• Fragmentation model analysis of the observed atmospheric trajectory of the Tagish Lake fireball

      Ceplecha, Zdeněk (The Meteoritical Society, 2007-01-01)
      A recently published meteoroid fragmentation model (FM) was applied to observational data on the Tagish Lake meteoric fireball. An initial mass of 56,000 kg, derived from seismic and infrasound data by Brown et al.(2002), proved to be consistent with a very low value of intrinsic ablation coefficient of 0.0009 s^2km^(-2). The average residual of the best fit to the observed light curve was +/- 0.10 stellar magnitude. The apparent ablation coefficient varied from 0.0009 to 1.52 s^2 km^(-2), with an average value of 0.054 s^2 km^(-2) (determined by the gross fragmentation [GF] model). The FM found 33 individual fragmentation events during the penetration of the 56,000 kg initial mass of the Tagish Lake meteoroid through the atmosphere, with five of the events fragmenting more than 10% of the instantaneous mass of the main body. The largest event fragmented 88% of the mass of the main body at a height of 34.4 km. The velocity of the main body mass of 2660 kg at a height of 29.2 km (the last observed light) was 13.1 km/s. Strong fragmentation at heights lower than 29.2 km is very probable. The extreme fragmentation process of the Tagish Lake meteoroid puts its classification well outside the IIIB type in the direction of less cohesive bodies. The light curve could not be explained at all by making use of only the apparent ablation coefficient and apparent luminous efficiency.
    • Stardust—An artificial, low-velocity "meteor" fall and recovery: 15 January 2006

      Revelle, D. O.; Edwards, W. N. (The Meteoritical Society, 2007-01-01)
      On January 15, 2006, Stardust, a man-made space capsule, plummeted to Earth for a soft landing after spending seven years in space. Since the expected initial speed of the body was about 12.9 km/s, a four-element ground-based infrasound array was deployed to Wendover, Nevada, USA, to measure the hypersonic booms from the re-entry. At a distance of ~33 km from the nominal trajectory, we easily recorded the weak acoustic arrivals and their continued rumbling after the main hypersonic boom arrival. In this paper, we report on subsequent analyses of these data, including an assessment of the expected entry characteristics (dynamics, energetics, ablation and panchromatic luminosity, etc.) on the basis of a bolide/meteor/fireball entry model that was specifically adapted for modeling a re-entering man-made object.Throughout the infrasonic data analyses, we compared our results for Stardust to those previously obtained for Genesis. From the associated entry parameters, we were also able to compute the kinetic energy density conservation properties for the propagating line source blast wave and compared the inviscid theoretical predictions against observed ground-based infrasound amplitude and wave period data as a function of range. Finally, we made a top-down bottom-up assessment of the line source wave normals propagating downward into the complex temperature/sound speed and horizontal wind speed environment during January 15, 2006. This assessment proved to be generally consistent with the signal processing analysis and with the observed time delay between the known Stardust entry and the time of observations of infrasound signals, and so forth.