Prototype Schwarzschild-Couder Telescope for the Cherenkov Telescope Array: Commissioning the Optical System
Creators: name: Adams, C. B.
name: Ambrosi, G.
name: Ambrosio, M.
name: Aramo, C.
name: Batista, P. I.
name: Benbow, W.
name: Bertucci, B.
name: Bissaldi, E.
name: Bitossi, M.
name: Boiano, A.
name: Bonavolontà, C.
name: Bose, R.
name: Brill, A.
name: Buckley, J. H.
name: Cameron, R. A.
name: Canestrari, R.
name: Capasso, M.
name: Caprai, M.
name: Covault, C. E.
name: Depaoli, D.
name: Di Venere, L.
name: Errando, M.
name: Fegan, S.
name: Feng, Q.
name: Fiandrini, E.
name: Furniss, A.
name: Gent, A.
name: Giglietto, N.
name: Giordano, F.
name: Giro, E.
name: Halliday, R.
name: Hervet, O.
name: Humensky, T. B.
name: Incardona, S.
name: Ionica, M.
name: Jin, W.
name: Kieda, D.
name: Licciulli, F.
name: Loporchio, S.
name: Marsella, G.
name: Masone, V.
name: Meagher, K.
name: Meures, T.
name: Mode, B. A. W.
name: Mognet, S. A. I.
name: Mukherjee, R.
name: Nieto, D.
name: Okumura, A.
name: Otte, N.
name: Pantaleo, F. R.
name: Paoletti, R.
name: Pareschi, G.
name: Di Pierro, F.
name: Pueschel, E.
name: Ribeiro, D.
name: Riitano, L.
name: Roache, E.
name: Rousselle, J.
name: Rugliancich, A.
name: Santander, M.
name: Shang, R.
name: Stiaccini, L.
name: Taylor, L. P.
name: Tosti, L.
name: Tovmassian, G.
name: Tripodo, G.
name: Vagelli, V.
name: Valentino, M.
name: Vandenbroucke, J.
name: Vassiliev, V. V.
name: Williams, D. A.
name: Yu, P.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Optics (physics.optics)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: A prototype Schwarzschild-Couder Telescope (pSCT) has been constructed at the Fred Lawrence Whipple Observatory as a candidate for the medium-sized telescopes of the Cherenkov Telescope Array Observatory (CTAO). CTAO is currently entering early construction phase of the project and once completed it will vastly improve very high energy gamma-ray detection component in multi-wavelength and multi-messenger observations due to significantly improved sensitivity, angular resolution and field of view comparing to the current generation of the ground-based gamma-ray observatories H.E.S.S., MAGIC and VERITAS. The pSCT uses a dual aspheric mirror design with a $9.7$ m primary mirror and $5.4$ m secondary mirror, both of which are segmented. The Schwarzschild-Couder (SC) optical system (OS) selected for the prototype telescope achieves wide field of view of $8$ degrees and simultaneously reduces the focal plane plate scale allowing an unprecedented compact ($0.78$m diameter) implementation of the high-resolution camera ($6$mm/ $0.067$deg per imaging pixel with $11,328$ pixels) based on the silicon photo-multipliers (SiPMs). The OS of the telescope is designed to eliminate spherical and comatic aberrations and minimize astigmatism to radically improve off-axis imaging and consequently angular resolution across all the field of view with respect to the conventional single-mirror telescopes. Fast and high imaging resolution OS of the pSCT comes with the challenging submillimeter-precision custom alignment system, which was successfully demonstrated with an on-axis point spread function (PSF) of $2.9$ arcmin prior to the first-light detection of the Crab Nebula in 2020. Ongoing and future commissioning activities are reported.