Potential research projects
The mass of a meteoroid is a fundamential property, but it is surprisingly difficult to measure. Finding the surface area from the deceleration can help, but nearly all meteoroids fragment extensively as they ablate, making the deceleration difficult to connect to individual pieces. The light produced by a meteoroid as it collides with the atmophere is likely proportional to the kinetic energy, but the proportionality constant, the luminous efficiency, is uncertain to at least an order of magnitude. It probably depends on the speed of the meteoroid, the height at which it's ablating, the size of the meteoroid and the flow regime, as well as the meteoroid composition.
The luminous efficiencies of sodium and magnesium, usually strong lines in meteor spectra, have been studied in lab experiments at meteor speeds. By finding meteors whose spectra are consistent with a chondritic composition, we can estimate their total mass from the mass of sodium and magnesium; current studies show that those agree to within a factor of two.
We can then use those chondritic meteors to find the light emitted in lines from oxygen and nitrogen, which should not depend on the composition of the meteoroid but only on other characteristics. We can use the "atmospheric luminous efficiency" to find the total luminous efficiency of non-chondritic meteoroids, and study the dependences with speed, height and other variables.
The composition of meteoroids can tell us something about the composition of their parent asteroids and comets. Meteor spectra give us a better window into composition than dynamics alone, though in faint meteors often only sodium, magnesium and iron lines are visible (other elements in the meteor plasma do not emit strongly in the visible). In some meteors, the spectrum changes with time. Many meteors lose sodium early, with only magnesium and iron visible lower in the trajectory. This suggests that sodium is part of more volatile minerals which lose mass first.
In a few meteors, there is evidence of ablation of olivine, a mineral commonly found in meteorites. Combining the known compositions of potential minerals with detailed fragmentation observations and ablation modelling will give the best constrained meteoroid compositions ever determined.
Meteor shower fluxes are calculated with radar observations of hundreds of shower meteors each day near the peaks of major showers. The radar allows observations during the day and through cloud, making it a valuable tool to study the fainter members of meteoroid streams. The Canadian Meteor Orbit Radar (CMOR) calculates daily fluxes for major meteor showers; many meteor showers do not change significantly on smaller timescales.
There are, however, meteor showers which show structure on hourly timescales, or have brief outbursts lasting much less than one day. The current flux pipeline does not account for all the changes in collecting area over a day, especially at times when the collecting areas are small. There is an opportunity to improve the flux calculations at smaller time intervals by studying the number of shower meteors observed in different parts of the sky under different geometries, which will provide valuable information about rapid changes in meteor showers fluxes.
Meteoroid fragmentation can be observed optically for brighter meteors, but smaller, fainter meteors can't be resolved by cameras. Meteor radars can see much smaller objects, but normally are only counted from one or a few return pulses, with no shape information. If a meteoroid was a single point producing a uniform column of ionization, it would produce a perfect Fresnel pattern (knife-edge diffraction) as it passed through the region visible to the radar; a rapid rise followed by a series of oscillations.
A meteoroid which has fragmented produces many small trails of ionization, each of which produces an overlapping Fresnel pattern in the amplitude and phase of the returned echo. It is possible to perform a Fresnel transform on the echo, which returns both the speed of the meteoroid, and the shape of the ionization-producing region. For echoes with good signal to noise, this should allow a highly spatially resolved snapshot of fragmentation in the km-sized region where scattering is taking place. This will allow population studies of fragmentation among much smaller meteoroids than current optical measurements, and hundreds of thousands of echoes already measured could be used for this purpose.