  LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and
Inflation from cosmic background Radiation Detection, is a space mission for
primordial cosmology and fundamental physics. The Japan Aerospace Exploration
Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class
(L-class) mission, with an expected launch in the late 2020s using JAXA's H3
rocket. LiteBIRD is planned to orbit the Sun-Earth Lagrangian point L2, where
it will map the cosmic microwave background (CMB) polarization over the entire
sky for three years, with three telescopes in 15 frequency bands between 34 and
448 GHz, to achieve an unprecedented total sensitivity of 2.2$\mu$K-arcmin,
with a typical angular resolution of 0.5$^\circ$ at 100 GHz. The primary
scientific objective of LiteBIRD is to search for the signal from cosmic
inflation, either making a discovery or ruling out well-motivated inflationary
models. The measurements of LiteBIRD will also provide us with insight into the
quantum nature of gravity and other new physics beyond the standard models of
particle physics and cosmology. We provide an overview of the LiteBIRD project,
including scientific objectives, mission and system requirements, operation
concept, spacecraft and payload module design, expected scientific outcomes,
potential design extensions and synergies with other projects.
