GRAVITY Coudé Infrared Adaptive Optics (CIAO) system for the VLT Interferometer

摘要

GRAVITY is a second generation instrument for the VLT Interferometer, designed to enhance the near-infraredastrometric and spectro-imaging capabilities of VLTI. Combining beams from four telescopes, GRAVITY willprovide an astrometric precision of order 10 micro-arcseconds, imaging resolution of 4 milli-arcseconds, and lowand medium resolution spectro-interferometry, pushing its performance far beyond current infrared interferometriccapabilities. To maximise the performance of GRAVITY, adaptive optics correction will be implementedat each of the VLT Unit Telescopes to correct for the e_ects of atmospheric turbulence. To achieve this, theGRAVITY project includes a development programme for four new wavefront sensors (WFS) and NIR-optimizedreal time control system. These devices will enable closed-loop adaptive correction at the four Unit Telescopesin the range 1.4-2.4 μm. This is crucially important for an e_cient adaptive optics implementation in regionswhere optically bright references sources are scarce, such as the Galactic Centre. We present here the design ofthe GRAVITY wavefront sensors and give an overview of the expected adaptive optics performance under typicalobserving conditions. Bene_ting from newly developed SELEX/ESO SAPHIRA electron avalanche photodiode(eAPD) detectors providing fast readout with low noise in the near-infrared, the AO systems are expected toachieve residual wavefront errors of 400 nm at an operating frequency of 500 Hz.≤© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.