  This thesis focuses on X-ray polarimetry and its recent resurgence due to the
NASA/ASI Imaging X-ray Polarimetry Explorer (IXPE) mission launched in December
2021. It aims to address two critical tasks: in-orbit calibrations and
observing faint extended celestial sources. For in-orbit calibrations, IXPE
carries polarized and unpolarized calibration sources because known celestial
sources, like the Crab Nebula, aren't suitable due to variability. Tests were
performed on Flight Models of these calibration sources, ensuring their
functionality in thermal vacuum when combined with IXPE detectors. Concerning
observing faint extended sources, instrumental and diffuse backgrounds pose
challenges. The impact of various background sources, such as instrumental,
diffuse Galactic plane emission, and cosmic X-ray background, on X-ray
polarimetry of faint, extended sources was examined. The feasibility study also
covered observing two extended sources: the Tycho supernova remnant and the
molecular clouds of the Sgr A complex. Monte Carlo simulations were employed to
evaluate the detectability of polarization. Results show that the on-board
calibration system will assess and verify the GPD's functionality in orbit.
Background mitigation techniques will be required for faintest extended
sources. For sources like Cas A, Tycho, and PSW MSH 15-52, background effects
are negligible. In conclusion, the IXPE mission opens up spatially resolved
X-ray polarimetry, enabling the determination of polarization angles and
degrees. Preliminary data after launch indicates that on-board calibration
sources are performing as expected, and imaging capabilities meet requirements.
This research is essential for advancing X-ray polarimetry and understanding
high-energy celestial sources.
