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Instrument: CELIAS : Charge, Element, and Isotope Analysis System
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Associated Platforms
SOHO

Spectral/Frequency Information
Wavelength Keyword: Ultraviolet
Spectral/Frequency Coverage/Range: 17-70 nm

Related Data Sets
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Description
The Charge, Element, and Isotope Analysis System (CELIAS) instrument is
designed to study the composition of the solar wind (SW) and of solar and
interplanetary energetic particles on SOHO. SOHO is a project of international
cooperation between ESA and NASA. The CELIAS instrument consists of three
different sensors with associated electronics, which are optimized each for a
particular aspect of ion composition. These aspects are the elemental,
isotopic, and ionic charge composition of SW or energetic ions emanating from
the Sun. In addition, the Solar EUV Monitor (SEM) has been included into CELIAS
for monitoring the absolute EUV flux from the Sun.

The CELIAS instrument consists of three different sensor units (CTOF, MTOF, and
STOF) coupled to a Digital Processing Unit (DPU). The energy ranges of the SOHO
particle instruments, the CELIAS ion sensors together with the COSTEP /ERNE
energetic particle experiments, cover a very wide range (large version) in
nuclear mass and energy space.

All three CELIAS sensors employ electrostatic deflection systems in combination
with time-of-flight (TOF) measurements of the impinging particles. The CTOF and
STOF sensors employ also silicon solid state detectors to determine the
residual energy of particles. Thus for these two sensors the quantities energy
per charge, E/Q, time-of-flight (TOF), and energy, E, are determined for the
incoming particles. CTOF and STOF are aimed at different energy ranges, CTOF
being devoted to solar wind and low energy suprathermal ions, while STOF is
devoted to higher energy suprathermal and low energy solar energetic particles.
The MTOF sensor is a high resolution retarding potential mass analyzer with a
quadrupol electric field configuration, which will be able not only to measure
the composition of the less abundant elements in the solar wind, but also the
isotopic composition of the more abundant heavy ions.

The solar EUV monitor, SEM, is structurally connected with STOF. SEM consists
basically of a diffraction grating in front of a set of three absolutely
calibrated silicon light diodes, which are covered with an aluminum filter. The
diodes are placed at the zero - and first order diffraction image of the Sun in
order to isolate the 30.4 nm He II line.

The digital processing unit, DPU, serves all three sensors by fully handling
the communications with the spacecraft. It receives rate and pulse-height data
from each sensor, compresses, stores and formats it for conveying the data to
the S/C telemetry. It also handles the experiment control through the
commanding system and surveys the CELIAS housekeeping data.

For more information, see:
http://www.space.unibe.ch/soho/

Online Resources
http://www.space.unibe.ch/soho/

Instrument Logistics
Instrument Start Date: 1995-12-02
Instrument Owner: Max Planck Institut fur Extraterrestrische Physik
Universiy of Bern, Switzerland
Max Planck Institut fur Aeronomie
University of Maryland
Technische Universitat Braunschweig
University of Southern California