The MMT Adaptive optics exoPlanet characterization System (MAPS) is currently in its engineering phase, operating on sky at the MMT Telescope. The MAPS Adaptive Secondary Mirror’s actuators are controlled by a closed loop modified PID control law and an open loop feed forward law, which in combination allows for faster actuator response time. An essential element of achieving the secondary’s performance goals involves the process of PID gain tuning. To start, we briefly discuss the design of the MAPS ASM and its actuators. We then describe the actuator positional control system and control law. Next, we discuss a few of the issues that make ASM tuning difficult. We then outline our initial attempts at tuning the actuator controllers, and discuss the use of actuator positional power spectra for both tuning and determining the health and failure states of individual actuators. We conclude by presenting the results of our latest round of tuning configuration trials, which have been successful at decreasing mirror latency, increasing operational mirror modes and improving image PSF.
The MMT AO exoPlanet characterization System is an upgrade for the 6.5-m MMT observatory to the 20-year-old MMTAO adaptive secondary mirror (ASM) with new electronics, a new AO system with two pyramid wavefront sensors spanning the visible through infrared, and a suite of upgraded science cameras optimized for studying the atmospheres of extrasolar planets. We began on-sky engineering and commissioning in October 2022, and have progressed through first light to calibrations at this time. The AO system is complex with its dual wavefront sensors, and the ASM can only be calibrated on-sky. We will present the current status and results of commissioning the MAPS AO system.
The Little Ultraviolet Camera (LUVCamera) is a low-cost, high-performance UV/optical camera system designed to support a range of space-based astronomical facilities. At the heart of LUVCamera is a GSENSE 4040-BSI scientific CMOS (sCMOS) sensor, similar to those found in commercial-off-the-shelf (COTS) cameras. Given the intended use of LUVCamera in space-based missions, it is crucial to understand not only the performance of the sensor, but also the degradation of that performance due to effects from radiation in space environments. In this work, we report our characterization results of a SBIG Aluma AC4040 which utilizes this sensor, as well as those of a SBIG Aluma AC2020 (based on the smaller GSENSE 2020-BSI) which has been exposed to radiation. Specifically, we detail the methods used to characterize the sensors along with measurements of the read noise (RN), dark current (DC), and absolute quantum efficiency (QE). Additionally, we report changes in those quantities after radiation exposure for the AC2020. We conclude that COTS sCMOS sensors such as these are sufficiently suited for applications in space-based missions.
Great progress has been made applying deep learning methods to adaptive optics (AO) control, focus has largely been on reinforcement learning (RL) methods. While RL is a powerful tool and shows promising results, it requires continual learning while on sky to truly be effective. This makes it difficult to apply optimization techniques, such as kernel compilation, pruning, or – in the most extreme cases – hard coded networks in hardware, which may be necessary for high speed extreme AO control. We present a method and optical bench results for supervised training of AO predictive control networks trained using only simulated data. This can be accomplished by varying both the optical parameters of the AO system as well as the parameters of the simulated atmosphere; teaching the network to generalize for optical as well as atmospheric conditions. Our method also alleviates issues with both online and supervised learning methods trained on saved telemetry which may over-fit to local conditions that can vary from night to night. This training methodology is general enough to be widely applicable among most AO systems and has proven to be effective in our optical bench experiments.
With the commissioning of the refurbished adaptive secondary mirror (ASM) for the 6.5-meter MMT Observatory under way, special consideration had to be made to properly calibrate the mirror response functions to generate an interaction matrix (IM). The commissioning of the ASM is part of the MMT Adaptive optics exo- Planet characterization System (MAPS) upgrade the observatory’s legacy adaptive optics (AO) system. Unlike most AO systems, MAPS employs a convex ASM which prevents the introduction of a calibration source capable of simultaneously illuminating its ASM and wavefront sensor (WFS). This makes calibration of the AO system a significant hurdle in commissioning. To address this, we have employed a hybrid calibration strategy we call the Efficient Synthesis of Calibrations for Adaptive Optics through Pseudo-synthetic and Empirical methods (ESCAPE). ESCAPE combines the DO-CRIME on-sky calibration method with the SPRINT method for computing pseudo-synthetic calibration matrices. To monitor quasi-static system change, the ESCAPE methodology rapidly and continuously generates pseudo-synthetic calibration matrices using continual empirical feedback in either open or closed-loop. In addition, by measuring the current IM in the background while in close-loop, we are also able to measure the optical gains for pyramid wavefront sensor (PyWFS) systems. In this paper, we will provide the mathematical foundation of the ESCAPE calibration strategy and on-sky results from its application in calibrating the MMT Observatory’s ASM. Additionally, we will showcase the validation of our approach from our AO testbed and share preliminary on-sky results from MMT.
Many modern astronomical instruments rely on the optimal coupling of starlight into single-mode fibers (SMFs). For ground-based telescopes, this coupling is limited by atmospheric turbulence. We propose an integrated wavefront corrector based on silicon-on-insulator (SOI) photonics, which samples the aberrated wavefront via a microlens array (MLA). The MLA focuses the sampled wavefront onto an array of grating couplers that inject the beamlets into the single-mode waveguides of the corrector. The beams in each waveguide are then shifted in phase using thermo-optic phase shifters before combining the co-phased beams into one single-mode waveguide. In this work, we analyze the external factors that we anticipate will impact the performance of the corrector. Specifically, we study the effects of the telescope pupil function with obscuration, determine whether the corrector requires tip/tilt pre-correction, and analyze the impact of scintillation on the correction quality.
The Research, Experiment and Validation of adaptive Optics on a Legacy Telescope (REVOLT) project is an on-sky AO technology research platform which was commissioned at the Dominion Astrophysical Observatory’s (DAO) 1.2m telescope in Victoria, Canada in June 2022. The goal of the project is to provide a flexible and expandable AO system to test a wide variety of technologies and control strategies with rapid deployment to sky. To date, REVOLT has enabled the first on-sky use of the Herzberg Extensible Adaptive Realtime Toolkit (HEART), a realtime controller software package developed at the National Research Council of Canada’s Herzberg Astronomy and Astrophysics (NRC-HAA) research centre, slated to be deployed on multiple future AO instruments. REVOLT has provided the first on-sky demonstration of First Light Imaging’s C-Blue-One CMOS camera as a Shack-Hartmann Wavefront Sensor (SH-WFS), and demonstrated injection of the science PSF into a single mode fiber to feed experimental Spectral Correlation Sensor technology being developed to detect gas signatures in planetary atmospheres. Since its initial commissioning as a Single Conjugate AO (SCAO) system, an open loop arm, the GIRMOS Open Loop Demonstration (GOLD) arm, has been added to test OL calibration and control, and a Pyramid WFS (PWFS) arm has been added with the goal first of testing the Gemini Planet Imager 2 (GPI-2) HEART pipeline, as well as provide an on going test platform for PWFS research. This paper provides a full description of the current REVOLT system, summarizes the performance of each experiment conducted to date, highlights future plans and openly invites proposals for collaboration from the AO community.
In ground-based astronomy, the ability to couple the light into single-mode fibers (SMFs) is limited by atmospheric turbulence, which prohibits the use of many astrophotonic instruments. We propose a silicon-on-insulator photonic chip capable of coherently coupling the out-of-phase beamlets from the subapertures of a telescope pupil into an SMF. The PIC consists of an array of grating couplers used to inject the light from free space into single-mode waveguides on a chip. Metalic heaters modulate the refractive index of a coiled section of the waveguides, facilitating the co-phasing of the propagating modes. The beamlets can then be coherently combined to efficiently deliver the light to an output SMF. In an adaptive optics system, the phase corrector would act as a deformable mirror commanded by a controller that takes phase measurements from a wavefront sensor. We present experimental results for the PIC tested on an AO testbed and compare the performance to simulations.
Astronomy-grade cameras with robust performance and heritage in the space environment have long been costly, substantially limiting capacity for space-based astronomy and creating a resource barrier to access. Additionally, ultraviolet observations have historically been limited by the low-sensitivity of most sensors in this wavelength range. The LUVCam program is designed to address both issues, providing a high-performance, low-cost, UV/optical camera system sufficiently capable to support a wide-array of space-based astronomy missions. LUVCam features a large format, low-noise, large pixel, and high quantum efficiency, commercial-off-the-shelf backside illuminated CMOS sensor, packaged with custom built readout electronics and thermomechanical structure. LUVCam is ITAR-free, and cheap to fabricate, opening up new opportunities for access to space telescopes. LUVCam has reached TRL 6, and has passed qualification testing for operation in low-earth orbit, with competitive performance from 200-900 nm. LUVCam is manifested for multiple near-term orbital missions, including a technology demonstration CubeSat, and a UV transient astronomy SmallSat.
The MMT Adaptive optics exoPlanet characterization System (MAPS) is an exoplanet characterization program that encompasses instrument development, observational science, and education. The instrument we are developing for the 6.5m MMT observatory is multi-faceted, including a refurbished 336-actuator adaptive secondary mirror (ASM); two pyramid wavefront sensors (PyWFS's); a 1-kHz adaptive optics (AO) control loop; a high-resolution and long-wavelength upgrade to the Arizona infraRed Imager and Echelle Spectrograph (ARIES); and a new-AO-optimized upgrade to the MMT-sensitive polarimeter (MMT-Pol). With the completed MAPS instrument, we will execute a 60-night science program to characterize the atmospheric composition and dynamics of ~50-100 planets around other stars. The project is approaching first light, anticipated for Summer/Fall of 2022. With the electrical and optical tests complete and passing the review milestone for the ASM’s development, it is currently being tuned. The PyWFS's are being built and integrated in their respective labs: the visible-light PyWFS at the University of Arizona (UA), and the infrared PyWFS at the University of Toronto (UT). The top-level AO control software is being developed at UA, with an on-sky calibration algorithm being developed at UT. ARIES development continues at UA, and MMT-Pol development is at the University of Minnesota. The science and education programs are in planning and preparation. We will present the design and development of the entire MAPS instrument and project, including an overview of lab results and next steps.
The MMTO Adaptive optics exoPlanet characterization System (MAPS) is an ongoing upgrade to the 6.5-meter MMT Observatory on Mount Hopkins in Arizona. MAPS includes an upgraded adaptive secondary mirror (ASM), upgrades to the ARIES spectrograph, and a new AO system containing both an optical and near-infrared (NIR; 0.9-1.8 μm) pyramid wavefront sensor (PyWFS). The NIR PyWFS will utilize an IR-optimized double pyramid coupled with a SAPHIRA detector: a low-read noise electron Avalanche Photodiode (eAPD) array. This NIR PyWFS will improve MAPS’s sky coverage by an order of magnitude by allowing redder guide stars (e.g. K & M-dwarfs or highly obscured stars in the Galactic plane) to be used. To date, the custom designed cryogenic SAPHIRA camera has been fully characterized and can reach sub-electron read noise at high avalanche gain. In order to test the performance of the camera in a closed-loop environment prior to delivery to the observatory, an AO testbed was designed and constructed. In addition to testing the SAPHIRA’s performance, the testbed will be used to test and further develop the proposed on-sky calibration procedure for MMTO’s ASM. We will report on the anticipated performance improvements from our NIR PyWFS, the SAPHIRA’s closed-loop performance on our testbed, and the status of our ASM calibration procedure.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.