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LEONID DAILY NEWS: November 14, 2000



Leonid shower from space

Distribution of meteor magnitudes

Figure left: A composite of Leonid meteor images recorded by a CCD camera onboard the MSX satellite. Right: the distribution of meteor magnitudes derived from these records. Third figure on the page shows one CCD frame from the narrow angle camera with one Leonid meteor just above the airglow.

METEOR SHOWER FROM SPACE

The view from space offers a unique perspective on meteors. In a recent issue of Earth, Moon and Planets, Peter Jenniskens and David Nugent at NASA Ames Research Center, Ed Tedesco at TerraSystems, Inc., and Jayant Murthy at the Johns Hopkins University report on the first observations of a Leonid meteor shower from space.

Space based observations are uniquely suited for spectroscopy of meteors at wavelengths that are inaccessible from the ground. Space based observations are also capable of monitoring a large surface area for influx of bright Leonid fireballs. The 1997 Leonid shower was rich in such bright meteors and numerous detections were made.

One Leonid meteor from space

The image to the right is a composite of some of the 29 meteors filmed during a 48 minute period at the peak of the 1997 Leonid shower. The star background is the constellation of Aries, which gives a sense of scale. The images were taken with the UVISI instrument onboard the Midcourse Space Experiment satellite (MSX). MSX is a Ballistic Missile Defense Organization project. The Johns Hopkins Univeristy Applied Physics Laboratory developed, integrated, and operated MSX and the Ultraviolet and Visible Imagers and Spectrographic Imagers (UVISI) instrument that was used for the observations.

The satellite was programmed to watch the limb of the Earth, where the rate of meteor detections is expected to be highest, because the largest surface area is covered in a single field of view. In some of the narrow field images it is clearly seen that the fast Leonid meteors ablated above the layer of the airglow at about 87 km altitude, where most other meteors ablate. Meteors that are seen below the airglow layer are in fact closer to the satellite. Meteors in the background are significantly dimmed and do not show the gradual rise in intensity that is clear in other images. This made it possible to determine uniquely the distance to all meteors and measure their absolute brightness, defined as the meteor's brightness if it was at 100 km distance.

The observations were analysed to determine the rate of bright meteors incident on the Earth at the time of the shower. The limiting absolute magnitude for limb observations of Leonid meteors was measured at Mv = -1.5 magn. The Leonid shower magntiude population index was measured at N(m+1)/N(m) = 1.60.2 down to Mv = -7 magn., with no sign of an upper mass cut-off (Full paper - PDF).




Previous news items:
Nov. 14 - Meteor shower from space
Nov. 13 - Organic fingerprint
Nov. 12 - Train airglow chemistry
Nov. 11 - Hard bits and persisting glows
Nov. 10 - Meteoroid debris detected
Nov. 09 - New meteor picture
Nov. 08 - Spin city
Nov. 07 - Meteors affect atmospheric chemistry
Nov. 06 - Listen to this!
Nov. 04 - Fear of heights?
Nov. 03 - The pale (infra-red) dot
Nov. 02 - Twin showers
Nov. 01 - Leonids approaching Earth
Oct. 31 - Prospects for Moon Impact Studies
Oct. 30 - Comet dust crumbled less fine
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These and other results of Leonid storm research will appear in a special issue of the peer-reviewed journal "Earth, Moon and Planets", published by Kluwer Academic Publishers, the Netherlands.


 
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