| LiteBIRD | |
| Mission Type: | Space observation |
| Operator: | JAXA / ISAS |
| Mission Duration: | Planned: 3 years |
| Dry Mass: | Approx. 450 kg [1] |
| Power: | < 500 W |
| Launch Date: | 2032 (planned) |
| Launch Rocket: | H3 |
| Launch Site: | Tanegashima LA-Y2 |
| Launch Contractor: | Mitsubishi Heavy Industries |
| Telescope Diameter: | LFT: 40 cm HFT: 20 cm |
| Telescope Focal Length: | ~1,100 mm [2] |
| Trans Capacity: | 10 Gb/day |
| Programme: | Large-class Missions |
| Previous Mission: | MMX |
LiteBIRD (Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection) is a planned small space observatory that aims to detect the footprint of the primordial gravitational wave on the cosmic microwave background (CMB) in a form of polarization pattern called B-mode. LiteBIRD and OKEANOS were the two finalists for Japan's second Large-Class Mission.[3] [4] In May 2019, LiteBIRD was selected by the Japanese space agency.[5] LiteBIRD is planned to be launched in 2032 with an H3 launch vehicle for three years of observations at the Sun-Earth Lagrangian point L2.[6] [7]
Cosmological inflation is the leading theory of the first instant of the universe, called the Big Bang theory. Inflation postulates that the universe underwent a period of rapid expansion an instant after its formation, and it provides a convincing explanation for cosmological observations.[8] Inflation predicts that primordial gravitational waves were created during the inflationary era, about 10−38 second after the beginning of the universe.[9] The primordial gravitational waves are expected to be imprinted in the CMB polarization map as special patterns, called the B-mode.[9] Measurements of polarization of the CMB radiation are considered as the best probe to detect the primordial gravitational waves,[10] that could bring a profound knowledge on how the Universe began, and may open a new era of testing theoretical predictions of quantum gravity, including those by the superstring theory.[9] The science goal of LiteBIRD is to measure the CMB polarization over the entire sky with the sensitivity of δr <0.001, which allows testing the major single-field slow-roll inflation models experimentally.[1] [11] The design concept is being studied by an international team of scientists from Japan, U.S., Canada and Europe.[3] [12]
In order to separate CMB from the galactic emission, the measurements will cover 40 GHz to 400 GHz during a 3-year full sky survey using two telescopes on LiteBIRD.[8] [3] The Low Frequency Telescope (LFT) covers 40 GHz to 235 GHz, and the High Frequency Telescope (HFT) covers 280 GHz to 400 GHz. LFT has a 400 mm apertureCrossed-Dragone telescope, and HFT has a 200 mm aperture on-axis refractor with two silicon lenses.[8] [3] The baseline design considers an array of 2,622 superconducting polarimetric detectors.[8] [13] The entire optical system will be cooled down to approximately 5K to minimize the thermal emission,[14] and the focal plane is cooled to 100 mK with a two-stage sub-Kelvin cooler.[8]