SPHiNX is a proposed gamma-ray burst (GRB) polarimeter mission operating in the energy range 50 to 600 keV with the aim of studying the prompt emission phase. The polarization sensitivity of SPHiNX reduces as the uncertainty on the GRB sky position increases. The stand-alone ability of the SPHiNX design to localize GRB positions is explored via Geant4 simulations. Localization at the level of a few degrees is possible using three different routines. This results in a large fraction (>80 % ) of observed GRBs having a negligible (<5 % ) reduction in polarization sensitivity due to the uncertainty in localization.
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.
The Polarized Gamma-ray Observer, PoGOLite, is a balloon experiment with the capability of detecting 10% polarization from a 200 mCrab celestial object between the energy-range 25–80 keV in one 6 hour flight. Polarization measurements in soft gamma-rays are expected to provide a powerful probe into high-energy emission mechanisms in/around neutron stars, black holes, supernova remnants, active-galactic nuclei etc. The “pathfinder” flight was performed in July 2013 for 14 days from Sweden to Russia. The polarization is measured using Compton scattering and photoelectric absorption in an array of 61 well-type phoswich detector cells (PDCs) for the pathfinder instrument. The PDCs are surrounded by 30 BGO crystals which form a side anti-coincidence shield (SAS) and passive polyethylene neutron shield. There is a neutron detector consisting of LiCaAlF6 (LiCAF) scintillator covered with BGOs to measure the background contribution of atmospheric neutrons. The data acquisition system treats 92 PMT signals from 61 PDCs + 30 SASs + 1 neutron detector, and it is developed based on SpaceWire spacecraft communication network. Most of the signal processing is done by digital circuits in Field Programmable Gate Arrays (FPGAs). This enables the reduction of the mass, the space and the power consumption. The performance was calibrated before the launch.