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avril 2019
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Roser Juanola-Parramon (NASA Goddard / UMBC) - Detecting exoplanets with the next generation of space telescopes : a technical perspective

Vendredi 5 avril 11:00-12:00

Direct imaging of exoplanets in their habitable zone is extremely challenging due to two main factors : the proximity of the planet to the parent star and the flux ratio between the planet and the parent star, usually to the order of 10^-10 in the visible. In January 2016, NASA commissioned four Mission Concept Studies for the next Decadal Survey, which will decide which kind of mission will follow the steps of extremely successful telescopes like Hubble, and the future JWST and WFIRST. Of these four studies, two of them have as a primary scientific goal to detect and characterize exoplanets in their habitable zone.
These two missions are the Large UV-Optical-Infrared (LUVOIR) Surveyor and the Habitable exoplanet Imaging Mission (HabEx), which require large apertures and coronagraphs with active wavefront control to be able to suppress the starlight so faint planets can be detected and characterized adjacent to their parent star. The Extreme Coronagraph for Living Planet Systems (ECLIPS) is the coronagraph instrument on the LUVOIR Surveyor mission concept. It is split into three channels : UV (200 to 400 nm), optical (400 nm to 850 nm), and NIR (850 nm to 2.0 microns), with each channel equipped with two deformable mirrors for wavefront control, a suite of coronagraph masks, a low-order/out-of-band wavefront sensor, and separate science imagers and spectrographs.
The Apodized Pupil Lyot Coronagraph (APLC) is one of the baselined mask technologies to enable 10^-10 contrast observations in the habitable zones of nearby stars. The LUVOIR concept uses a large, segmented primary mirror (8- 15 meters in diameter) to meet its scientific objectives. For such an observatory architecture, the coronagraph performance depends on active wavefront sensing and control and metrology subsystems to compensate for errors in segment alignment (piston and tip/tilt), secondary mirror alignment, and global low-order wavefront errors. For the LUVOIR-A architecture (15m obscured telescope), we evaluate the sensitivity to segment-to-segment tip/tilt, piston, power (focus), astigmatism, coma, trefoil and spherical errors, and to errors induced by misalignment of the secondary mirror. I will present the latest results of the simulation of these effects and discuss the achieved contrast for exoplanet detection and characterisation under these circumstances.

Peter Capack (Caltech) - TBD

Vendredi 26 avril 11:00-12:00

TBD

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