The optical design of the LiteBIRD Middle and High Frequency Telescope

TL;DR

This paper details the optical design, modeling, and characterization of the LiteBIRD Middle and High Frequency Telescope, crucial for precise polarization measurements of the Cosmic Microwave Background to detect primordial gravitational waves.

Contribution

It presents the optical design process, challenges, and current development status of the MHFT for the LiteBIRD mission, emphasizing system optimization and performance validation.

Findings

Optical modeling captures physical effects affecting performance.

Design drivers and system optimization strategies are identified.

Current development status and validation plans are outlined.

Abstract

LiteBIRD is a JAXA strategic L-class mission devoted to the measurement of polarization of the Cosmic Microwave Background, searching for the signature of primordial gravitational waves in the B-modes pattern of the polarization. The onboard instrumentation includes a Middle and High Frequency Telescope (MHFT), based on a pair of cryogenically cooled refractive telescopes covering, respectively, the 89-224 GHz and the 166-448 GHz bands. Given the high target sensitivity and the careful systematics control needed to achieve the scientific goals of the mission, optical modeling and characterization are performed with the aim to capture most of the physical effects potentially affecting the real performance of the two refractors. We describe the main features of the MHFT, its design drivers and the major challenges in system optimization and characterization. We provide the current status of the development of the optical system and we describe the current plan of activities related to optical performance simulation and validation.