ИСТИНА

In this talk we will considere theoretical justifications of polarimetric measurements, early experiments for the X-ray measurements of solar and pulsar emission. Early successes, and ambiguous results will be critically accessed. Necessity of deriving the well defined background and of internal, instrumental asymmetry in measurable distributions of primary photons are discussed as well. Source morphology, strength of the source signal, geometry of reprocessing environment, strength and ordering of magnetic and photon fields - all these particularities of the real polarization measurement experiments are discussed in this talk. Despite of all mentioned difficulties we stress that polarization measurements are powerful tool that has to be used to study GRB collimated jet geometry, its content, magnetic field, emission mechanism via shocks, and/or magnetic lines annihilation, not to forget Lorentz Invariant Violation. Practical cases are considered, and conclusion are drawn on the necessity to develop Compton-scatter type polarimeters that are better suited to study polarization in the hard X-ray range of astrophysical objects emission. Target choice and experiment expectations have to be trimmed with the help of simulations and calibrations.