Large Angular Scale Polarization Survey of the Cosmic Microwave Background

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This award will fund commissioning and operations of the Cosmology Large Angular Scale Surveyor (CLASS) cosmic microwave background (CMB) polarization experiment located in the Atacama Desert in Chile. The first of two planned telescopes was recently deployed. The main science goal is to detect a polarization signal originating in a theorized rapid inflation of the universe during the first moments of the Big Bang. Broader impacts of the work include training of undergraduate students, graduate students, and postdocs. The project also has an integrated program of public outreach to engage the Baltimore public through the annual Johns Hopkins University Physics Fair, the well-established Quarknet program that trains high school teachers, and interactive planetarium shows at Baltimore city schools with large populations of under-represented minorities.Ultimately, two telescopes will make observations at frequencies of 40, 90, 150, and 220 GHz. A novel aspect of the CLASS instrumentation is that its first optical element is a variable polarization modulator (wire grid with variable offset from a flat mirror). The main science goal is to search for the inflationary gravitational wave B-mode polarization signal on angular scales of roughly 10 degrees, associated with the reionization 'bump' in the CMB angular power spectrum. Another science goal is to improve the electron-scattering optical depth of the reionization era to CMB photons by measuring the E-modes associated with the reionization signal. Development of the telescopes and other instrumentation to conduct the survey has been supported via two previous awards from NSF's Major Research Instrumentation program.