LiteBIRD

LiteBIRD (Light satellite for the studies of B-mode polarization and Inflation from cosmic background radiation) is a planned space mission led by the Japan Aerospace Exploration Agency (JAXA) to measure the polarization of the cosmic microwave background (CMB) with the aim of detecting primordial B-mode polarization produced by gravitational waves from the early universe. By observing the CMB over a wide range of microwave frequencies, LiteBIRD seeks to separate the CMB signal from polarized foregrounds and map the full-sky polarization with high sensitivity.

The mission architecture comprises three telescope assemblies—the Low Frequency Telescope (LFT), the Medium Frequency Telescope (MFT) and the High Frequency Telescope (HFT)—that share a common focal plane populated by thousands of polarization-sensitive detectors. The detectors use superconducting technology such as transition-edge sensors or kinetic inductance detectors. A continuously rotating half-wave plate is planned to modulate the polarization signal, helping reduce instrumental systematics. LiteBIRD is designed to operate from a stable space environment, such as a Sun–Earth L2 orbit, to enable long, uniform observations.

Science goals include constraining the tensor-to-scalar ratio r to the level of a few times 10^-3, providing strong tests of inflationary models and the generation of primordial gravitational waves. The mission also yields high-fidelity full-sky maps of CMB polarization and foreground polarization, contributing to Galactic science and foreground modeling. It is an international collaboration involving research institutions across Asia, Europe and North America.

Status and timeline: LiteBIRD was selected by JAXA for development and is planned for launch in the early 2030s.