First light adaptive optics systems and components for the Thirty Meter Telescope

Abstract

Adaptive optics (AO) is essential for many elements of the science case for the Thirty Meter Telescope (TMT). The initial requirements for the observatory's facility AO system include diffraction-limited performance in the near IR, with 50 per cent sky coverage at the galactic pole. Point spread function uniformity and stability over a 30 arc sec field-ofview are also required for precision photometry and astrometry. These capabilities will be achieved via an order 60x60 multi-conjugate AO system (NFIRAOS) with two deformable mirrors, six laser guide star wavefront sensors, and three low-order, IR, natural guide star wavefront sensors within each client instrument. The associated laser guide star facility (LGSF) will employ 150W of laser power at a wavelength of 589 nm to generate the six laser guide stars.We provide an update on the progress in designing, modeling, and validating these systems and their components over the last two years. This includes work on the layouts and detailed designs of NFIRAOS and the LGSF; fabrication and test of a full-scale prototype tip/tilt stage (TTS); Conceptual Designs Studies for the real time controller (RTC) hardware and algorithms; fabrication and test of the detectors for the laser-and natural-guide star wavefront sensors; AO system modeling and performance optimization; lab tests of wavefront sensing algorithms for use with elongated laser guide stars; and high resolution LIDAR measurements of the mesospheric sodium layer. Further details may be found in specific papers on each of these topics.

Real-time turbulence profiling with a pair of laser guide star Shack–Hartmann wavefront sensors for wide-field adaptive optics systems on large to extremely large telescopes

“…Detailed Monte Carlo simulations were conducted in order to test the accuracy of the proposed method in the context of the TMT MCAO system [1], which is an order 60 ϫ 60 wavefront sensing and order 63ϫ 63 correction on the ground conjugated deformable mirror (DM) and order 76ϫ 76 correction on the h DM = 11.2 km conjugated DM. Our study has been performed for high-resolution simulated turbulence profiles obtained from generalized scintillation detection and ranging (SCIDAR) measurements over Mauna Kea during four nights in 2002 [20].…”

“…(3) to form a 6-layer estimate. The chosen values of correspond to two possible LGS pairs from the TMT 70Љ diameter 6-LGS asterism (pentagon+ on-axis) [1]. The resulting 27 influence functions are displayed in Fig.…”

“…Many systems will utilize multiple mesospheric sodium LGSs in order to implement laser tomography for ground-layer adaptive optics (GLAO), laser tomography adaptive optics (LTAO), multiobject adaptive optics (MOAO) or multi-conjugate adaptive optics (MCAO) [1][2][3][4][5]. Real-time turbulence profiling is necessary for these wide-field AO systems to tune their tomographic wavefront reconstruction algorithm [6,7] and perform a variety of image post-processing tasks involving point-spread function reconstruction [8].…”

Tip/tilt point spread function reconstruction for laser guide star multi-conjugate adaptive optics

“…In order to enable such science programs, AO systems on existing telescopes and future extremely large telescopes are required to meet tight photometry and ast rometry budgets. For instance, the multi conjugate adaptive optics (MCAO) system under de sign for the Thirty Meter Telescope (TMT) is required to provide 2% differential photometry over a 30'' field of view (FoV) for a 10 min integration at a wavelength of 1 micron, and 50 microarcsec root-mean-square (RMS) time dependent differential astrometry over the same FoV for a 100 sec integration in H band [7,8].…”

Simulation model based approach for long exposure atmospheric point spread function reconstruction for laser guide star multiconjugate adaptive optics

“…In order to enable these science programs, AO systems on existing and future extremely large telescopes are required to meet tight photometry and astrometry budgets. For instance, the laser guide star (LGS) multiconjugate adaptive optics (MCAO) system, under design for the Thirty Meter Telescope (TMT), is required to provide 2% differential photometry (relative brightness between two point sources) over a 30 arcsec diameter field of view (FoV) for a 10 min integration at a wavelength of 1 μm, and 50 microarcsec root-meansquare (RMS) time dependent differential astrometry (relative separation between two point sources) over the same FoV for a 100 s integration in H band [6,7].…”