Space payload

Concept

• The payload design follows that of the prototype but with three frequencies (90, 150, and 270 GHz). The first two (90 and 150 GHz) are optimal for observing the CMB from the ground, and the third (270 GHz) is optimal for observing interstellar dust emission. A drawing of the instrument is shown in the figure 

• The COSMOCal source is 100% polarized. The two addtional requirements that determine the design of the payload are the accuracy of the polarization angle and the flux received on Earth. 

• The angle must be known with respect to the celestial reference frame to an accuracy of 0.1° (3σ). The flux received on Earth must be comparable to that of the astronomical sources used today to calibrate microwave instruments. 

• At 90 and 150 GHz, the user requirement is that the flux from the COSMOCal source be comparable to that of Uranus in total intensity. At 270 GHz, the requirement is that the COSMOCal flux be comparable to that of the Crab Nebula in polarization.