Overview of the Medium and High Frequency Telescopes of the LiteBIRD satellite mission

TL;DR

This paper provides an overview of the design and technical challenges of the Medium- and High-Frequency Telescopes of the LiteBIRD satellite, aimed at detecting primordial gravitational waves via CMB polarization measurements.

Contribution

It introduces the design details and challenges of the MHFT, including cryogenic cooling, optical components, and detector arrays, for the LiteBIRD mission.

Findings

Design of cryogenic refractive telescopes cooled to 5K

Implementation of a rotating half-wave plate as the first optical element

Deployment of over three thousand TES detectors at 100mK

Abstract

LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34GHz to 448GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium- and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89-224GHz) and the High-Frequency Telescope (166-448GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD.