Then, in 1966, a spectacular meteor storm was seen over the Americas.
Historical notes were gathered thus noting the Leonids back to 900AD.
Radar studies showed the 1966 storm included a relatively high percentage of smaller particles while 1965's lower activity had a much higher proportion of larger particles.
In 1981 Donald K. Yeomans of the Jet Propulsion Laboratory reviewed the history of meteor showers for the Leonids and the history of the dynamic orbit of Comet Tempel-Tuttle.
A graph from it was adapted and re-published in Sky and Telescope.
It showed relative positions of the Earth and Tempel-Tuttle and marks where Earth encountered dense dust.
This showed that the meteoroids are mostly behind and outside the path of the comet, but paths of the Earth through the cloud of particles resulting in powerful storms were very near paths of nearly no activity.
But overall the 1998 Leonids were in a favorable position so interest was rising.

Leading up to the 1998 return, an airborne observing campaign was organized to mobilize modern observing techniques by Peter Jenniskens at NASA Ames Research Center.
There were also efforts to observe impacts of meteoroids, as an example of transient lunar phenomenon, on the Moon in 1999.
A particular reason to observe the Moon is that our vantage from a location on Earth sees only meteors coming into the atmosphere relatively close to us while impacts on the Moon would be visible from across the Moon in a single view.
The sodium tail of the Moon tripled just after the 1998 Leonid shower which was composed of larger meteoroids (which in the case of the Earth was witnessed as fireballs.)
However, in 1999 the sodium tail of the Moon did not change from the Leonid impacts.

Research by Kondrat'eva, Reznikov and colleagues at Kazan University had shown how meteor storms could be accurately predicted, but for some years the worldwide meteor community remained largely unaware of these results.
The work of David J. Asher, Armagh Observatory and Robert H. McNaught, Siding Spring Observatory and independently by Esko Lyytinen in 1999, following on from the Kazan research, is considered by most meteor experts as the breakthrough in modern analysis of meteor storms.
Whereas previously it was hazardous to guess if there would be a storm or little activity, the predictions of Asher and McNaught timed bursts in activity down to ten minutes by narrowing down the clouds of particles to individual streams from each passage of the comet, and their trajectories amended by subsequent passage near planets.
However, whether a specific meteoroid trail will be primarily composed of small or large particles, and thus the relative brightness of the meteors, was not understood.
But McNaught did extend the work to examine the placement of the Moon with trails and saw a large chance of a storm impacting in 1999 from a trail while there were less direct impacts from trails in 2000 and 2001 (successive contact with trails through 2006 showed no hits.)
Then, in 1966, a spectacular meteor storm was seen over the Americas. Historical notes were gathered thus noting the Leonids back to 900AD. Radar studies showed the 1966 storm included a relatively high percentage of smaller particles while 1965's lower activity had a much higher proportion of larger particles. In 1981 Donald K. Yeomans of the Jet Propulsion Laboratory reviewed the history of meteor showers for the Leonids and the history of the dynamic orbit of Comet Tempel-Tuttle. A graph from it was adapted and re-published in Sky and Telescope. It showed relative positions of the Earth and Tempel-Tuttle and marks where Earth encountered dense dust. This showed that the meteoroids are mostly behind and outside the path of the comet, but paths of the Earth through the cloud of particles resulting in powerful storms were very near paths of nearly no activity. But overall the 1998 Leonids were in a favorable position so interest was rising.
Leading up to the 1998 return, an airborne observing campaign was organized to mobilize modern observing techniques by Peter Jenniskens at NASA Ames Research Center. There were also efforts to observe impacts of meteoroids, as an example of transient lunar phenomenon, on the Moon in 1999. A particular reason to observe the Moon is that our vantage from a location on Earth sees only meteors coming into the atmosphere relatively close to us while impacts on the Moon would be visible from across the Moon in a single view. The sodium tail of the Moon tripled just after the 1998 Leonid shower which was composed of larger meteoroids (which in the case of the Earth was witnessed as fireballs.) However, in 1999 the sodium tail of the Moon did not change from the Leonid impacts.
Research by Kondrat'eva, Reznikov and colleagues at Kazan University had shown how meteor storms could be accurately predicted, but for some years the worldwide meteor community remained largely unaware of these results. The work of David J. Asher, Armagh Observatory and Robert H. McNaught, Siding Spring Observatory and independently by Esko Lyytinen in 1999, following on from the Kazan research, is considered by most meteor experts as the breakthrough in modern analysis of meteor storms. Whereas previously it was hazardous to guess if there would be a storm or little activity, the predictions of Asher and McNaught timed bursts in activity down to ten minutes by narrowing down the clouds of particles to individual streams from each passage of the comet, and their trajectories amended by subsequent passage near planets. However, whether a specific meteoroid trail will be primarily composed of small or large particles, and thus the relative brightness of the meteors, was not understood. But McNaught did extend the work to examine the placement of the Moon with trails and saw a large chance of a storm impacting in 1999 from a trail while there were less direct impacts from trails in 2000 and 2001 (successive contact with trails through 2006 showed no hits.)
Leonids