XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of
writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the
polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently
exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially-
resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics.
Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective
area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega
launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest
Observer competitive program and it is organized as a consortium across Europe with main contributions from
Italy, Germany, Spain, United Kingdom, Poland, Sweden.
In this work, it is described the Imaging Magnetograph eXperiment, IMaX, one of the three postfocal instruments of
the Sunrise mission. The Sunrise project consists on a stratospheric balloon with a 1 m aperture telescope, which will fly
from the Antarctica within the NASA Long Duration Balloon Program.
IMaX will provide vector magnetograms of the solar surface with a spatial resolution of 70 m. This data is relevant
for understanding how the magnetic fields emerge in the solar surface, how they couple the photospheric base with the
million degrees of temperature of the solar corona and which are the processes that are responsible of the generation of
such an immense temperatures.
To meet this goal IMaX should work as a high sensitivity polarimeter, high resolution spectrometer and a near
diffraction limited imager. Liquid Crystal Variable Retarders will be used as polarization modulators taking advantage of
the optical retardation induced by application of low electric fields and avoiding mechanical mechanisms. Therefore, the
interest of these devices for aerospace applications is envisaged. The spectral resolution required will be achieved by
using a LiNbO3 Fabry-Perot etalon in double pass configuration as spectral filter before the two CCDs detectors. As well
phase-diversity techniques will be implemented in order to improve the image quality.
Nowadays, IMaX project is in the detailed design phase before fabrication, integration, assembly and verification.
This paper briefly describes the current status of the instrument and the technical solutions developed to fulfil the
The SUNRISE balloon project is a high-resolution mission to study solar magnetic fields able to resolve the critical scale of 100 km in the solar photosphere, or about one photon mean free path. The Imaging Magnetograph eXperiment (IMaX) is one of the three instruments that will fly in the balloon and will receive light from the 1m aperture telescope of the mission. IMaX should take advantage of the 15 days of uninterrupted solar observations and the exceptional resolution to help clarifying our understanding of the
small-scale magnetic concentrations that pervade the solar surface. For this, IMaX should act as a diffraction limited imager able to carry out spectroscopic analysis with resolutions in the 50.000-100.000 range and capable to perform polarization measurements. The solutions adopted by the project to achieve all these three demanding goals are explained in this article. They include the use of Liquid Crystal Variable Retarders for the polarization modulation, one
LiNbO3 etalon in double pass and two modern CCD detectors that allow for the application of phase diversity techniques by slightly changing the focus of one of the CCDs.