Abstract
We will shortly complete the testing of a cryogenic (1.8K) total-power sky monitor which will measure the temporal fluctuations of the sky brightness at millimeter wavelengths. In this article we outline the development of a polarizing Fourier Transform Spectrometer (FTS) that can characterize the spectral response of our mm-wavelength filters and entire optical system. Since the FTS will be portable, we can also measure the seasonal changes in the atmospheric transmission windows above Sierra Negra (the GTM site). These data will influence the design of submillimeter and millimeter filters for future GTM instruments.
