Airborne intensified charge-coupled device observations of the 1998 Leonidshower

We have used dual coaxial microchannel plate image-intensified monochrome c harge-coupled device (CCD) detectors run at standard NTSC frame rates (30 f rames per second, fps) to study the Leonid meteor shower on 1998 November 1 7 fi-om an airborne platform at an altitude of similar to 13 km. These obse rvations were part of NASA's 1998 Leonid multi-instrument aircraft campaign (MAC). The observing systems had fields of view (width) of 16.3 degrees and 9.5 degrees, and limiting stellar sensitivities of +8.3(m) and +8.9(m). Du ring 12 h of recording, 230 meteors were detected, of which 65 were Leonid meteors. Light curves are presented for 53 of these meteors. The magnitudes at peak brightness of the meteors investigated were generally in the range from +4.0(m) to +6.0(m) The mass distribution indices for the two samples are 1.67 and 1.44, with the former being based on the wider field of view d ataset. The light curves were skewed with the brightest point towards the b eginning of the meteor trail. The F parameter for points one magnitude belo w maximum luminosity had a mean value of 0.47 for the wider field system an d 0.37 far the more sensitive narrower field system. We provide leading and trailing edge light curve slopes for each meteor as another indication of light curve shape. There were few obvious flares on the light curves, indic ating that in-flight fragmentation into a large number of grains is not com mon. There is variability in light curve shape from meteor to meteor. The l ight curves are inconsistent with single, compact body meteor theory, and w e interpret the data as indicative of a two-component dustball model with m etal or silicate grains bonded by a lower boiling point, possibly organic, substance. The variation in light curve shape may be indicative of differen ces in mass distribution of the constituent grains. We provide trail length vs. magnitude data. There is only a slight hint of a bend at +5(m) in the data, representing the difference between meteors that have broken into a c luster of grains prior to grain ablation, and those that continue to fragme nt during the grain ablation phase. Two specific meteors show interesting l ight curve features. One meteor is nebulous in appearance, with significant transverse width. The apparent light production region extends fbr 450 m f rom the center of the meteor path. Another meteor has several main fragment s, and evidence of significant separated fragments. We offer several sugges tions for improvements for the 1999 Leonid MAC light curve experiment.