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1. Alignment of the optical system of the 9.7-m prototype Schwarzchild-Coulder Telescope

   https://doi.org/10.1117/12.2564653  

   Adams, C.~B.~ ; Alfaro, R.~ ; G.~Ambrosi, Ambrosi ; Ambrosio, M.~ ; Aramo, C.~ ; Benbow, W.~ ; Bertucci, B.~ ; Bissaldi, E.~ ; Bitossi, M.~ ; Boiano, A.~ ; et al ( December 2020 , Proceedings Volume 11445, Ground-based and Airborne Telescopes VIII;)

   Marshall, Heather K. ; Spyromilio, Jason ; Usuda, Tomonori (Ed.)

   The novel 9.7m Schwarzschild-Couder Telescope (SCT), utilizing aspheric dual-mirror optical system, has been constructed as a prototype medium size x-ray telescope for the Cherenkov Telescope Array (CTA) observatory. The prototype SCT (pSCT) is designed to achieve simultaneously the wide (≥ 8°) field of view and the superior imaging resolution (0.067 per pixel) to significantly improve scientific capabilities of the observatory in conducting the sky surveys, the follow-up observations of multi-messenger transients with poorly known initial localization and the morphology studies of x-ray sources with angular extent. In this submission, we describe the hardware and software implementations of the telescope opticalmore »system as well as the methods specifically developed to align its complex optical system, in which both primary and secondary mirrors are segmented. The pSCT has detected Crab Nebula in June 2020 during ongoing commissioning, which was delayed due to worldwide pandemic and is not yet completed. Verification of pSCT performance is continuing and further improvement of optical alignment is anticipated.« less
2. Verification of the optical system of the 9.7-m prototype Schwarzschild-Couder Telescope

   https://doi.org/10.1117/12.2568134  

   Adams, Colin ; Alfaro, Ruben ; Ambrosi, Giovanni ; Ambrosio, Michelangelo ; Aramo, Carla ; Benbow, Wystan ; Bertucci, Bruna ; Bissaldi, Elisabetta ; Bitossi, M. ; Boiano, Alfonso ; et al ( August 2020 , SPIE Optical Engineering + Applications, 2020, Online Only)

   Sasián, José ; Youngworth, Richard N. (Ed.)

   For the first time in the history of ground-based x-ray astronomy, the on-axis performance of the dual mirror, aspheric, aplanatic Schwarzschild-Couder optical system has been demonstrated in a 9:7-m aperture imaging atmospheric Cherenkov telescope. The novel design of the prototype Schwarzschild-Couder Telescope (pSCT) is motivated by the need of the next-generation Cherenkov Telescope Array (CTA) observatory to have the ability to perform wide (>=8°) field-of-view observations simultaneously with superior imaging of atmospheric cascades (resolution of 0:067 per pixel or better). The pSCT design, if implemented in the CTA installation, has the potential to improve significantly both the x-ray angular resolutionmore »and the off-axis sensitivity of the observatory, reaching nearly the theoretical limit of the technique and thereby making a major impact on the CTA observatory sky survey programs, follow-up observations of multi-messenger transients with poorly known initial localization, as well as on the spatially resolved spectroscopic studies of extended x-ray sources. This contribution reports on the initial alignment procedures and point-spread-function results for the challenging segmented aspheric primary and secondary mirrors of the pSCT.« less
3. The upgraded camera for the prototype Schwarzschild-Couder Telescope of the Cherenkov Telescope Array

   https://doi.org/10.1117/12.2530431  

   Paoletti, Riccardo ( September 2019 , The upgraded camera for the prototype Schwarzschild-Couder Telescope of the Cherenkov Telescope Array)

   The Schwarzschild-Couder Telescope (SCT) is a mid-size telescope proposed for the Cherenkov Telescope Array. In order to substantially improve the eld of view and image resolution compared to i traditional Davies-Cotton telescopes, innovative solutions are foreseen in the design, like the use of Silicon Photomultipliers (SiPM) as light sensors and waveform digitizers for recording the fast light signals from atmospheric showers. A project is now underway to upgrade the camera by increasing its pixel count to 11; 328 pixels and field of view of 8:0. The camera electronics has been completely redesigned by using new waveform digitizer and trigger ASICsmore »with the final goal of lowering the gamma-ray energy threshold and therefore provide an excellent instrument tailored for extended sources investigations and multi-messenger astronomy.« less
4. The wide-field infrared transient explorer (WINTER)

   https://doi.org/10.1117/12.2561210  

   Lourie, Nathan P. ; Baker, John W. ; Burruss, Richard S. ; Egan, Mark D. ; Furész, Gábor ; Frostig, Danielle ; Garcia-Zych, Allan A. ; Ganciu, Nicolae ; Haworth, Kari ; Hinrichsen, Erik ; et al ( December 2020 , X-Ray, Optical, and Infrared Detectors for Astronomy IX)

   Evans, Christopher J. ; Bryant, Julia J. ; Motohara, Kentaro (Ed.)

   The Wide-Field Infrared Transient Explorer (WINTER) is a new infrared time-domain survey instrument which will be deployed on a dedicated 1 meter robotic telescope at the Palomar Observatory. WINTER will perform a seeing-limited time domain survey of the infrared (IR) sky, with a particular emphasis on identifying r -process material in binary neutron star (BNS) merger remnants detected by LIGO. We describe the scientific goals and survey design of the WINTER instrument. With a dedicated trigger and the ability to map the full LIGO O4 positional error contour in the IR to a distance of 190 Mpc within four hours,more »WINTER will be a powerful kilonova discovery engine and tool for multi-messenger astrophysics investigations. In addition to follow-up observations of merging binaries, WINTER will facilitate a wide range of time-domain astronomical observations, all the while building up a deep coadded image of the static infrared sky suitable for survey science. WINTER's custom camera features six commercial large-format Indium Gallium Arsenide (InGaAs) sensors and a tiled optical system which covers a <1-square-degree field of view with 90% fill factor. The instrument observes in Y, J and a short-H (Hs) band tuned to the long-wave cutoff of the InGaAs sensors, covering a wavelength range from 0.9 - 1.7 microns. We present the design of the WINTER instrument and current progress towards final integration at the Palomar Observatory and commissioning planned for mid-2021.« less
5. Okayama Astrophysical Observatory Wide-Field Camera

   https://doi.org/10.1093/pasj/psz117  

   Yanagisawa, Kenshi ; Shimizu, Yasuhiro ; Okita, Kiichi ; Kuroda, Daisuke ; Tsutsui, Hironori ; Koyano, Hisashi ; Izumiura, Hideyuki ; Yoshida, Michitoshi ; Ohta, Kouji ; Kawai, Nobuyuki ; et al ( November 2019 , Publications of the Astronomical Society of Japan)

   We report on the development of a wide-field near-infrared (0.9–2.5$\, \mu$m) camera built as a renewal of the existing classical Cassegrain 0.91 m telescope at Okayama Astrophysical Observatory. The optics system was replaced with fast hybrid optics (f/2.5) composed of forward Cassegrain optics and quasi-Schmidt optics, which results in an effective image circle of 52 mm diameter on the focal plane. The new camera, called the Okayama Astrophysical Observatory Wide-Field Camera (OAOWFC), has imaging capabilities in the $Y$, $J$, $H$, and $K_{\rm s}$ bands over a field of view of $0.^{\!\!\!\circ }47 \times 0.^{\!\!\!\circ }47$ with a HAWAII-1 HgCdTe PACE focalmore »plane array. The primary purpose of OAOWFC is to search for variability in the Galactic plane in the $K_{\rm s}$ band and to promptly follow up transients. We have demonstrated a photometric repeatability of 2% in the densest field in the northern Galactic plane and successfully discovered previously unreported variable stars. The observations of OAOWFC are fully autonomous, and we started scientific operations in 2015 April.

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