  We propose to extend the investigations of the eta meson production in
nucleon-nucleon collisions by studying single and double polarization
observables. Over the last years, the eta meson has been studied at several
different experiments mainly by measurements of unpolarized total and
differential cross sections. To reveal the production mechanism, polarization
observables help to disentangle the amplitudes of the partial waves and
therefore to understand the underlying exchange processes. Analyzing powers
have been measured enabling to separate the contributing amount of some of
these amplitudes. Double polarization observables will widen the number of
accessible amplitudes and hence give further constraints to the theoretical
models. Due to the trigonometric symmetries in polarization measurements, a
symmetric detector geometry in the azimuthal angle is preferable. The WASA
detector with its 4-pi geometry for neutral and charged particles together with
the use of a frozen spin target should therefore allow to study double
polarization observables not only in vec{p}vec{p} but also in vec{p}vec{d} or
vec{d}vec{p} collisions. This first requires the development of a frozen-spin
target whereas single polarization observables can be measured directly with
the current setup.
