Measurements of the X-ray polarizations of astronomical sources have not been obtained for over 40 years.  There has been substantial progress in the last 10 years toward new X-ray polarimeters in several countries, including China.  In the United States, NASA is developing an X-ray polarimetric mission for flight in 2014 as a small explorer (SMEX): the Gravitation and Extreme Magnetism SMEX (GEMS).  The primary detector on GEMS operates in the 2-8 keV band.  The instrumentation and mission will be described, along with current progress on its development.  In parallel, an approach that could be used to measure soft X-ray polarizations is under investigation at MIT.  This approach is based on using multilayer coated optics and gratings in combination to provide measurements in the 0.2-0.8 keV band.

Dr. Marshall is a Principal Research Physicist at the Massachusetts Institute of Technology (MIT), in the Kavli Instite for Astrophysics and Space Research.  He obtained his S.B. in Physics from MIT in 1978 and a Ph.D. in Astronomy from Harvard University in 1983.  He was a post-doctoral fellow at the Space Telescope Science Institute and was a software scientist on the Extreme Ultraviolet Explorer project at the University of California, Berkeley.  He is currently a calibration scientist in the Chandra X-ray Center, specializing in the calibration of the High Energy Transmission Grating Spectrometer and cross-calibration with other X-ray observatories.