The Earth 2.0 (ET) space mission has entered its phase B study in China. It seeks to understand how frequently habitable Earth-like planets orbit solar-type stars (Earth 2.0s), the formation and evolution of terrestrial-like planets, and the origin of free-floating planets. The final design of ET includes six 28 cm diameter transit telescope systems, each with a field of view of 550 square degrees, and one 35 cm diameter microlensing telescope with a field of view of 4 square degrees. In transit mode, ET will continuously monitor over 2 million FGKM dwarfs in the original Kepler field and its neighboring fields for four years. Simultaneously, in microlensing mode, it will observe over 30 million I < 20.5 stars in the Galactic bulge direction. Simulations indicate that ET mission could identify approximately 40,000 new planets, including about 4,000 terrestrial-like planets across a wide range of orbital periods and in the interstellar space, ~1000 microlensing planets, ~10 Earth 2.0s and around 25 free-floating Earth mass planets. Coordinated observations with ground-based KMTNet telescopes will enable the measurement of masses for ~300 microlensing planets, helping determine the mass distribution functions of free-floating planets and cold planets. ET will operate from the Earth-Sun L2 halo orbit with a designed lifetime exceeding 4 years. The phase B study involves detailed design and engineering development of the transit and microlensing telescopes. Updates on this mission study are reported.
A space mission called “Earth 2.0 (ET)” is being developed in China to address a few of fundamental questions in the exoplanet field: How frequently habitable Earth-like planets orbit solar type stars (Earth 2.0s)? How do terrestrial planets form and evolve? Where did floating planets come from? ET consists of six 30 cm diameter transit telescope systems with each field of view of 500 square degrees and one 35 cm diameter microlensing telescope with a field of view of 4 square degrees. The ET transit mode will monitor ~1.2M FGKM dwarfs in the original Kepler field and its neighboring fields continuously for four years while the microlensing mode monitors over 30M I< 20.6 stars in the Galactic bulge direction. ET will merge its photometry data with that from Kepler to increase the time baseline to 8 years. This enhances the transit signal-to-noise ratio, reduce false positives, and greatly increases the chance to discover Earth 2.0s. Simulations show that ET transit telescopes will be able to identify ~17 Earth 2.0s, about 4,900 Earth-sized terrestrial planets and about 29,000 new planets. In addition, ET will detect about 2,000 transit-timingvariation (TTV) planets and 700 of them will have mass and eccentricity measurements. The ET microlensing telescope will be able to identify over 1,000 microlensing planets. With simultaneous observations with the ground-based KMTNet telescopes, ET will be able to measure masses of over 300 microlensing planets and determine the mass distribution functions of free-floating planets and cold planets. ET will be operated at the Earth-Sun L2 orbit with a designed lifetime longer than 4 years.
The Earth 2.0 (ET) mission is a space mission in China which will be operated at the Earth-Sun L2 orbit with a designed lifetime longer than 4 years. ET’s scientific payload consist of six 30cm diameter transit telescopes with each field of view of 500 square degrees and one 35 cm diameter microlensing telescope with a field of view of 4 square degrees. Each telescope is equipped with a camera with 2×2 9K×9K CMOS detectors, and Front-end Electronics (FEE). Each transit telescope is an f/1.57 eightlens refractive optical system while the microlensing telescope is an f/17.2 catadioptric optical system with diffraction-limited design. The diameter of 90% Encircled Energy (EE90) for transit telescopes is within 5×5 pixels while the FWHM of PSF for the microlensing telescope is less than 0.78 arcsec. Fine Guidance Sensors are mounted at the four edges of the CMOS camera. All seven telescopes are fixed on a common mounting reference plate, and a large sun shield is used to block the heat flow from the Sun and provide a stable thermal environment for the telescopes. It also blocks straylight form the Sun, Earth, and the Moon. Each telescope has an additional top hood to block straylight incident at a large angle while the top hood is also used as a radiator to cool the detectors to below - 40°C. With PID heating loops, each telescope will work at -30±0.3°C while the detectors work at - 40±0.1°C. Details of the conceptual design for the scientific payload will be presented.
The Earth 2.0 (ET) mission is a Chinese space mission to detect thousands of Earth-sized terrestrial planets, including habitable Earth-like planets orbiting solar type stars (Earth 2.0s), cold low-mass planets, and free-floating planets. The six 30 cm diameter transit telescopes will be equipped with a CMOS camera which consists of 4(2×2)9K×9K CMOS sensors. A prototype camera with a 8900×9120 pixel GSENSE 1081 BSI type CMOS sensor and temperature control is designed and developed for high precision photometry measurements. In this paper, details of this camera design and performance test results are reported.
The Earth 2.0 (ET) mission is a Chinese space mission designed to detect thousands of terrestrial-like planets, including habitable Earth-like planets orbiting solar type stars (i.e., Earth 2.0s), cold low-mass planets, and free-floating planets. Six 30cm telescopes are used for very high precision photometry measurements to detect transiting planets. In order to reach very high precision photometry, an intra-pixel response function (IPRF) of detectors needs to be measured for the ET design to keep image motions caused by spacecraft operation within an acceptable level. To characterize detectors, two setups have been developed in the lab to measure spot size of the characterization beam and subpixel sensitivity. Early characterization results are reported.
Earth 2.0 is a Chinese space satellite mission that uses the transit and microlensing methods to search for exoplanets, especially Earth-sized terrestrial planets, including habitable terrestrial planets around sun-like stars. The satellite will work in the halo orbit of the Sun-Earth L2 point for at least 4 years, and is expected to find about 20 Earth like planets in the 4-year observation period. In this paper a CCD camera prototype based on a 4kx4k CCD250 detector for early technology demonstration and high-accuracy photometric performance verification is introduced. The key performance indicators such as readout noise, gain, and linearity of the camera are tested, and the test results will be described.
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