On the sequence of deformable mirrors in MCAO: findings from an on-sky, closed-loop experiment

We performed an on-sky MCAO experiment using 4 deformable mirrors (DMs) to analyze the relevance of their sequence to the residual wavefront error. Two DMs were conjugate to 4 and 8 km. The other two DMs were placed in pupil images upstream and downstream of the 4-km and 8-km mirrors. At any time, both high altitude DMs were active but only one pupil DM was active while the other one stayed flat. Firstly, we found that the MCAO control loops using either pupil DM were stable and robust. Dynamic misregistration, which was present for the first pupil DM, was not an immediate problem for the controller. We did not notice an apparent difference when repeatedly switching between the pupil DMs during the operation. A closer analysis of the contrast in the corrected images and AO telemetry indicates an advantage when the pupil correction was applied with the DM that was downstream of the high-altitude DMs. This finding is consistent in several data recorded at different days. The difference, however, is small. A more detailed analysis is probably needed to rule out error sources potentially not considered herein to draw a final conclusion on the optimal sequence of DMs in MCAO and its practical relevance.

[1]  Steve Hegwer,et al.  Progress with solar multi-conjugate adaptive optics at NSO , 2006, SPIE Astronomical Telescopes + Instrumentation.

[2]  Roberto Ragazzoni,et al.  Commissioning multi-conjugate adaptive optics with LINC-NIRVANA on LBT , 2018, Astronomical Telescopes + Instrumentation.

[3]  Carlos Correia,et al.  Object-oriented Matlab adaptive optics toolbox , 2014, Astronomical Telescopes and Instrumentation.

[4]  Friedrich Wöger,et al.  Progress in multi-conjugate adaptive optics at Big Bear Solar Observatory , 2016, Astronomical Telescopes + Instrumentation.

[5]  Thomas Berkefeld,et al.  Latest achievements of the MCAO testbed for the GREGOR Solar Telescope , 2010, Astronomical Telescopes + Instrumentation.

[6]  Thomas Rimmele,et al.  The multi-conjugate adaptive optics system of the New Solar Telescope at Big Bear Solar Observatory , 2014, Astronomical Telescopes and Instrumentation.

[7]  Thomas Berkefeld,et al.  The 2012 status of the MCAO testbed for the GREGOR solar telescope , 2012, Other Conferences.

[8]  Thomas Berkefeld,et al.  Adaptive optics development at the German solar telescopes , 2010 .

[9]  Lianqi Wang,et al.  Fast End-to-End Multi-Conjugate AO Simulations Using Graphical Processing Units and the MAOS Simulation Code , 2012 .

[10]  Thomas Berkefeld,et al.  GREGOR MCAO looking at the Sun , 2014, Astronomical Telescopes and Instrumentation.

[11]  K. Richards,et al.  Solar multiconjugate adaptive optics at the Dunn Solar Telescope , 2010, Astronomical Telescopes + Instrumentation.

[12]  Francois Rigaut,et al.  Simulating Astronomical Adaptive Optics Systems Using Yao , 2013 .

[13]  Oskar von der Lühe Photometric stability of multiconjugate adaptive optics , 2004 .

[14]  Sylvain Oberti,et al.  Adaptive optics simulations for the European Extremely Large Telescope , 2006, Astronomical Telescopes + Instrumentation.

[15]  Marcel Carbillet,et al.  The CAOS Problem-Solving Environment: tools for AO numerical modeling and post-AO deconvolution , 2017 .

[16]  Marcos A. van Dam,et al.  Overcoming the effect of pupil distortion in multiconjugate adaptive optics , 2020, Astronomical Telescopes + Instrumentation.

[17]  Charles P. Cavedoni,et al.  Gemini multiconjugate adaptive optics system review - I. Design, trade-offs and integration , 2013, 1310.6199.

[18]  Jacques M. Beckers,et al.  Increasing the size of the isoplanatic patch with multiconjugate adaptive optics. , 1988 .

[19]  A. Sevin,et al.  Real-time end-to-end AO simulations at ELT scale on multiple GPUs with the COMPASS platform , 2018, Astronomical Telescopes + Instrumentation.

[20]  Robert H. Dicke,et al.  Phase-contrast detection of telescope seeing errors and their correction. , 1975 .

[21]  M. Sarazin,et al.  The ESO differential image motion monitor , 1990 .

[22]  Thomas Berkefeld,et al.  Results of the multi-conjugate adaptive optics system at the German solar telescope, Tenerife , 2005, SPIE Optics + Photonics.

[23]  R C Flicker Sequence of phase correction in multiconjugate adaptive optics. , 2001, Optics letters.

[24]  Bernard Delabre,et al.  On-sky Testing of the Multi-Conjugate Adaptive Optics Demonstrator , 2007 .

[25]  Alastair G. Basden,et al.  The Durham Adaptive Optics Simulation Platform (DASP): Current status , 2018, SoftwareX.

[26]  James Osborn,et al.  Deformable Mirror configuration in MCAO: is propagation a fundamental limit on visible wavelength correction? , 2017 .

[27]  Andrew P. Reeves Soapy: an adaptive optics simulation written purely in Python for rapid concept development , 2016, Astronomical Telescopes + Instrumentation.

[28]  Lei Zhu,et al.  Preliminary result of the solar multi-conjugate adaptive optics for 1m new vacuum solar telescope , 2016, Astronomical Telescopes + Instrumentation.

[29]  Francois Rigaut,et al.  Clear widens the field for observations of the Sun with multi-conjugate adaptive optics , 2017 .

[30]  J. Hardy,et al.  Adaptive Optics for Astronomical Telescopes , 1998 .

[31]  Sarah J. Diggs,et al.  Gemini multiconjugate adaptive optics system review – II. Commissioning, operation and overall performance , 2014, 1402.6906.