The large scale polarization explorer (LSPE) for CMB measurements: performance forecast

Abstract

The measurement of the polarization of the Cosmic Microwave Background (CMB) radiation is one of the current frontiers in cosmology. In particular, the detection of the primordial divergence-free component of the polarization field, the B-mode, could reveal the presence of gravitational waves in the early Universe. The detection of such a component is at the moment the most promising technique to probe the inflationary theory describing the very early evolution of the Universe. We present the updated performance forecast of the Large Scale Polarization Explorer (LSPE), a program dedicated to the measurement of the CMB polarization. LSPE is composed of two instruments: LSPE-Strip, a radiometer-based telescope on the ground in Tenerife-Teide observatory, and LSPE-SWIPE (Short-Wavelength Instrument for the Polarization Explorer) a bolometer-based instrument designed to fly on a winter arctic stratospheric long-duration balloon. The program is among the few dedicated to observation of the Northern Hemisphere, while most of the international effort is focused into ground-based observation in the Southern Hemisphere. Measurements are currently scheduled in Winter 2022/23 for LSPE-SWIPE, with a flight duration up to 15 days, and in Summer 2022 with two years observations for LSPE-Strip. We describe the main features of the two instruments, identifying the most critical aspects of the design, in terms of impact on the performance forecast. We estimate the expected sensitivity of each instrument and propagate their combined observing power to the sensitivity to cosmological parameters, including the effect of scanning strategy, component separation, residual foregrounds and partial sky coverage. We also set requirements on the control of the most critical systematic effects and describe techniques to mitigate their impact. LSPE will reach a sensitivity in tensor-to-scalar ratio of σ r < 0.01, set an upper limit r < 0.015 at 95% confidence level, and improve constraints on other cosmological parameters.

Improved Constraints on Cosmic Birefringence from the WMAP and Planck Cosmic Microwave Background Polarization Data

“…To this end, both on-going and future groundbased [58][59][60][61][62][63][64][65][66], balloon-borne [67,68], and spaceborne [69,70] experiments are expected to lead to a convincing discovery (or otherwise) of cosmic birefringence. If proven to be a cosmological signal, isotropic cosmic birefringence would have a profound impact on cosmology, particle physics, and quantum gravity [71][72][73][74][75][76][77][78][79][80][81].…”

A Testbed for Modeling Validation and Characterization of Quasi-optical Elements in Microwave Receivers

“…Through these features, SWIPE is expected to achieve a final Q,U map sensitivity of 10, 17 and 34μK CMB ⋅ arcmin in its three bands, and it aims at constraining a tensor-to-scalar ratio of r=0.03 with 3 significance in conjunction with its partner ground-based instrument, LSPE/STRIP [1].…”

“…SWIPE [1,2] is a microwave polarimeter devoted to the search of such tiny curllike features in the linear polarization pattern of the CMB anisotropies, as a part of the Large Scale Polarization Explorer (LSPE) project. Given the ambitious observational target, every subsystem in the receiver must be carefully modeled and tested to assess its compliance with the tight requirements on calibration and systematics.…”

Performance forecasts for the primordial gravitational wave detection pipelines for AliCPT-1

“…At present, the tightest limits on the tensor-to-scalar ratio at a pivot scale of k ˚" 0.05 Mpc ´1 is r ă 0.036 at 95% confidence, which comes from the recent joint analysis of BICEP/Keck and Planck data [28]. Aside from these ongoing experiments, LSPE [32], QUBIC [33], Simons Observatory [34], and SPIDER [35] will be joining the measurement efforts soon. The future of CMB B-mode measurements will be lead by the LiteBIRD satellite mission [36], and the CMB-S4 ground-based observatory [37].…”