A Cryogenic Cosmic Microwave Background Polarimeter at L2 Designed Around the Large-Angle Anomalies of a Bounced Sky

This paper presents a space mission design, computed from stated assumptions and not measured, built to measure one quantity: the tensor-to-scalar ratio used as the design reference signal, for which the design case adopts 4.00e-03 in tensor-to-scalar ratio r. The instrument is a 1.5-metre off-axis telescope feeding 4,800 transition-edge bolometers cooled to 0.1 kelvin behind a continuously rotating half-wave plate, scanning the full sky in four frequency bands between 90 and 280 gigahertz from a halo orbit. It operates from a halo orbit about the Sun-Earth L2 point for 3 years. The one-day measurement uncertainty is 1.20e-03 in r; averaged over the full mission of 1096 days it falls to 3.63e-05 in r, giving a signal-to-noise ratio of 110 for the design case and a five-sigma detection limit of 1.81e-04 in r. The spacecraft has a dry mass of 1600 kilograms, a wet mass of 1810 kilograms including propellant, and a total electrical load of 2288 watts supplied by a solar array of 6.73 square metres at the operating distance. Every performance figure in this paper comes from the deposited computation; the design is simulated, not measured, and no hardware described here has been built or flown.