Invited Presentation

LiteBIRD - a future satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection

Masashi Hazumi (KEK)

LiteBIRD is a satellite to map the polarization of the cosmic microwave background (CMB) radiation over the full sky at large angular scales with unprecedented precision. Cosmological inflation, which is the leading hypothesis to resolve the problems in the Big Bang theory, predicts that primordial gravitational waves were created during the inflationary era. Measurements of polarization of the CMB radiation are known as the best probe to detect the primordial gravitational waves.
The LiteBIRD working group is authorized by the Japanese Steering Committee for Space Science (SCSS) and is supported by Japan Aerospace Exploration Agency (JAXA). It has more than 60 members from Japan, USA and Canada. Studies in the working group are in progress toward the mission definition review, with a target launch year around 2020. The scientific objective of LiteBIRD is to test all the representative inflation models that satisfy single-field slow-roll conditions and lie in the large-field regime. To this end, the requirement on the precision of the tensor-to-scalar ratio, r, at LiteBIRD is equal to or less than 0.001.
The optical system of LiteBIRD consists of a rotating half-wave plate with a diameter of 30cm and two reflective mirrors with a diameter of about 60cm. The angular resolution is half a degree at 150 GHz, which is sufficient for detecting both reionization and recombination peaks of the B-mode power spectrum. The focal plane of LiteBIRD is an array of multichroic superconducting polarimeters that are read out with high multiplexing factors in the frequency domain. This technology allows a compact focal plane with 6 frequency bands between 50 and 320 GHz. In case of TES bolometers, the total sensitivity of 2 microKarcmin is achieved with about 2000 sensors at 100mK. The cryogenic system is based on the Stirling/JT technology developed for SPICA, and the continuous ADR system shares the design with future X-ray satellites.