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An adaptive secondary mirror (ASM) with novel actuator technology is being designed and built for the UH88 telescope as a demonstration of a new generation of ASMs that might be deployed at ground based observatories such as Keck, Subaru, and TMT. Before putting the ASM on the telescope, a set of calibrations and character- izations need to be made in the lab. The crucial lab characterizations of the ASM are to measure its influence functions, and its surface shape when powered and unpowered. To measure these, we develop a novel and inexpensive optical metrology approach using phase measuring deflectometry. This paper describes the simulations we wrote to model the deflectometry method, our data acquisition/analysis pipeline, and a lab prototype sys- tem we built that demonstrates its feasibility on a microelectromechanical systems (MEMS) deformable mirror. Based on the information gained through the deflectometry simulation and the setup prototype, we conclude that phase measuring deflectometry is a reasonable method for obtaining the influence functions but that the absolute surface shape of the ASM will be limited by our knowledge of the placement of components within the deflectometry setup itself. We discuss challenges with extending this approach to larger convex adaptive secondary mirrors. 

We report on progress at the University of Hawaii on the integration and testing setups for the adaptive secondary mirror (ASM) for the University of Hawaii 2.2-meter telescope on Maunakea, Hawaii. We report on the development of the handling fixtures and alignment tools we will use along with progress on the optical metrology tools we will use for the lab and on-sky testing of the system. 

Adaptive Optics (AO) used in ground based observatories can be strengthened in both design and algorithms by a more detailed understanding of the atmosphere they seek to correct. Nowhere is this more true than on Maunakea, where a clearer profile of the atmosphere informs AO system development from the small separations of Extreme AO (ExAO) to the wide field Ground Layer AO (GLAO). Employing telemetry obtained from the ımaka GLAO demonstrator on the University of Hawaii 2.2-meter telescope, we apply a wind profiling method that identifies turbulent layer velocities through spatial-temporal cross correlations of multiple wavefront sensors (WFSs). We compare the derived layer velocities with nearby wind anemometer data and meteorological model predictions of the upper wind speeds and discuss similarities and differences. The strengths and limitations of this profiling method are evaluated through successful recovery of injected, simulated layers into real telemetry. We detail the profilers’ results, including the percentage of data with viable estimates, on four characteristic ımaka observing runs on open loop telemetry throughout both winter and summer targets. We report on how similar layers are to external measures, the confidence of these results, and the potential for future use of this technique on other multi conjugate AO systems. 

Early adaptive optics (AO) systems were designed with knowledge of a site’s distribution of Fried parameter (r0) and Greenwood time delay (τ0) values. Recent systems have leveraged additional knowledge of the distribution of turbulence with altitude. We present measurements of the atmosphere above Maunakea, Hawaii and how the temporal properties of the turbulence relate to tomographic reconstructions. We combine archival telemetry collected by ‘imaka—a ground layer AO (GLAO) system on the UH88” telescope—with data from the local weather towers, weather forecasting models, and weather balloon launches, to study how frequently one can map a turbulent layer’s wind vector to its altitude. Finally, we present the initial results of designing a new GLAO control system based off of these results, an approach we have named “temporal tomography.” 

A consortium of industrial and academic partners, coordinated by TNO, is working on the realization of a 620mm adaptive secondary mirror (ASM) for the University of Hawaii’s 2.2-meter telescope. The ASM consists of a 620mm-diameter slumped convex aspherical mirror shell, manipulated by 210 variable-reluctance actuators mounted on a light-weighted support frame. The mirror shell is manufactured to the required accuracy at low cost through slumping. The actuators are driven by dedicated PWM current drivers and commanded through a real-time FPGA-based interface. After successful performance testing of several laboratory prototypes, this project will provide the definitive on-sky demonstration of this new technology. We report on the manufacturing and testing of the major subsystems, and on the integration status of the ASM as a whole.