From Event: SPIE Optical Engineering + Applications, 2017
The Theia mission, as a natural successor to Gaia, will be the first extremely-high-precision astrometric surveyor that may emerge from the last ESA M5 call in October 2016. A major objective of Theia in the context of this conference is the detection by astrometry of Earths and Super-Earths exoplanets in the habitable zone of nearby A to M stars. This can be done by astrometry from space if a motion of <1-microarcesec can be recorded (0.3 microarcsec for an Earth/Sun system at 10 pc). Such an accuracy can be reached by Theia in the form of an 0.8-m telescope with 0.5° FOV in orbit at L2 for 3,5 years and providing repeated differential astrometric measurements between the science target and background reference stars. The exoplanet program will use circa 10% of the mission lifetime and will be able to survey 63 nearby stars with a ~0.6 microarssec astrometric floor to eventually detect planets down to 0.2 M_earth over circa 50 visits. In order to measure a centroid position on the CCD with an accuracy of 1e-5 pixels, Theia’s high-precision measurement relies on an on-board interferometric laser metrology unit to calibrate out the pixel’s offset to the nominal position, as well as the inter- and intra-pixel quantum efficiency. The preliminary Theia mission assessment allowed us to identify a safe and robust mission architecture that demonstrates the mission feasibility within the Soyuz ST launch envelope and a small M-class mission cost cap. We present here these features and the corresponding exoplanet program.
Lucas Labadie, Fabien Malbet, Alain Léger, Céline Boehm, Antoine Crouzier, and Alberto Krone-Martins, "The exoplanet program of the microarcsecond astrometric observatory Theia (Conference Presentation)," Proc. SPIE 10400, Techniques and Instrumentation for Detection of Exoplanets VIII, 104001F (Presented at SPIE Optical Engineering + Applications: August 10, 2017; Published: 19 September 2017); https://doi.org/10.1117/12.2273619.5581292806001.
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