English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

High-contrast imaging will be a challenge for future ELTs, because theirvibrations create low-order aberrations - mostly tip/tilt - that reducecoronagraphic performances at 1.2 lambda/D and above. A Low-Order WaveFrontSensor (LOWFS) is essential to measure and control those aberrations. Anexperiment simulating a starlight suppression system is currently developed atNASA Ames Research Center, and includes a LOWFS controlling tip/tilt modes inreal-time at 500 Hz. The LOWFS allowed us to reduce the tip/tilt disturbancesto 1e-3 lambda/D rms, enhancing the previous contrast by a decade, to 8e-7between 1.2 and 2 lambda/D. A Linear Quadratic Gaussian (LQG) controller iscurrently implemented to improve even more that result by reducing residualvibrations. This testbed is developed for the mission EXCEDE (EXoplanetaryCircumstellar Environments and Disk Explorer), selected by NASA for technologydevelopment, and designed to study the formation, evolution and architecturesof exoplanetary systems and characterize circumstellar environments intostellar habitable zones. It is composed of a 0.7 m telescope equipped with aPhase-Induced Amplitude Apodization Coronagraph (PIAA-C) and a 2000-elementMEMS deformable mirror, capable of raw contrasts of 1e-6 at 1.2 lambda/D and1e-7 above 2 lambda/D. Although the testbed simulates space conditions, itsLOWFS has the same design than on the SCExAO instrument at Subaru telescope,with whom it shares the same kind of problematic. Experimental results showthat a good knowledge of the low-order disturbances is a key asset for highcontrast imaging, whether for real-time control or for post processing, both inspace and on ground telescopes.

Experimental study of a low-order wavefront sensor for a high-contrast coronagraphic imager at 1.2 lambda/D