The Optical System for the Prototype Schwarzschild-Couder Telescope for the Cherenkov Telescope Array

The Schwarzschild-Couder Telescope (SCT) is a candidate for Medium-Sized Telescopes of the Cherenkov Telescope Array (CTA). CTA will enable improvements in multi-wavelength and multi-messenger observations with respect to the current ground-based gamma-ray instruments, due to higher angular resolution, increased sensitivity, and energy coverage extending from 20 GeV to 300 TeV. A prototype SCT (pSCT) has been constructed at the Fred Lawrence Whipple Observatory with a novel optical system consisting of a dual-mirror design with a 9.7-m primary mirror and 5.4-m segmented secondary mirror. It has a wide field of view (about 8 degrees), allows a compact, high-resolution SiPM camera (0.067 deg per imaging pixel), and substantially improves the off-axis performance giving better angular resolution across all of the field of view with respect to single-mirror telescopes. The optical system requires a submillimeter-precision custom alignment system, which was successfully achieved with an on-axis PSF of 2.8 arcmin prior to first-light detection of the Crab Nebula in 2020. In this contribution, we report on the commissioning status, the alignment procedures, and some alignment results during the ongoing commissioning phase of the optical system of the prototype SCT.