FM Radio Detection of Meteors

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FM Radio Detection of Meteors


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    Welcome

    My name is Marianne Gualtieri. I'm a 10th-grade student at Villa Walsh Academy in Morristown, New Jersey. During 1998 I observed the Leonid and Geminid meteor showers using the forward scatter of the signal from an FM radio station. My experiment was presented at the Villa Walsh Academy Science Fair. This is a summary of my project which won a trophy at the science fair. Please read our disclaimer .

    Purpose of Experiment

    This experiment was done to compare the peak intensity (meteors-per-hour rate) of the 1998 Leonid meteor shower to the intensity of the 1998 Geminid meteor shower. The 1998 Leonid meteor shower was predicted to have a high peak rate of many hundreds of meteors per hour. The Geminid meteor shower has a typical peak rate of several tens of meteors per hour. This experiment was designed to see if the predictions were true.

    Experiment

    A forward scattering radio observation technique was used so that the meteors could be detected both day and night. Meteors entering the atmosphere will produce a trail of ions that will reflect radio waves. There is only a narrow band of radio frequencies where this will happen. At low frequencies (< 50 MHz) the ionosphere reflects the radio waves without meteors trails. At high frequencies (> 150 MHz), the radio waves are scattered for too short of a time (< 1 second). The FM radio band (88 - 108 MHz) falls within this frequency range. The New York metropolitan area is a difficult place to do this experiment, since there is a strong local FM radio station on almost every frequency. The following graph shows the signal strength at my house for all FM radio frequencies at different directions (bearings). As the legend shows, the darker colors indicate strong local signals, and the lighter colors indicate relatively clear freqencies. As you can see, there are very few clear frequencies in any direction for observing meteor scatter. It should be noted that many of the seemingly clear frequencies at certain bearings are only clear because they're in the Atlantic Ocean.

    FM Spectral Survey

    Legend for FM Spectral Survey

    I chose to monitor CHTZ-FM (St. Catherines, Ontario) on 97.7 MHz for the following reasons.

    The following table and map show all FM radio stations on 97.7 MHz within 600 miles of my house.

    FM Radio Stations on 97.7 MHz within 600 Miles of Ledgewood NJ (N-40:52:41, W-74:39:19)

    Station Power(kW) Distance(mi) Bearing(deg) Location
    WCZX 0.300 67 30 NY Hyde Park
    WVRT 6.000 139 279 PA Jersey Shore
    WCTY 1.900 139 72 CT Norwich
    WAFL 3.000 142 197 DE Milford
    WBKK 1.600 147 9 NY Amsterdam
    WGMM 1.300 152 305 NY Big Flats
    WGMM 0.610 153 304 NY Big Flats
    WINQFM 1.850 184 47 MA Winchendon
    WYAJ 0.004 197 58 MA Sudbury
    WCAV 3.000 203 66 MA Brockton
    WMDMFM 3.300 206 209 MD Lexington Park
    WCAV 2.700 208 65 MA Brockton
    WSGY 3.500 241 255 PA Somerset
    WLERFM 4.600 273 270 PA Butler
    CHTZFM 50.000 282 302 ON St Catharines
    WGMT 0.600 291 29 VT Lyndon
    CHOMFM 41.000 324 9 QU Montreal
    WURB 3.000 355 200 NC Windsor
    WILEFM 1.800 372 260 OH Byesville
    WRONFM 1.000 378 235 WV Ronceverte
    WAKN 50.000 418 53 ME Winter Harbor
    WZBR 3.000 420 201 NC Kinston
    WGGN 0.640 424 274 OH Castalia
    WCJO 3.000 439 252 OH Jackson
    WTGVFM 3.000 453 292 MI Sandusky
    WMJD 2.800 470 237 VA Grundy
    WTGN 6.000 495 269 OH Lima
    WAXZ 2.100 504 253 OH Georgetown
    WCXU 20.000 528 40 ME Caribou
    WOXY 3.000 542 259 OH Oxford
    WMRXFM 2.000 544 291 MI Beaverton
    WMRXFM 4.100 544 291 MI Beaverton
    WWXM 100.000 558 204 SC Georgetown
    WZOW 2.900 587 274 IN Goshen
    CKWMFM 18.000 589 60 NS Kentville
    Data Source - http://207.91.54.150/radiostation/

    97.7 FM radio stations

    A Yagi type directional antenna (Radio Shack 15-2163 High Gain FM-stereo antenna) was used to reduce local interference and increase the intensity of the meteor scatter signal. The antenna was mounted on the roof of our house on a rotor (Radio Shack 15-1225 Antenna Rotor) so that it could be pointed in any direction. The antenna was connected to a sensitive (1.55 mV) FM radio (Yamaha TX-480 FM tuner). This radio was selected because it had a signal strength meter. The voltage from the signal strength meter was connected to an analog-digital converter. A computer recorded the digital signal strength from the analog-digital converter at one second intervals for later analysis. My father has prepared a page with more technical details.

    Data Collection and Analysis

    Both the 1998 Leonid and Geminid meteor showers showed significant activity at their peaks as compared to the background rate of sporadic meteors of 3 - 5 meteors per hour. Since a characteristic of meteor scatter is a rapid rise in signal strength above the background noise, the activity rates were determined by a computer program that counted as meteor signals all peaks with an initial rise greater than 20% of the background in one second. This criterion was selective enough to prevent noise signals from being counted as meteors while still allowing an accurate counting of meteors during very active periods.

    1998 Leonid and Geminid Data

    The following are examples of the raw data for the 1998 Leonid meteor shower. These charts are signal traces of one hour duration beginning at the specified hour. Each horizontal strip is 15 minutes. The first chart shows the signals a few hours before the peak. The second chart shows the signals near the peak. The last chart shows the signals a few hours after the peak. It is easy to see that there are many more signal peaks during the meteor shower than before or after.

    1998 Leonids before peak

    1998 Leonids at peak

    1998 Leonids after peak

    Rates for 1998 Leonids and Geminids

    The following graphs show the meteor count rates per hour that I measured for the 1998 Leonids and Geminids. These rates were determined by a computer program that counted all peaks that climbed at least 20% above the background level in one second.

    Rates for 1998 Leonids

    Rates for 1998 Geminids

    Summary and Conclusions

    The peak intensity of the Leonid meteor shower occurred at 1:00 AM on November 17, 1998. The peak rate was about 80 meteors per hour, significantly less than the predictions. The peak intensity of the Geminid meteor shower occurred at 11:00 PM on December 13, 1998. The peak rate was about 35 meteors per hour, which is the typical rate for the Geminid meteor shower. The Leonids peaked sharply over the course of a few hours, but the Geminid shower peak occurred over a two day period.

    Glossary and Further Information

    Bibliography and Links

    "FM Radio Station Search," http://radiostation.com.

    Gebhardt, Philip, "Observing Meteors on Your FM Dial," Sky and Telescope, December 1997, pp. 108-111.

    Gebhardt, Philip, "Radio Detection of Meteors," http://www.odxa.on.ca/meteor.html.

    International Meteor Organization, http://www.imo.net/.

    Jet Propulsion Laboratory, "Meteor Streams," http://ssd.jpl.nasa.gov/meteor_streams.html.

    "Búsqueda de Meteoros por Radio," Radio Meteor Web Site (in Spanish) by Federico Pfaffendorf, http://radiometeoro.8m.com.

    Radio Meteor Observation, Hiroshi Ogawa, Unviersity of Tsukuba, Japan, http://homepage2.nifty.com/~baron/.

    Struve, Otto, "Meteors," Chapter 14 of Elementary Astronomy (New York: Oxford University Press), 1959.

    Wyatt, Stanley P., Principles of Astronomy (Boston: Allyn & Bacon, Inc.), 1969.

     

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    See my other science fair project Speed of Sound in Gases .


    Comments and technical questions can be addressed to me care of my father, Devlin Gualtieri, at Honeywell Laboratory, Morristown, NJ.


    Copyright © 1999 D. M. Gualtieri, All Rights Reserved.
    Last Update: 12-30-2002