Atmospheric behavior and extreme beginning heights of the thirteen brightest photographic Leonid meteors from the ground-based expedition to China

Precise atmospheric trajectories including dynamic and photometric data on thirteen of the brightest Leonid fireballs have been determined from the do uble-station photographic observations of Leonid meteors during the ground- based expedition to China in 1998 November. The expedition was organized as a collaboration between the Dutch and Chinese Academy of Sciences and was supported by the Leonid multi-instrument aircraft campaign (MAC) program (J enniskens and Butow, 1999). All data presented here were taken at Xinglong Observatory and at a remote station, Lin Ting Kou near Beijing, on the nigh t of 1998 November 16/17. At the Xinglong station, photographic cameras wer e accompanied by an all-sky television camera equipped with an image intens ifier and 15 mm fish-eye objective in order to obtain precise timings for a ll observed meteors up to magnitude +2. Whereas beginning heights of photog raphed meteors are all lower than 130 km, those observed by the all-shy tel evision system are at similar to 160 km, and for three brightest events, ev en >180 km. Such high beginnings for meteors have never before been observe d. We also obtained a precise dynamic single-body solution for the Leonid m eteor 98003, including the ablation coefficient, which is an important mate rial and structural quantity (0.16 s(2) km(-2)). From this and from known p hotometry, we derived a density of this meteoroid of 0.7 g/cm(3). Also, all PE coefficients indicate that these Leonid meteors belonged to the firebal l group IIIB, which is typical for the most fragile and weak interplanetary bodies. From a photometric study of the meteor lightcurves, we found two t ypical shapes of light curves for these Leonid meteors.