POEMS Project
This describes the POEMS instrument, as it was proposed in January of 1993
for a SMEX mission by a team led by Paul
Evenson at the University of Delaware.
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Scientific Justification:
Precise measurements of the cosmic positron-electron ratio, as a function of energy
and time, are required to conquer one of the final frontiers in cosmic-ray
research. Although the total positron plus electron spectrum is relatively
well measured, the ratio of positrons to electrons is not well determined
either from measurements or from theoretical arguments. The time variations
and energy dependence of this ratio hold the key to answering many basic
questions concerning the origin, acceleration, and interstellar propagation
of galactic cosmic rays, the interaction of cosmic rays with the solar
wind (solar modulation), and the acceleration of energetic particles in
solar flares, in the solar wind, and at the outer boundaries of the heliosphere.
To address these questions we propose a Small
Explorer mission centered around a modified version of the POsitron
Electron Magnetic Spectrometer (POEMS) originally selected for the EOS
Polar Platform. POEMS will make fundamental contributions to the field
of high energy particle astrophysics. Particle astrophysics research was
cited as important for understanding violent events in the galaxy by the
Astronomy Survey Committee ("Field Report"). Position-electron measurements
specifically were recommended by the NASA Cosmic Ray Program Working Group
(CRPWG) in 1982 and reaffirmed in its 1985 update.
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Background:
POEMS was selected for flight on the first EOS polar platform and successfully
completed a Phase B definition study. In 1992 the CRPWG and the CHMOWG
noted the de-selection of POEMS from EOS for budgetary reasons as one of
the major problems facing the field. Subsequently the Space Physics Division
commissioned a study (conducted by Ball Aerospace) of the possibility of
implementing POEMS as defined for EOS on a free-flying spacecraft in low
Earth orbit. The study concluded that this was completely feasible, but
would require the use of a Taurus booster, the mass of the detector being
somewhat beyond the capability of a Pegasus. In this proposal we demonstrate
that relaxed magnetic cleanliness requirements allow a design that meets
all scientific requirements with a major reduction in mass that puts POEMS
well within the scope of a Small Explorer.
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Scientific Goals (SMEX)
We propose to make precise measurements of the energy spectra of cosmic
electrons and positrons from 20 MeV to 2 GeV, and total electrons from
300 keV to 10 GeV, - with a time resolution of approximately one month
- for a minimum of one year beginning in 1998. In addition we will make
other measurements necessary for the interpretation of the primary data.
Extension of the mission beyond one year would provide important additional
data on time-dependent aspects of our investigation.
In addition to the Magnet Spectrometer (MS), the SMEX payload includes
a second cosmic ray sensor, the Energy Extention Sensor (EES), will provide
information on the electron spectrum below 20 MeV and on the particle environment
at the spacecraft needed for interpretation of the primary data.
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Payload Team Organization (SMEX-93)
- Bartol Research Institute, Paul
A. Evenson, POEMS PI
- GSFC - Laboratory for High Energy Astrophysics, Louis
M. Barbier, Lead Co-I
- Louisiana State University, John
P. Wefel, Lead Co-I
- University of Arizona, Lunar and Planetary Laboratory, J.
Randy Jokipii, Lead Co-I
- University of Chicago, Simon
P. Swordy,
Lead Co-I
- University of Kiel, Germany, Horst
Kunow, Lead Co-I
- University of Turku, Finland, Jarmo
Torsti, Lead Co-I
- Service d'Astrophysique,
CEA/Saclay, France, Philippe Ferrando, Lead-Co-I
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Page created and updated by Jacques
L'Heureux
Last modified:
August 6, 2003
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