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Register a new userPALM-3000: Exoplanet Adaptive Optics for the 5-meter Hale Telescope
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We describe and report first results from PALM-3000, the second-generation astronomical adaptive optics facility for the 5.1-m Hale telescope at Palomar Observatory. PALM-3000 has been engineered for high-contrast imaging and emission spectroscopy of brown dwarfs and large planetary mass bodies at near-infrared wavelengths around bright stars, but also supports general natural guide star use to V ~ 17. Using its unique 66 x 66 actuator deformable mirror, PALM-3000 has thus far demonstrated residual wavefront errors of 141 nm RMS under 1 arcsecond seeing conditions. PALM-3000 can provide phase conjugation correction over a 6.4 x 6.4 arcsecond working region at an observing wavelength of 2.2 microns, or full electric field (amplitude and phase) correction over approximately one half of this field. With optimized back-end instrumentation, PALM-3000 is designed to enable as high as 10e-7 contrast at ~1 arc second angular separation, after including post-observation speckle suppression processing. While optimization of the adaptive optics system is ongoing, we have already successfully commissioned five back-end science instruments and begun a major exoplanet characterization survey, Project 1640, with our partners at American Museum of Natural History and Jet Propulsion Laboratory.
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We present a multi-conjugate adaptive optics (MCAO) system simulator bench, HeNOS (Herzberg NFIRAOS Optical Simulator). HeNOS is developed to validate the performance of the MCAO system for the Thirty Meter Telescope, as well as to demonstrate techniques critical for future AO developments. In this paper, we focus on describing the derivations of parameters that scale the 30-m telescope AO system down to a bench experiment and explain how these parameters are practically implemented on an optical bench. While referring other papers for details of AO technique developments using HeNOS, we introduce the functionality of HeNOS, in particular, three different single-conjugate AO modes that HeNOS currently offers: a laser guide star AO with a Shack-Hartmann wavefront sensor, a natural guide star AO with a pyramid wavefront sensor, and a laser guide star AO with a sodium spot elongation on the Shack-Hartmann corrected by a truth wavefront sensing on a natural guide star. Laser tomography AO and ultimate MCAO are being prepared to be implemented in the near future.
PALM-3000 (P3K), the second generation adaptive optics (AO) instrument for the 5.1 meter Hale telescope at Palomar Observatory, was released as a facility class instrument in October 2011 and has since been used on-sky for over 600 nights as a workhorse science instrument and testbed for coronagraph and detector development. In late 2019 P3K underwent a significant upgrade to its wavefront sensor (WFS) arm and real-time control (RTC) system to reinforce its position as a state-of-the-art AO facility and extend its faint-end capability for high-resolution imaging and precision radial velocity follow-up of Kepler and TESS targets. The main features of this upgrade include an EM-CCD WFS camera capable of 3.5 kHz framerates, and an advanced Digital signal Processor (DSP) based RTC system to replace the aging GPU based system. Similar to the pre-upgrade system, the Shack-Hartmann wavefront sensor supports multiple pupil sampling modes using a motorized lenslet stage. The default sampling mode with 64x64 subapertures has been re-commissioned on-sky in late 2019, with a successful return to science observations in November 2019. In 64x mode the upgraded system is already achieving K-band Strehl ratios up to 85% on sky and can lock on natural guide stars as faint as mV=16. A 16x16 subaperture mode is scheduled for on-sky commissioning in Fall 2020 and will extend the systems faint limit even further. Here we present the design and on-sky re-commissioning results of the upgraded system, dubbed P3K-II.
The World Space Observatory for Ultraviolet (WSO-UV) is an orbital optical telescope with a 1.7 m-diameter primary mirror currently under development. The WSO-UV is aimed to operate in the 115-310 nm UV spectral range. Its two major science instruments are UV spectrographs and a UV imaging field camera with filter wheels. The WSO-UV project is currently in the implementation phase, with a tentative launch date in 2023. Recently, two additional instruments devoted to exoplanets have been proposed for WSO-UV, which are the focus of this paper. UVSPEX, a UV-Spectrograph for Exoplanets, aims to determine atomic hydrogen and oxygen abundance in the exospheres of terrestrial exoplanets. The spectral range is 115-130 nm which enables simultaneous measurement of hydrogen and oxygen emission intensities during an exoplanet transit. Study of exosphere transit photometric curves can help differentiate among different types of rocky planets. The exospheric temperature of an Earth-like planet is much higher than that of a Venus-like planet, because of the low mixing ratio of the dominant coolant (CO2) in the upper atmosphere of the former, which causes a large difference in transit depth at the oxygen emission line. Thus, whether the terrestrial exoplanet is Earth-like, Venus-like, or other can be determined. SCEDI, a Stellar Coronagraph for Exoplanet Direct Imaging is aimed to directly detect the starlight reflected from exoplanets orbiting their parent stars or from the stellar vicinity including circumstellar discs, dust, and clumps. SCEDI will create an achromatic (optimized to 420-700 nm wavelength range), high-contrast stellocentric coronagraphic image of a circumstellar vicinity. The two instruments: UVSPEX and SCEDI, share common power and control modules. The present communication outlines the science goals of both proposed instruments and explains some of their engineering features.
Vibrations are a key source of image degradation in ground-based instrumentation, especially for high-contrast imaging instruments. Vibrations reduce the quality of the correction provided by the adaptive optics system, blurring the science image and reducing the sensitivity of most science modules. We studied vibrations using the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument at the Subaru Telescope as it is the most vibration sensitive system installed on the telescope. We observed vibrations for all targets, usually at low frequency, below 10 Hz. Using accelerometers on the telescope, we confirmed that these vibrations were introduced by the telescope itself, and not the instrument. It was determined that they were related to the pitch of the encoders of the telescope drive system, both in altitude and azimuth, with frequencies evolving proportionally to the rotational speed of the telescope. Another strong vibration was found in the altitude axis of the telescope, around the time of transit of the target, when the altitude rotation speed is below 0.12 arcsec/s. These vibrations are amplified by the 10-Hz control loop of the telescope, especially in a region between 4 and 6 Hz. In this work, we demonstrate an accurate characterization of the frequencies of the telescope vibrations using only the coordinates -right ascension and declination- of the target, and provide a means by which we can predict them for any telescope pointing. This will be a powerful tool that can be used by more advanced wavefront control algorithms, especially predictive control, that uses informations about the disturbance to calculate the best correction.
AOLI (Adaptive Optics Lucky Imager) is a state-of-art instrument that combines adaptive optics (AO) and lucky imaging (LI) with the objective of obtaining diffraction limited images in visible wavelength at mid- and big-size ground-based telescopes. The key innovation of AOLI is the development and use of the new TP3-WFS (Two Pupil Plane Positions Wavefront Sensor). The TP3-WFS, working in visible band, represents an advance over classical wavefront sensors such as the Shack-Hartmann WFS (SH-WFS) because it can theoretically use fainter natural reference stars, which would ultimately provide better sky coverages to AO instruments using this newer sensor. This paper describes the software, algorithms and procedures that enabled AOLI to become the first astronomical instrument performing real-time adaptive optics corrections in a telescope with this new type of WFS, including the first control-related results at the William Herschel Telescope (WHT).
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