arXiv subjects

LiteBIRD Collaboration

Publications and source records attributed to LiteBIRD Collaboration.

5 recordsLinked to original sources

arXiv2026

LiteBIRD Mission Overview after Mission Reformation

LiteBIRD is a JAXA-led space mission designed to produce all-sky microwave polarization maps. Its primary science goal is to test representative inflationary models by measuring the cosmic microwave background $B$-mode polarization generated by primordial gravitational waves, while also providing new insights into cosmology, particle physics, and astrophysics. The mission concept has been updated following the reformation activities initiated after the Mission Definition Review in 2024. The current concept preserves the central scientific objectives, while simplifying the payload configuration: a single telescope covers 12 frequency bands with band centers spanning 40 to 402~GHz, corresponding to an optical coverage of 34--448~GHz. The telescope is a cross-Dragone reflector with a 500~mm aperture diameter, cooled to approximately 5~K and coupled to transition-edge-sensor bolometer arrays operated at 0.1~K. LiteBIRD will observe from a Lissajous orbit around the Sun--Earth L2 point during a nominal 3-year survey. More specifically, the primary scientific objective is to achieve total uncertainty in the tensor-to-scalar ratio of $\delta r < 0.002$ (68\% C.L.), including contributions from foreground residuals, statistical uncertainties, instrumental systematics, and margin contingency. The corresponding map-noise requirements are specified separately for the low-, mid-, and high-frequency ranges over the reionization and recombination multipole ranges. This sensitivity makes LiteBIRD unique not only for inflationary science but also for a broad range of scientific investigations probing the history of both the early and late Universe, as well as for astrophysical processes, including Galactic science. This paper summarizes the scientific objectives, updated payload and instrument concepts, observation strategy, and ground segment plans.

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arXiv2026

Setting requirements on out-of-band rejection for next-generation CMB experiments. Application to the LiteBIRD instrument

Next-generation cosmic microwave background experiments have very stringent constraints to achieve the required sensitivity to target polarization $B$ modes. In this work, we intend to set requirements on the out-of-band rejection level, with out-of-band referring to frequencies outside the telescope band-pass. The method developed is applied to the LiteBIRD Medium and High Frequency Telescopes. In order to determine the impact of out-of-band power, we model the instrument's optical response and the spectral emissions of the sky and of the instrument itself. This allows us to propagate optical power inside the telescope. Using this tool, we address both the impact of out-of-band power on the detection chain and on the thermal heat load, together with the impact on the process of separation between astrophysical components. The role of additional static power as well as dynamic power variations is studied. The requirement derived consist in attenuation factors (in dB) in frequency subdomains. They will be used to design the telescope filters.

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arXiv2025

Systematic effect induced by misalignment in a Reflective Polarization Modulator for CMB, and application to the LiteBIRD case

[Abridged] The LiteBIRD mission aims to measure the Cosmic Microwave Background (CMB) polarization with unprecedented precision, targeting the detection of primordial B modes and a precise determination of the tensor-to-scalar ratio r. A central component of LiteBIRD are the polarization modulators based on Half-Wave Plates (HWP). In this work, we investigate systematic effects caused by a small, constant misalignment between the reflective HWP's rotation axis and optical axis, which mimics a wedge-like effect. This effect can introduce HWP-synchronous pointing errors, biasing polarization measurements and generating spurious B modes. Using the LiteBIRD simulation framework, we implement this wedge-like misalignment in time-ordered data and evaluate its impact on reconstructed maps and angular power spectra. Our results show that the contamination predominantly mimics lensing B modes rather than primordial tensor modes, and its impact is reduced when increasing the number of detectors. By estimating the resulting error on the tensor-to-scalar ratio, we set constraints on the maximum allowable wedge angle to ensure systematic effects remain below mission requirements. This study emphasizes the critical importance of precise optical alignment in CMB polarization experiments. Future work will address the additional effects of time-dependent HWP wobbling and more realistic scenarios with non-ideal detector pairs.

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arXiv2024

MNTES: Modeling Nonlinearity of TES detectors for Enhanced Cosmic Microwave Background measurements with LiteBIRD

Traditional methods of converting electronic readout counts to optical power incident on Transition Edge Sensors (TES) for Cosmic Microwave Background (CMB) observations involve a linear approximation. For the upcoming LiteBIRD CMB satellite, strict nonlinearity requirements must be met to prevent contamination of the science band at 4f by the 2f signal, which arises from differential transmission or emissivity related to the half-wave plate's rotation rate fHWP. These constraints cannot be met using hardware solutions alone and therefore require a form of nonlinearity correction. We present MNTES, a novel physics-based, nonlinear calibration technique. This method leverages our physical understanding of the TES power balance equation, accounts for imperfect voltage bias by casting the bias network as its Th\'evenin equivalent, and can incorporate external information such as time-varying magnetic fields and focal plane temperature variations. The detector-specific parameters of MNTES will be measured during the ground calibration campaign prior to the LiteBIRD launch, yielding conversion functions that can take raw time-ordered data and output the reconstructed incident optical power. MNTES will allow us to achieve LiteBIRD's goal of measuring the primordial tensor fluctuation spectrum to {\delta}r < 0.001.

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arXiv2023

Probing Cosmic Inflation with the LiteBIRD Cosmic Microwave Background Polarization Survey

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$μ$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.

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