Status of the Rocket Experiment Demonstration of a Soft X-Ray Polarimeter (Redsox)

The Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX) is a NASA-funded sounding rocket instrument that can make the first measurement of the linear X-ray polarization of an extragalactic source in the 0.2-0.4 keV band. We employ multilayer-coated mirrors as Bragg reflectors at the Brewster angle. By matching the dispersion of a dispersive spectrometer using critical angle transmission gratings to three laterally graded multilayer mirrors (LGMLs), we achieve polarization modulation factors over 90%. We will describe new prototyping work as well as extensions of the design for an orbital version. This work is supported in part by NASA grant 80NSSC23K0644.