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1. Technical and scientific performance of the prototype Schwarzschild-Couder telescope for CTA

   https://doi.org/10.1117/12.2594580  

   Adams, Colin B.; Ambrosi, Giovanni; Ambrosio, Michelangelo; Aramo, Carla; Batista, Pedro I.; Benbow, Wystan; Bertucci, Bruna; Bissaldi, Elisabetta; Bitossi, Massimiliano; Boiano, Alfonso; et al (August 2021, Proceedings Volume 11820, Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems III;)

   Hallibert, Pascal; Hull, Tony B.; Kim, Daewook; Keller, Fanny (Ed.)

   The Cherenkov Telescope Array (CTA) is the next-generation ground-based observatory for very-high-energy gamma rays. One candidate design for CTA's medium-sized telescopes consists of the Schwarzschild-Couder Telescope (SCT), featuring innovative dual-mirror optics. The SCT project has built and is currently operating a 9.7-m prototype SCT (pSCT) at the Fred Lawrence Whipple Observatory (FLWO); such optical design enables the use of a compact camera with state-of-the art silicon photomultiplier detectors. A partially-equipped camera has recently successfully detected the Crab Nebula with a statistical significance of 8.6 standard deviations. A funded upgrade of the pSCT focal plane sensors and electronics is currently ongoing, which will bring the total number of channels from 1600 to 11328 and the telescope field of view from about 2.7° to 8° . In this work, we will describe the technical and scientific performance of the pSCT. 

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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 resolution 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. 

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3. 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 optical 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. 

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4. 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 ASICs 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. 

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5. A near-infrared pyramid wavefront sensor for the MMT

   https://doi.org/10.1117/12.2629419  

   Taylor, Jacob; Sivanandam, Suresh; Anugu, Narsireddy; Butko, Adam; Chen, Shaojie; Durney, Olivier; Hardy, Tim; Lamb, Masen; Montoya, Manny; Morzinski, Katie M.; et al (August 2022, Proceedings of the SPIE)

   Schmidt, Dirk; Schreiber, Laura; Vernet, Elise (Ed.)

   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. 

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