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In this note, we discuss the prospect of accurate measurements of cosmic microwave background (CMB) polarization rotation with future surveys. We focus on instrumental issues, analyzing the required improvements in detection methods and calibration procedures, and discuss the impact of these requirements in the design and optimization of forthcoming CMB polarimeters.

The 15${}^{\mathrm{\text{th}}}$ International Workshop on Polarized Source Targets and Polarimeters was held at the University of Virginia, Charlottesville during September 9–13, 2013. It was sponsored jointly by the University of Virginia, Jefferson Laboratory and the International Spin Physics Committee. A summary of the workshop was presented.

Advances in astronomy are intimately linked to advances in digital signal processing (DSP). This special issue is focused upon advances in DSP within radio astronomy. The trend within that community is to use off-the-shelf digital hardware where possible and leverage advances in high performance computing. In particular, graphics processing units (GPUs) and field programmable gate arrays (FPGAs) are being used in place of application-specific circuits (ASICs); high-speed Ethernet and Infiniband are being used for interconnect in place of custom backplanes. Further, to lower hurdles in digital engineering, communities have designed and released general-purpose FPGA-based DSP systems, such as the CASPER ROACH board, ASTRON Uniboard, and CSIRO Redback board. In this introductory paper, we give a brief historical overview, a summary of recent trends, and provide an outlook on future directions.

High-resolution Airborne Wide-band Camera (HAWC$+$) is the facility far-infrared imager and polarimeter for SOFIA, NASA’s Stratospheric Observatory for Infrared Astronomy. It is designed to cover the portion of the infrared spectrum that is completely inaccessible to ground-based observatories and which is essential for studies of astronomical sources with temperatures between tens and hundreds of degrees Kelvin. Its ability to make polarimetric measurements of aligned dust grains provides a unique new capability for studying interstellar magnetic fields. HAWC$+$ began commissioning flights in April 2016 and was accepted as a facility instrument in early 2018. In this paper, we describe the instrument, its operational procedures, and its performance on the observatory.

We introduce Probing Radio Intensity at high-Z from Marion (PRI^ZM), a new experiment designed to measure the globally averaged sky brightness, including the expected redshifted 21cm neutral hydrogen absorption feature arising from the formation of the first stars. PRI^ZM consists of two dual-polarization antennas operating at central frequencies of 70 and 100MHz, and the experiment is located on Marion Island in the sub-Antarctic. We describe the initial design and configuration of the PRI^ZM instrument that was installed in 2017, and we present preliminary data that demonstrate that Marion Island offers an exceptionally clean observing environment, with essentially no visible contamination within the FM band.

The RHIC polarized proton collider employs polarimeters in each of the blue and yellow rings that utilize the analyzing power in p-carbon elastic scattering in the Coulomb Nuclear Interference (CNI) region to measure the absolute beam polarization. These are calibrated by the polarized hydrogen jet target that measures the absolute beam polarization in pp elastic scattering in the CNI region. This paper describes the status and performance of these polarimeters in the FY09 run which included both a 250 GeV/c and 100 GeV/c physics data taking period. We will describe some of the difficulties encountered and the efforts underway to improve the performance in better energy resolution, rate handling capability, and reduced systematic uncertainties.

Phase I of the Q/U Imaging ExperimenT (QUIET) measures the Cosmic Microwave Background polarization anisotropy spectrum at angular scales 25 ≲ l ≲ 1000. QUIET has deployed two independent receiver arrays. The 40-GHz array took data between October 2008 and June 2009. The 90-GHz array was deployed in June 2009 and observations are ongoing. Described in this proceeding are the instrument, analysis procedures, and expected science reach for the QUIET Phase I arrays. We also briefly discuss the science forecasts for QUIET Phase II in which arrays roughly an order-of-magnitude larger will be deployed.