 (CBET 1049)              Daniel W. E. Green


Graphs Depiction of the outbreak at West Kelowna.

61.260 MHz Primary frequency Echo Count data:


61.260 MHz Primary frequency Echo Duration data:


61.260 MHz Primary frequency Mean Echo Duration data:


83.260 MHz Secondary frequency Echo count data:


83.260 MHz Secondary frequency Duration data:


83.260 MHz Secondary frequency Mean Duration data:


Jenniskens, P., and J. Vaubaillon (2007), An Unusual Meteor Shower on 1 September 2007, Eos Trans. AGU, 88(32), doi:10.1029/2007EO320001.

Lyytinen, E., and Jenniskens (In press 2003), P. Meteor Outburst from Long-Period Comet Dust Trails. Icarus.


VLF and Meteors Links

Please check out these links for a discussion of VLF signatures from meteors:

Beech M, Brown P & Jones J, VLF detection of fireballs, Earth Moon & Planets (Netherlands), 68 (1995) 181.

Beech M, & Foschini, L., Leonid Electrophonic Bursters, Astronomy and Astrophysics 367, (2001), 1056.

Beech M, & Foschini, L., A space charge model for electrophonic bursters, Astronomy and Astrophysics 345 (1999) L27

Rault, Jean-L., On the potential meteors ELF/VLF radiations Perseids 2009 campaign. (2010)



2002 11 19 Leonids Outbreak

Hiroshi Ogawa, head of the International Project for Radio Meteor Observation,  asked radio detection stations from around the world to observe the Leonids during the period of November 1 to November 25, 2002.

Note: Brower was located in Loveland, Colorado at the time of the study and not in West Kelowna.

The following graph shows three stations located in Slovenia, USA, and Japan. The three stations data help trace  the overall activity of the 2002 Leonids.  Notice how as the radian lowered in the sky in Slovenia the radiant was rising for Colorado. Similarly, as the radiant dipped to the west of Colorado it was climbing higher in the sky in Japan, thus giving a continuous view of the overall stream activity over time.

FS Radio results Leo 2002

One of the most rewarding part of the 2002 Leonid study was the recording of a predicted filament  of the comet’s ejecta by Yrjöllä and Brower.

In chapter 14 of Jennniskens book, Meteor Showers and their Parents (Jenniskens 2006:201-215) gives a detail discussion of the filament and why it is important. He states:

Jupiter’s past perturbations may have responsible for the sudden onset of the component in 1994…
I expected the dust component would remain visible post perihelion for at least slightly less than one orbit of Jupiter (<12 yr), thus until 2004 or 2005.

I saw this validated in 2002, when the Filament component was detected for the first time after the perihelion passage of the comet, underlying two very narrow Leonid storm profiles (Fig. 14.41) The observed shift in the peak time and constant width over the years 1994 to 2002 (Table 4) confirms that this component moves about the earth’s path much like individual dust trails in reflection to the ever changing gravitational field of the planets (shaded area in Fig 14.15). Again, more or less following the sun’s reflex motion. (Ibid:214-215)

(Place Fig 14-41 Yrjöllä and Brower here)

More to come…

Jenniskens, P. 2006. Meteor Showers and their Parents, Cambridge University Press, Cambridge, U.K.

2006 01 04 The 2006 Quadrantids

The Quadrantid meteor shower is the first major shower of the new year. More importantly the shower is  a strong and reliable performer. It also happens to be one of the least observed stream of the major showers as early January usually produces low overcasting clouds whether you live in Asia, Europe or North America.

Unlike visual and video observers the low clouds and snow are no problem for radio observers. As the Quadrantid shower echo rates started increasing in West Kelowna, I started watching the live radio page at the RMOB site. I also visited the Japanese sites as well.

By observing these sites I could watch as the echo counts decreased in Europe as the radiant dipped downward, my numbers were on the increase. As mine were peaking the Japanese started seeing the radiant. As my data was taking hits from long duration, overdense echoes I made a note to see if I could make sense of the Quadrantid shower over both geographical space and through time.

I submitted my the results of my analysis to the editor of the WGN, the Journal of the International Meteor Organization. After being reviewed by others it was published. You can download a copy of the paper here.



2006 06 A numerical method to aid

One of the biggest problem with forward scatter data is that each recording station is different from the others. One station might be using a highly directional yagi type antenna with it’s associated forward gain, while others might be using a simple vertical antenna. Others stations use a one wavelength closed loop, discones, or even quadafilar antennas. Each type of antenna places a certain bias on how many echoes are heard per hour.

In addition to the various antennas in use, radio observers also employ many different types of receivers. Some are state of the art while others are less sensitive and less selective than the more capable receivers. This again will influence the station’s daily data.

Yet an other variable among the stations it their frequency and transmitter choice. A few Japanese station listen to beacons on 28 MHz while several Europeans listen to the French satellite radar at 143.  Frequency choice and the transmitter’s output power  can greatly affect  a station’s data.

Recognizing this inter-station variability a few of us decided to attempt a numerical model to ‘level the playing field’ by using the concept of Observability Function. There will be follow ups to improve this initial modeling. It has been field tested and provides some hope on equalizing the data from such diverse stations.

The complete paper (WGN 34:3 p87-97) can be downloaded here.