COBRAS-SAMBA

COBRAS/SAMBA has been selected by ESA as the next Medium-sized Mission. Following COBE which gave the first evidence for primordial fluctuations in the Cosmic Microwave Background (CMB) at angular scales larger than 7 degrees, it aims at imaging the CMB over the whole sky with a sensitivity Delta T/T of 2 x 10(-6) and an angular resolution of 10 arcminutes. To achieve this objective, the sky will be mapped in nine frequency channels ranging between 30 and 900 GHz, with a sensitivity and angular resolution which allow the separation of the cosmological signal from other sources of confusion. The telescope, 1 meter useful aperture, passively cooled to 100K, will be placed on an L2 sun-earth orbit. The payload includes 56 HEMT detectors at 100K for the lower frequencies (31.5, 53, 90 and 125 GHz), and 56 bolometers cooled at 0.1 K with a He-4/He-3 dilution fridge and mechanical cryocoolers for the higher frequencies (143, 217, 353, 545 and 857 GHz).