  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.
