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  1. A wide research base has documented the disproportional enrollment in K-12 special education and gifted and talented services across racial and socioeconomic lines. This study extends that knowledge base by integrating multiple population-level datasets to better understand predictors of access to and enrollment in gifted and talented services and tested whether these variables remained predictive after controlling for state mandate to provide services, average district achievement, and average school achievement. Results showed that states varied, with some serving 20% of their students as gifted and others serving 0%. Similarly, within-district income segregation, income-related achievement gaps, and parental education were dominantmore »predictors of a school offering gifted and talented services and the size of the population served, even after controlling for achievement and the presence of a state mandate. These findings suggest that gifted and talented programs are often made available based on school or community demographics rather than the needs of the students.« less
    Free, publicly-accessible full text available July 1, 2023
  2. Schmidt, Dirk ; Schreiber, Laura ; Vernet, Elise (Ed.)
    As part of the Keck All-sky Precision Adaptive optics (KAPA) project a laser Asterism Generator (AG) is being implemented on the Keck I telescope. The AG provides four Laser Guide Stars (LGS) to the Keck Adaptive Optics (AO) system by splitting a single 22W laser beam into four beams of equal intensity. We present the design and implementation of the AG for KAPA. We discuss the optical design and layout, the details of the mechanical design and fabrication, and the challenges of designing the assembly to fit into the limited available space on the Keck telescope.
    Free, publicly-accessible full text available August 29, 2023
  3. Schmidt, Dirk ; Schreiber, Laura ; Vernet, Elise (Ed.)
    We calculate an optical distortion solution for the OSIRIS Imager on the Keck I telescope, by matching observations of globular clusters to a Hubble reference catalogue. This solution can be applied to correct astrometric distortions in OSIRIS frames, improving the astrometric accuracy of observations. We model the distortion with a 5th order Legendre polynomial. The distortion we find matches the expected OSIRIS distortion, and has a fit error of 0.6 mas, but has large residuals of 7 mas. We are currently iterating on an improved reference frame to improve the residual. Additionally, we have installed the Precision Calibration Unit (PCU)more »on the Keck I optical bench, which will generates an artificial grid of stars for use in future distortion calculations.« less
    Free, publicly-accessible full text available August 30, 2023
  4. Free, publicly-accessible full text available May 4, 2023
  5. Schmidt, Dirk ; Schreiber, Laura ; Vernet, Elise (Ed.)
    The Keck All-Sky Precision Adaptive Optics (KAPA) system project will upgrade the Keck I AO system to enable laser tomography with a four laser guide star (LGS) asterism. This paper describes the new infrastructure which is being built for daytime calibration and testing of the KAPA tomographic algorithms.
    Free, publicly-accessible full text available August 29, 2023
  6. Schmidt, Dirk ; Schreiber, Laura ; Vernet, Elise (Ed.)
    The W. M. Keck Observatory Adaptive Optics (AO) facilities have been operating with a Field Programmable Gate Array (FPGA) based real time controller (RTC) since 2007. The RTC inputs data from various AO wavefront and tip/tilt sensors; and corrects image blurring from atmospheric turbulence via deformable and tip/tilt mirrors. Since its commissioning, the Keck I and Keck II RTCs have been upgraded to support new hardware such as pyramid wavefront and infrared tip-tilt sensors. However, they are reaching the limits of their capabilities in terms of processing bandwidth and the ability to interface with new hardware. Together with the Keckmore »All-sky Precision Adaptive optics (KAPA) project, a higher performance and a more reliable RTC is needed to support next generation capabilities such as laser tomography and sensor fusion. This paper provides an overview of the new RTC system, developed with our contractor/collaborators (Microgate, Swinburne University of Technology and Australian National University), and the initial on-sky performance. The upgrade includes an Interface Module to interface with the wavefront sensors and controlled hardware, and a Graphical Processing Unit (GPU) based computational engine to meet the system’s control requirements and to provide a flexible software architecture to allow future algorithms development and capabilities. The system saw first light in 2021 and is being commissioned in 2022 to support single conjugate laser guide star (LGS) AO, along with a more sensitive EMCCD camera. Initial results are provided to demonstrate single NGS & LGS performance, system reliability, and the planned upgrade for four LGS to support laser tomography.« less
    Free, publicly-accessible full text available August 29, 2023
  7. Free, publicly-accessible full text available April 21, 2023
  8. Arctic vegetation communities are rapidly changing with climate warming, which impacts wildlife, carbon cycling and climate feedbacks. Accurately monitoring vegetation change is thus crucial, but scale mismatches between field and satellite-based monitoring cause challenges. Remote sensing from unmanned aerial vehicles (UAVs) has emerged as a bridge between field data and satellite-based mapping. We assess the viability of using high resolution UAV imagery and UAV-derived Structure from Motion (SfM) to predict cover, height and aboveground biomass (henceforth biomass) of Arctic plant functional types (PFTs) across a range of vegetation community types. We classified imagery by PFT, estimated cover and height, andmore »modeled biomass from UAV-derived volume estimates. Predicted values were compared to field estimates to assess results. Cover was estimated with root-mean-square error (RMSE) 6.29-14.2% and height was estimated with RMSE 3.29-10.5 cm, depending on the PFT. Total aboveground biomass was predicted with RMSE 220.5 g m-2, and per-PFT RMSE ranged from 17.14-164.3 g m-2. Deciduous and evergreen shrub biomass was predicted most accurately, followed by lichen, graminoid, and forb biomass. Our results demonstrate the effectiveness of using UAVs to map PFT biomass, which provides a link towards improved mapping of PFTs across large areas using earth observation satellite imagery.« less
    Free, publicly-accessible full text available April 12, 2023
  9. Free, publicly-accessible full text available February 1, 2023
  10. Free, publicly-accessible full text available April 1, 2023