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Instrument: TIMAS : Toroidal Imaging Mass-Angle Spectrograph
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The Toroidal Imaging Mass-Angle Spectrograph (TIMAS) instrument measures the
full three-dimensional velocity distribution functions of all major
magnetospheric ion species with one-half spin period time resolution. The TIMAS
is a first order double focusing (angle and energy), imaging spectrograph that
simultaneously measures all mass per charge components from 1 AMU/e to greater
than 32 AMU/e over a nearly 360 degrees by 10 degree instantaneous
field-of-view in 20 milliseconds. Mass per charge is dispersed radially on an
anular microchannel plate detector and the azimuthal position on the detector
is a map of the instantaneous 360 degrees field of view. With the rotation of
the spacecraft, the TIMAS sweeps out a 4pi solid angle image in a half spin
period. The energy per charge range from l5eV/e to 32 keV/e is covered in 28
non-contiguous steps spaced approximately logarithmically with adjacent steps
separated by about 30%. In order to handle the large volume of data within the
telemetry limitations the distributions are compressed to varying degrees in
angle and energy, log-count compressed and then further compressed by a
lossless technique. This data processing task is supported by two SA3300
microprocessors. The voltages (up to + 5 kV) for the tandem toroidal
electrostatic analyzers are supplied from common high voltage supplies using
optically controlled series-shunt regulators.

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Instrument Logistics
Instrument Start Date: 1996-02-24
Instrument Owner: Lockheed Martin Missiles & Space Company
Southwest Research Institute
Mullard Space Science Laboratory, University College, UK
University of Berne, Switzerland