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.
With a focus on off-the-shelf components, Twinkle is the first in a series of cost competitive small satellites managed and financed by Blue Skies Space Ltd. The satellite is based on a high-heritage Airbus platform that will carry a 0.45 m telescope and a spectrometer which will provide simultaneous wavelength coverage from 0.5–4.5 μm. The spacecraft prime is Airbus Stevenage while the telescope is being developed by Airbus Toulouse and the spectrometer by ABB Canada. Scheduled to begin scientific operations in 2025, Twinkle will sit in a thermally-stable, sun-synchronous, low-Earth orbit. The mission has a designed operation lifetime of at least seven years and, during the first three years of operation, will conduct two large-scale survey programmes: one focused on Solar System objects and the other dedicated to extrasolar targets. Here we present an overview of the architecture of the mission, refinements in the design approach, and some of the key science themes of the extrasolar survey.
Lijiang Exoplanet Tracker (LijET) was designed to detect exoplanets with extremely high precision radial velocity (RV) measurements, and it was mounted on 2.4m telescope at Lijiang Observatory in 2011. The Dispersed Fixed- Delay Interferometry (DFDI) mode of LiJET is a combination of a thermally compensated monolithic michelson interferometer and a cross-dispersed echelle spectrograph. When the slit width is 1.6”, the spectral resolution is 18000. With a 4k x 4k CCD, the spectrograph has wavelength coverage of 390nm-690nm. The temperature stability of the instrument is 25±0.001°C, and the pressure stability of the instrument is 10.9±0.001psi. LiJET realize high precision RV measurements by measuring the phase shifts of fringes in the slit direction. Differential RV is a function of light speed, phase shift, wavelength and optical delay. Thus, optical delay is necessary to be determined accurately to take differential RV measurements to derive precise RV. We used thorium argon (ThAr) and tungsten lamp to calibration the DFDI spectrum of LiJET, and then to calculate the optical delay at different channels on the CCD detector.
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