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Leonids animations
The Leonids Meteoroid Shower occurs annually, each November. Every 33 years or so, throughout recorded history, it is particularly significant and spectacular. This year the event is centred over Europe. This set of synthetic images help to explain what is happening and the possible effect on spacecraft that are exposed to the stream of meteors.

Please note: You may use these animations, provide you clearly credit ESA when you do.

These pictures may not be used to state or imply the endorsement by ESA or any ESA employee of a commercial product, process or service, or used in any other manner that might mislead; if recognisable persons appear in this picture, use for commercial purposes may infringe their rights. If this picture is to be used in advertising or any commercial promotion, layout and copy should therefore be submitted to ESA beforehand for approval.

The spectacular show every 33 years is linked to the return visits of the parent comet of the Leonid meteor showers, the periodic comet Tempel-Tuttle.

Have a look at the video (comet.mpg 1.3MB)

As the comet nears the sun, the heat of the sun boils off debris particles from the comet on the sun-facing side which forms a trail in the wake of the comet. This last happened for Tempel-Tuttle in spring 1998 with the closest approach to the sun 14 February 1998.

Have a look at the video (comet_approaching_sun.mpg 1.2MB)

The trail of debris, made up of very fine particles of ice and material, is travelling extremely fast, at a speed relative to Earth of 71 kilometers per second. This debris trail is several earth diameters across. On 17 November the Earth crosses the comet's wake, so scientists predict that extremely high numbers of meteors will be visible.

Have a look at the video (high_speed_comet.mpg 1.6MB)

The trail of debris move in the opposite direction to the Earth's Orbit, therefore the speed relative to Earth is so high.

Have a look at the video (orbit.mpg 1.9MB)

The meteoroids impact the Earth's atmosphere which enables us to determine the number of meteoroids from a count of trails seen from a particular position on Earth per hour. Rates as high as 150000 per hour were seen for the last Leonids event in 1966. These trails are the result of burn up in the atmosphere of the larger particles. Of course there could also be many very small particles which do not get counted because they are too small to make trails, but could still penetrate spacecraft and create significant amounts of plasma.

Have a look at the video (shower.mpg 1.1MB)

These very small particles can impact any area of a spacecraft facing  the stream. The velocity of the stream is so high that any surface would be penetrated. ESA's Olympus spacecraft, shown here, was probably impacted by the yearly Perseids in August of 1993 on its solar arrays,  which are generally the largest exposed area. Normally the solar arrays would be almost parallel to the Leonids and if penetration is in a critical  area it can do significant damage. There is also a very significant production of plasma, whose potential current is proportional to the velocity of impact to the power of 4.5, a very large value. This plasma may enter the electronics and cause difficulties. In the case of Olympus, the plasma probably entered via the launch umbilical and through a sun sensor. In this clip the plasma results in Olympus moving off station.

Have a look at the video (plasma.mpg 4.5MB)

In order to protect its mirror, the NASA/ESA Hubble Space Telescope will be turned away from the stream and the area of the exposed solar arrays will be minimised. For communications satellites, it is desirable to minimise the solar array cross-section and shield any sensitive equipment by orientation of the spacecraft for approximately two hours at the peak of the event. Of course, these actions may interfere with normal services which in some cases will not be possible. Impacts and effects are a result of probabilities of impact which is proportional to the stream rate.

Have a look at the video (hubble.mpg 2.3MB)