SPM, A SUBMILLIMETER PHOTOMETER FOR PRONAOS

SPM is a multi-channels photometer designed to obtain the best sensiti vity at the focus of the 2 m balloon-borne PRONAOS telescope. Its scie ntific goals include the measurement of cosmological background anisot ropy, which is important for understanding the origin of the structure in the universe and the observation of cold solid matter in the inter stellar medium as an indicator of the physical conditions that prevail in star forming regions. SPM consists of warm optics that ensure beam switching and in-flight calibration, a liquid helium cryostat that co ntains filters and the He-3 cooled bolometers, and electronics for hou sekeeping and data handling. The spectral bands are 180-240 mum, 240-3 40 mum, 340-540 mum and 540-1200 mum. They are defined by dichroics, w hich allows simultaneous observations in the four bands. The expected NEDELTAT in flight is significantly less than 1 mK in all the bands. S PM will fly with PRONAOS in May 1994.