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Full text of "NASA Technical Reports Server (NTRS) 19880005153: The end height of fireball as a function of their residual kinetic energy"

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N88- 14535 


255 


THE END HEIGHT OF FIREBALL AS A FUNCTION 
OF THEIR RESIDUAL KINETIC ENERGY 

D. 0. ReVelle 

Meteorology Program 
Northern Illinois University 
DeKalb, Illinois, U.S.A. 


Abstract 

Previous analyses of meteoroid compositional groupings have 
utilized the end height of fireballs as a diagnostic tool. From an 
observational perspective this definition is straight forward, but from 
a theoretical viewpoint there are problems with using this operational 
definition. These include: 

a) Dependence of end height on slant range due to extinction for 
long optical paths; 

b) Minimum mass sensitivity effects due to ablation, gross 
fragmentation, etc.; 

c) Limiting wavelength and amplitude detection due to sky 
brightness, response of the emulsion, etc.; 

d) Theoretical predictions of an optically thick radiation field 
at low altitudes for high velocity entry (Biberman et al., 

1980). 

In order to realistically assess the estimated geometric 
uncertainty of + 1km in the observed end height, a theoretical 
definition of the end height of meteoritic fireballs is proposed using 
the results from the integral radiation efficiency model of REVELLE 
(1980). Three photographed and recovered meteorites, Pribram, Lost City 
and Innisfree are used as a calibration for this proposed definition. 
These three fireballs were calculated as having about 99% of their 
pre-atmospheric kinetic energy removed prior to the dark flight phase. 
Assuming that a fixed fraction of the initial kinetic energy will remain 
at the end height, a prediction of the theoretical end height can be 
made directly. 

This definition has been used to evaluate the end height of all 
fireballs that were deduced by WETHERILL and REVELLE (1981) as being 
"meteoritic". In almost all cases the theoretical values are lower than 
the observed values, in some cases being as much as 5km lower. A 
preliminary summary table of results is given below. 

This work was supported by Universities Space Research Association 
while the author was a Visiting Scientist at NASA/MSFC, Huntsville, 
Alabama. 



Evaluation of fireball end heights with 0 = 0.02 /km , H = 8 km and D = 4.60. 


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257 


REFERENCES 

1. L.M. Biberman, C. Ya. Bronin and M.V. Brykin: Motion of a Blunt 

Body Through the Dense Atmosphere Under Conditions of Severe 

Aerodynamic Heating and Ablation, Acta Astronautica , 7, 53-65, 

1980. 

2. D.O. ReVelle: A Predictive Macroscopic Integral Radiation 

Efficiency Model, J. Geophys. Res. , 85, 1803-8, 1980. 

3. G.W. Wetherill and D.O. ReVelle: Which Fireballs are Meteorites?, 

A Study of the Prairie Network Photographic Meteor Data, Icarus , 
48, 308-28, 1981. 

4. D. 0. ReVelle: A Quasi-Simple Ablation Model for Large Meteorite 

Entry: Theory Versus Observations, Journal of Atmospheric and 

Terrestrial Physics , 41 , 453-73, 1979.