LiteBIRD is a candidate for JAXA’s strategic large mission to observe the cosmic microwave background (CMB) polarization over the full sky at large angular scales. It is planned to be launched in the 2020s with an H3 launch vehicle for three years of observations at a Sun-Earth Lagrangian point (L2). The concept design has been studied by researchers from Japan, U.S., Canada and Europe during the ISAS Phase-A1. Large scale measurements of the CMB B-mode polarization are known as the best probe to detect primordial gravitational waves. The goal of LiteBIRD is to measure the tensor-to-scalar ratio (r) with precision of r < 0:001. A 3-year full sky survey will be carried out with a low frequency (34 - 161 GHz) telescope (LFT) and a high frequency (89 - 448 GHz) telescope (HFT), which achieve a sensitivity of 2.5 μK-arcmin with an angular resolution 30 arcminutes around 100 GHz. The concept design of LiteBIRD system, payload module (PLM), cryo-structure, LFT and verification plan is described in this paper.
In this paper we discuss the latest developments of the STRIP instrument of the “Large Scale Polarization Explorer” (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the “B-modes” of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the “Observatorio del Teide” in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization.
We present a preliminary study of the sky scanning strategy for the LSPE-STRIP instrument, a ground-based telescope that will be installed at the Teide Observatory (Tenerife, Canary Islands) in early 2019 and will observe the polarized emission of about 25% of the sky in the Northern Hemisphere at 43 and 95 GHz. The same sky portion will be observed at 140, 220 and 240 GHz by LSPE-SWIPE, a stratospheric balloon scheduled for a long-duration flight around the North Pole during the Arctic winter of 2019/2020. The combination of data from the two instruments aims at constraining the tensor-to-scalar ratio down to r ~ 0.03. In our paper we discuss the main scanning strategy requirements (overlap with SWIPE coverage, sensitivity distribution, observation of calibration sources) and show how we obtain a trade-off by spinning the telescope around the azimuth axis with constant elevation and angular velocity. The combination of the telescope motion with the Earth rotation will guarantee the access to the large angular scales. We will observe periodically the Crab Nebula as well as the Perseus molecular cloud. The Crab is one of the best known polarized sources in the sky and it will be observed for calibration purposes. The second one is a source of Anomalous Microwave Emission that could be characterized both in intensity and polarization.