Meteor Observation And Radio Detection

Presentation Outline What is a meteor? Characteristics of meteors entering earths atmosphere How can meteors be observed Radio detection methods Free meteor software Share the observations from your station The impact from the end of analog television

What is a meteor A Meteoroid is a grain of sand to boulder sized piece of debris traveling thought our solar system. When a meteoroid enters the earths atmosphere is leaves trail of combusting dust and invisible charged particles and is now called a Meteor If a meteoroid is large enough to withstand incineration in the earths atmosphere to reach the ground it is called a Meteorite Most visible meteors are the size of sand grains Meteor shows are almost exclusively the result of the earth passing through the tail of an ancient comet The word root “meteor” comes from the Greek word meteōros, meaning “high in the air”

What happens in the atmosphere A typical meteor travels through the solar system at 42 kilometers per second The earth moves through the solar system at 30 kilometers per second. These combine to give an upper end for meteor velocity of 72 kilometers per second. 1 k/s = 2237 mph and 72 k/s = 161,000 miles per hour or about 70 times slower than the speed of light Friction from contact with the atmosphere heats the meteor and directly ablates material. The highly energetic material emits light, ionizes itself and the air, emits thermionic electrons The visible portion of a meteor trail represents only a small portion of the energy released, most is invisible as charged particles that can be detected by radio.

How can meteors be observed Direct visual observation using video film loops is a common method of observation. Hundreds of these observatories are located across the county. The IR heat signature of a meteor can also be observed. Sometimes light from the excited atoms can be directly detected The ionization trail is the easiest to detect using radio methods Why: At low frequencies, 1 MHz, only a very small charged particle density is needed to form a near perfect reflector. Radio detection also allows meteor velocity to be inferred from the Doppler shift of the received signal Not surprising the path of ionization is the biggest target and provides the biggest signal – the velocity of high altitude can be measured by the Doppler shift from the tail reflection.

Animation of radio meteor detection

Radio detection of meteors Forward scatter from a remote, over the horizon, transmitter . High power TV and broadcast transmitters are the most practical sources.

Motion changes the received signal Dispersion over dense case

More on the ionization trail Cross section of meteor ionization trail http://www.imo.net/radio/reflection

Time domain signal from a weak ionization trail Under dense case

Time domain signal from a strong ionization trail Over dense case

Software for radio meteors Spectrum analysis software using a SSB radio and the sound card in a PC. Counting method software - a simple electronic circuit reduces the existence or absence of a radio signal to a 1 or 0 applied to the hand shake lines of the RS-232 port. The software then counts events. This method does not detect Doppler shifts in the signal. A variant of the spectrum analysis is the long time chart. The long time chart adds the interesting capability of monitoring aircraft fling over head.

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Meteor Spectragram

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1 year at a glance COLORGRAMME v 2.2 – counting software

Long time charting software MAnalyzer.Exe

NOAA WX Satellites ATP Signal – More fun with radios. Actual image downloaded from NOAA 18 on July 10, 2005 with a ICOM PCR-1000 as hurricane Dennis makes land fall in Pensacola, Florida

End 1J=10^-26 Watt/(M^2Hz)