LiteBIRD the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun-Earth Lagrangian point L2, where it will map the cosmic microwave background (CMB) polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of 2.2 μK-arcmin, with a typical angular resolution of 0.5○ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions and synergies with other projects. Subject Index LiteBIRD cosmic inflation, cosmic microwave background, B-mode polarization, primordial gravitational waves, quantum gravity, space telescope
This paper reports the test results and evaluation of gravity effects on long-distance loop heat pipe (LLHP) with 10 m distances for heat transport. First, the LLHP was designed based on the one-dimensional steady-state model, fabricated and tested. Test results showed the LLHP could transport heat up to 340 W for 10 m and the thermal resistance between the evaporator and the condenser was 0.12 K/W under horizontal condition. Next, the LLHP was tested in top-heat mode. The maximum heat transports were 310, 270, 220 W and the thermal resistances were 0.15, 0.17, 0.22 K/W under 30, 60, 100 cm anti-gravity condition respectively. The heat transfer efficiency of the LLHP was discussed in detail. The evaluation results showed 71.4 % of the 340 W heat load was dissipated at the condenser under the horizontal condition. On the other hand, 62.8, 61.8, 57.1 % of the maximum heat load was dissipated at the condenser under 30, 60, 100 cm anti-gravity condition respectively. The calculation model was in good agreement with the experimental results by considering the existence of a vapor pocket between the evaporator case and the vapor-liquid interface. This analysis indicated the vapor blanket generates easily and becomes thicker as anti-gravity effect increases.
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