Mission Name Polar LASP Instruments TIMAS: The Toroidal Imaging Mass-Angle Spectrograph Principal Investigators: E.G. Shelley & W.K. Peterson Destination   Launch Date February 24th, 1996 Launch Location Vandenberg Air Force Base Launch Vehicle Delta II Mission Duration   Mission Description/ LASP involvement   LASP Divisions Involved Science LASP Mission Web Page http://lasp.colorado.edu/timas/ Official Mission Web Page http://pwg.gsfc.nasa.gov/polar/

The region over the poles of the Earth is one of the most important regions of space that is studied by the ISTP Project. The Polar spacecraft was launched on February 24, 1996, to obtain data from both high- and low-altitude perspectives of this active region of geospace. High above the poles the particles of the solar wind and the energy of the wind can find their way into the magnetosphere. At lesser altitudes energy is transferred from electric fields and electromagnetic waves to electrons that then plunge into the atmosphere to create the aurora. At mid-altitudes nearer the equator the satellite passes through the Earth's trapped radiation, the Van Allen belts. Out of the polar ionosphere flows plasma to populate the magnetosphere. Through this region particles and energy flow from the geomagnetic tail to the atmosphere. Thus the instruments on the Polar satellites see a lot of action in the various plasma parameters that they measure.

Data for scientific studies are obtained not only from instruments on Polar but also from the fleet of other ISTP satellites and collaborating missions, supported by a large array of ground-based instruments. The Polar science team expects to measure and learn how the solar wind plasma energy enters into the magnetosphere through the polar cusp on the dayside of the magnetosphere. The scientists will determine the mechanisms that cause the ionospheric plasma outflow. They will discern the importance and characteristics of various processes that accelerate the aurora-producing particles. They will investigate the many ways in which energy and momentum are exchanged between the collisionless plasmas and with the electromagnetic fields accessible to the Polar spacecraft. From the images they will determine the rate of energy input into the atmosphere from auroral particles and their effects on the atmosphere.

(information taken from http://pwg.gsfc.nasa.gov/polar/overview.shtml)

The science objectives of the Toroidal Imaging Mass-Angle Spectrograph (TIMAS) are to investigate :

• The transfer of solar wind energy and momentum to the magnetosphere,
• The interaction between the magnetosphere and the ionosphere,
• The transport processes that distribute plasma and energy throughout the magnetosphere, and
• The interactions that occur as plasmas of different origins and histories mix and interact.

In order to meet these objectives the TIMAS instrument measures virtually the full three-dimensional velocity distribution functions of all major magnetospheric ion species with one-half spin period time resolution.