GroundBIRD - pioneer experiment towards satellite mission to understand begin of the universe

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We have developed CMB (cosmic microwave background radiation) telescope ``GroundBIRD'' which aims to detect a signal from the inflationary universe. Discovery of the signal was claimed by the BICEP2 expriment while it was not discovered when we accepted this grant program. An importance of the GroundBIRD became high because our large-sky coverage (about 10 times larger than others) will probe the ever-presence of the primordial gravitatinal waves which is the source of the signal.Two important key technologies were established: achievement of 0.23 Kelvin condition on the high-speed rotation system at 20 revolution per minute, and pseudo-observation of CMB polarization by using superconducting detectors in the laboratory. We achieved milestones to achieve the large-sky coverage from the ground.