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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The Giant Magellan Telescope (GMT) design consists of seven circular 8.4-mdiameter mirror segments that are separated by large > 30 cm gaps, creating thepossibility of fluctuations in optical path differences due to flexure, segmentvibrations, wind buffeting, temperature effects, and atmospheric seeing. Inorder to utilize the full diffraction-limited aperture of the GMT for naturalguide star adaptive optics (NGSAO) science, the seven mirror segments must beco-phased to well within a fraction of a wavelength. The current design of theGMT involves seven adaptive secondary mirrors, an off-axis dispersed fringesensor (part of the AGWS), and a pyramid wavefront sensor (PyWFS; part of theNGWS) to measure and correct the total path length between segment pairs, butthese methods have yet to be tested "end-to-end" in a lab environment. Wepresent the design and working prototype of a "GMT High-Contrast AdaptiveOptics phasing Testbed" (p-HCAT) which leverages the existing MagAO-X AOinstrument to demonstrate segment phase sensing and simultaneous AO-control forGMT NGSAO science. We present the first test results of closed-loop pistoncontrol with one GMT segment using MagAO-X's PyWFS and a novel HolographicDispersed Fringe Sensor (HDFS) with and without simulated atmosphericturbulence. We show that the PyWFS alone was unsuccessful at controllingsegment piston with generated ~ 0.6 arcsec and ~ 1.2 arcsec seeing turbulencedue to non-linear modal cross-talk and poor pixel sampling of the segment gapson the PyWFS detector. We report the success of an alternate solution tocontrol piston using the novel HDFS while controlling all other modes with thePyWFS purely as a slope sensor (piston mode removed). This "second channel" WFSmethod worked well to control piston to within 50 nm RMS and $\pm$ 10 $\mu$mdynamic range under simulated 0.6 arcsec atmospheric seeing conditions.

The Giant Magellan Telescope high contrast adaptive optics phasing  testbed (p-HCAT): lab tests of segment/petal phasing with a pyramid wavefront  sensor and a holographic dispersed fringe sensor (HDFS) in turbulence