The Italian Polarimetry Programmes

The Gas Pixel Detector is a new generation X-ray polarimeter based on photoelectric effect that has been developed by INFN of Pisa and INAF/IASF of Rome. Its expected performances have been recently supported by the measurement of the modulation factor at a few keV, namely in the energy range of maximum interest. About 80% of the sensitivity expected on the basis of a Monte Carlo software are achieved with the current prototype, hence definitely proving the feasibility of X-ray photoelectric polarimetry with the GPD. Its advanced status of development allows to plan its use in the near future space missions and three proposals have passed a certain level of selection by the Italian and European space agencies. Two scenarios have emerged: the first is a small pathfinder mission, able to measure the polarization of gala ctic and bright extragalactic sources in a few days of observation with a low-cost X-ray telescope, while the second is the introduction of this device in the focal plane of a large international obs ervatory, which would make accessible even the faint extragalactic sources. Here we briefly summar ize both these opportunities.