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Quick Facts: Polar Toroidal Imaging Mass-Angle Spectrograph (TIMAS)

Mission Introduction

Polar Spacecraft

Polar was launched to observe the polar magnetosphere and, as its orbit precessed with time, it observed the equatorial inner magnetosphere and progressed toward an extended southern hemisphere campaign. (Courtesy NASA/GSFC)

TIMAS was one of several instruments on the POLAR spacecraft, which was one of two spacecraft in NASA’s Global Geospace Science (GGS) program. GGS is, in turn, part of the International Solar-Terrestrial Physics (ISTP) program. 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 saw a lot of action in the various plasma parameters that they measured.

Data for scientific studies have been 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 sought 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 wanted to determine the mechanisms that cause the ionospheric plasma outflow, the importance and characteristics of various processes that accelerate the aurora-producing particles, and 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 received, they will determine the rate of energy input into the atmosphere from auroral particles and their effects on the atmosphere.

LASP Roles

TIMAS instrument

The Toroidal Imaging Mass-Angle Spectrograph (TIMAS) was a novel 3-D ion mass spectrograph which was optimized for the POLAR mission. (Courtesy LASP)

LASP provided:

  • The Toroidal Imaging Mass-Angle Spectrograph (TIMAS)
  • TIMAS Principal Investigators, E.G. Shelley & W.K. Peterson

LASP Instrument

The science objectives of the Toroidal Imaging Mass-Angle Spectrograph (TIMAS) were 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
  • The interactions that occur as plasmas of different origins and histories mix and interact

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

For more information about the TIMAS instrument, see:

Quick Facts

Launch date: February 24, 1996
Launch location: Vandenberg Air Force Base
Launch vehicle: Delta II
Mission target: Earth orbit
Mission duration: 12 years
Other key dates:

  • End of data acquisition: April 16, 2008

Other organizations involved:

  • Lockheed Martin Palo Alto Research Laboratory
  • Physikalisches Institut, University of Bern, Switzerland
  • Southwest Research Institute
  • Space Sciences Laboratory, University of California, Berkeley
  • Mullard Space Science Laboratory, University College London