Radio Observing Pros and Cons

Observing meteors by radio scatter sidesteps the major obstacles to visual/optical observing:

• Poor weather: clouds, rain
• Bright sky: moon, light pollution, sun.
• Insensitivity to weak events.
  

Principal drawbacks to radio observing:

• The transmitter illuminating the meteor ionization tracks moves along with the Earth but radiants remain fixed in the celestial dome. Maintaining optimum orientation of the receiving system to the radiant is impossible with a single antenna and transmitting source. This is by no means a fatal problem but the observer may need to qualify his findings because of this effect.
  
  
• Along most scatter paths there are liable to be multiple transmitters on the same frequency, contributing to confusing "beat" patterns and possible false event indications depending upon where in the antenna receiving pattern an event occurs.
  
  
• "Morning effect" - the Earth's rotation contributes to the relative incoming velocity of meteors having a vector component tangent to the Earth's orbit, producing an exaggerated in-fall rate and event intensity compared to other times of the day. This can be compensated for by monitoring activity in the absence of meteor showers to determine a baseline for correcting future readings.
  
  
• It is difficult  to sort meteors according to "sporadic" and "shower" classifications. Spatial resolution is mediocre (conversely, temporal resolution is excellent). Sorting according to velocity by measurement of Doppler effect should be possible but has not been demonstrated.
  
  
• Aircraft along the observing path, "sporadic E" and distant thunderstorms may contribute to production of false indications. Improved software pattern recognition techniques could deal with these issues but the work has yet to be done. 
  
   
• Standardization is problematic. When an hourly radio count is published it is seldom, if ever, the case that the observer will comment on how equipment sensitivity is determined or what combination of duration/amplitude is used to decide when an "event" has occurred. With sufficient (but by no means unrealizable) sensitivity and sampling resolution, hourly rates in the hundreds or even thousands can probably be counted even in the absence of a meteor shower. The Scattered Power Index (SPI) being developed for MITROS provides another way of characterizing  event activity which may prove useful in future and which is more amenable to standardization. A first example of the SPI in-use can be found in the 2001 Leonids observing section.

It is our personal experience that counts of radio events lasting 100 milliseconds and longer correlate reasonably well with visually obtained counts but this is by no means a rigorous standard.

Meteor observing by radio scatter is a relatively new science. If there are difficulties then, surely, these are just the kind of interesting challenges that attract enthusiasts in the first place.

To re-iterate, the principal strengths of radio observing are:

• Ability to detect and characterize events well below the visual/optical limits. This is an extremely important advantage, opening new areas of meteor activity to investigation.
  
  
• Insensitivity to adverse visual "seeing" conditions in most circumstances - typical "24/7" availability of observations. That means counting and other analysis of meteor events can proceed when optical methods are rendered useless.
  
  
• Can readily acquire information regarding non-visual aspects of meteor activity. Examples are polarization effects produced by the plasma and properties of wind-shear.