Abstract: The Primordial Ination Explorer (PIXIE) uses a nulling Fourier Transform Spectrometer to measure the absoluteintensity and linear polarization of the cosmic microwave background and diuse astrophysical foregrounds.PIXIE will search for the signature of primordial ination and will characterize distortions from a blackbodyspectrum, both to precision of a few parts per billion. Rigorous control of potential instrumental eects isrequired to take advantage of the raw sensitivity. PIXIE employs a h…