  LiteBIRD is a next-generation satellite mission to measure the polarization
of the cosmic microwave background (CMB) radiation. On large angular scales the
B-mode polarization of the CMB carries the imprint of primordial gravitational
waves, and its precise measurement would provide a powerful probe of the epoch
of inflation. The goal of LiteBIRD is to achieve a measurement of the
characterizing tensor to scalar ratio $r$ to an uncertainty of $\delta
r=0.001$. In order to achieve this goal we will employ a kilo-pixel
superconducting detector array on a cryogenically cooled sub-Kelvin focal plane
with an optical system at a temperature of 4~K. We are currently considering
two detector array options; transition edge sensor (TES) bolometers and
microwave kinetic inductance detectors (MKID). In this paper we give an
overview of LiteBIRD and describe a TES-based polarimeter designed to achieve
the target sensitivity of 2~$\mu$K$\cdot$arcmin over the frequency range 50 to
320~GHz.
