Space Exploration Vision- The Science Challenges
- Paper number
IAC-04-Q.6.02
- Author
Mr. Roger K. Crouch, Space and Technology Insights, United States
- Year
2004
- Abstract
The development of methods for evaluating meteors and fireballs parameters from observational data requires much attention since the available literature, including handbooks (see, e.g., [1]), contains discrepancies that are of a basic character rather than due to experimental uncertainties. So, in processing the observed-data, we widely exploit the conception of the photometric mass of a meteor body. An alternative method for estimating meteor parameters is based on the analysis of observed deceleration. The discrepancy of the estimates obtained using these two techniques is usually diminished by selecting "appropriate" values of the meteor density. However, this leads to obviously underestimated values for this density. In order to eliminate these discrepancies, it was proposed to consider a swarm of similar-size fragments instead of a single meteoroid. In this case, it is the photometric-to-dynamic mass ratio that determines the number of such fragments [2, 3].
In the present report, an analytical model of the atmospheric entry is calculated using the data of actual observations, by selecting the parameters describing deceleration and ablation of meteors along the luminous segment of the trajectory. The main difference from previous studies is that the given observations are approximated using the analytical solution of the equations of meteor physics.
The proposed general approach helps in understanding the extensive observational data. On the basis of presented mathematical model we can suggest now some cases where the discrepancy between the dynamic and photometric estimates cannot be explained even by the above-mentioned reasons. In particular, large meteors with dynamic masses exceeding the photometric mass by more than an order of magnitude were observed. Furthermore the detail calculations clearly show that the major part of the luminous segment of the trajectories of large meteors corresponds to continuous medium flow, while the condition of a free molecular flow holds outside this segment. The maximum brightness altitude is smaller than that at which a strong bow shock is formed. Therefore, we can assume that the meteor brightness under these conditions is mainly due to the emission from air in the compressed shock layer rather than due to the emission from evaporated meteor matter which is necessary for the validity of the well-known photometric formula.
Correct mathematical modeling of meteor events in the atmosphere is necessary for further estimates of the key parameters, including the extra-atmospheric mass, the ablation coefficient, and the effective enthalpy of evaporation of entering bodies. In turn, this information is needed by some applications, namely, those aimed at studying the problems of asteroid and comet security, to develop measures of planetary defense, and to determine the bodies that can reach Earth’s surface.
REFERENCES
1. C. W. Allen, Astrophysical Quantities (Athlone, London, 1973; Mir, Moscow, 1977).
2. Yu. I. Voloshchuk, B. L. Kashcheev, and V. G. Kruchinenko, Meteors and Meteoric Substance (Naukova Dumka, Kiev, 1989) [in Russian].
3. Borovicka J., Popova O.P., Nemtchinov I.V., Spurný P., Ceplecha Z. Bolides produced by impacts of large meteoroids into the Earth’s atmosphere: comparison of theory with observations I. Benešov bolide dynamics and fragmentation, Astron. and Astrophys. 1998. Vol. 334, p. 713-728.
- Abstract document
- Manuscript document
IAC-04-Q.6.02.pdf (🔒 authorized access only).
To get the manuscript, please contact IAF Secretariat.