ASSESSMENT OF KINETIC-ENERGY OF METEOROIDS DETECTED BY SATELLITE-BASED LIGHT SENSORS

Radiation energies of bright flashes caused by disintegration of large meteoroids in the atmosphere have been measured using optical sensors on board geostationary satellites. Light curves versus time are avail able for some of the events. We have worked out several numerical tech niques to derive the kinetic energy of the meteoroids that produced th e hashes. Spectral opacities of vapor of various types of meteoroids w ere calculated for a wide range of possible temperatures and densities . Coefficients of conversion of kinetic energy to radiation energy wer e computed for chondritic and iron meteoroids 10 cm to 10 m in size us ing radiation-hydrodynamics numerical simulations. Luminous efficiency increases with body size and initial velocity, Some analytical approx imations are presented for average conversion coefficients for irons a nd H-chondrites. A mean value of this coefficient for large meteoroids (1-10 m in size) is about 5-10%. The theory was tested by analyzing t he light curves of several events in detail. Kinetic energies of impac tors and energy-frequency distribution of 51 bolides, detected during 22 months of systematic observations in 1994-1996, are determined usin g theoretical values of luminous efficiencies and heat-transfer coeffi cients, The number of impacts in the energy range from 0.25 to 4 kt TN T is 25 per year and per total surface of the Earth. The energy-freque ncy distribution is in a rather good agreement with that derived from acoustic observations and the lunar crater record, Acoustic systems ha ve registered one 1 Mt event in 12 years of observation. Optical syste ms have not detected such an event as yet due to a shorter time of obs ervation. The probability of a 1 Mt impact was estimated by extrapolat ion of the observational data. (C) 1997 Academic Press.