Detecting Meteors on a Cloudy Day
July 2nd, 2008 at 8:50 pm (Astronomy, Technology)
Watching for meteors is a fun pastime on warm summer nights out in the dark desert; you lie back on a blanket and wait for the sky to present its fireworks. The American Meteor Society (AMS) can help you plan your observing times, with this year’s meteor shower calendar and a weekly meteor outlook. But it turns out that you don’t need dark skies, or even night at all. You can observe meteors via radio instead of by sight.
I learned about this technique from an excellent book I am reading titled “The Sky is Your Laboratory: Advanced Astronomy Projects for Amateurs.” The first chapter is devoted to meteor observations, and I was interested to learn that you can record your observations (such as number of meteors observed per hour during a given event) and contribute them to the AMS, which uses this information in the aggregate to characterize meteor activity. Their visual observations webpage is a little out of date (last updated in 2006), unfortunately, but presumably you can still submit your logs.
At any rate, the book then proceeds to describe how you can listen for meteors with your FM radio. Effectively, you use an FM station’s signal as your probe. Signals at the frequencies used by FM stations are high enough that they generally go right through the ionosphere, but if they hit the ionized gas created by a meteor whistling by, they instead bounce back. So you tune your radio to the frequency of a station that is too far away to be received normally (300-600 miles), listen to the static, and wait for a glimpse of non-static. When the signal successfully bounces, you get a snippet of music or speech, and then back to static. You can count these observations just like you’d count meteors streaking across the sky — except that you can count them 24 hours a day, regardless of sky conditions. Awesome!
Rex said,
July 14, 2008 at 2:24 pm
I wonder if you could feed the FM signal into a digitizer–maybe just a sound card!–and look at the Fourier spectrum. You might be able to count events by looking at every time the white noise (is it white?) turns into a 1/f power spectrum. That would defeat the fun of listening to the signal yourself, but if the goal was to collect comprehensive data on meteors, it could do the trick.
Donna said,
July 30, 2008 at 8:42 am
Ok the radio opportunity blows my mind. thanks for this.