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18%
Dalton
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28%
Lavoisier
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18%
Avogadro
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36%
Gay-Lussac

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Which is your favourite NASA Facility?
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21%
NASA Stennis Space Center
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NASA JPL Goldstone Facility
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66%
NASA Kennedy Space Center
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7%
NASA Goddard Facility
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Marshall Space Flight Center

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Hubble Provides Clear Images Of Saturn's Aurora

This is the first image of Saturn's ultraviolet aurora taken by the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope in October 1997, when Saturn was a distance of 810 million miles (1.3 billion kilometers) from Earth. The new instrument, used as a camera, provides more than ten times the sensitivity of previous Hubble instruments in the ultraviolet. STIS images reveal exquisite detail never before seen in the spectacular auroral curtains of light that encircle Saturns north and south poles and rise more than a thousand miles above the cloud tops.

Credit:

J.T. Trauger (Jet Propulsion Laboratory) andNASA/ESA


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USA Space Shuttle in Launch.

Image Credits : NASA
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KNOWING NASA'S CLUSTER SATELLITE

The Cluster II mission is an in-situ investigation of the Earth's magnetosphere using four identical spacecraft simultaneously. It will permit the accurate determination of three-dimensional and time-varying phenomena and will make it possible to distinguish between spatial and temporal variations.

The interaction between the solar wind and the magnetosphere is a key element in the Solar Terrestrial Science Programme (STSP). One example of this interaction is the direct entry of solar wind particles through the polar cusps. The polar cusps are two magnetic funnels, one in each hemisphere, which focus the solar wind particles. The solar wind particles enter the exterior cusp, which has a diameter of approximately 50 000 km, and then follow the converging magnetic field down to the ionosphere where the cusp size is around 500 km. This converging magnetic field allows the study of a very large area of the magnetopause through a limited region of space inside the cusps.

Another example of solar wind/magnetosphere interaction is the acceleration of plasma in the magnetotail during substorms. The magnetotail is a large reservoir of both solar wind and ionospheric particles which, under some circumstances (the reversal of the interplanetary magnetic field from north to south, for example) releases a large quantity of particles towards the Earth. Both mechanisms—particles entering the polar cusps and the substorms—produce aurorae when the participating particles (electrons and ions) hit the neutral gas of the atmosphere. When these particles are particularly energetic they can have a dramatic effect on human activities, disrupting electrical power and telecommunications or causing serious anomalies in the operation of satellites, especially those in geostationary orbit.

Cluster II is determining the physical processes involved in the interaction between the solar wind and the magnetosphere by visiting key regions like the polar cusps and the magnetotail. The four Cluster spacecraft is mapping in three dimensions the plasma structures contained in these regions. The simultaneous four-point measurements also allow differential plasma quantities to be derived for the first time. For example, the density of current flowing around the spacecraft is derived from the magnetic field measurements using Ampere's law.

Cluster II's main goal is to study the small-scale plasma structures in space and time in the key plasma regions:

1 ) solar wind and bow shock
2 ) magnetopause
3 ) polar cusp
4 ) magnetotail
5 ) auroral zone
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