Scientists to inaugurate a new type of gamma ray telescope at Whipple Observatory

The prototype Schwarzschild-Couder Telescope (pSCT) is designed as a pathfinder telescope for the Cherenkov Telescope Array

pSCT telescope
The prototype Schwarzschild-Couder Telescope (pSCT) is a novel type of gamma-ray telescope designed for the Cherenkov Telescope Array (CTA). (Photo by Amy Oliver, Fred Lawrence Whipple Observatory, Center for Astrophysics, Harvard & Smithsonian)

A new type of gamma-ray telescope will be unveiled January 17 in an inauguration event at the Fred Lawrence Whipple Observatory in Amado, Arizona. Expected to see first light in early 2019, the telescope is a prototype Schwarzschild-Couder Telescope (pSCT) designed for the Cherenkov Telescope Array (CTA), the next generation ground-based observatory for gamma-ray astronomy at very high energies.

David Williams, a researcher in the Santa Cruz Institute for Particle Physics (SCIPP) at UC Santa Cruz, chairs the CTA-US Consortium.

The inauguration of the pSCT is an exciting moment for the institutions involved in its development and construction,” Williams said. “The first of its kind in the history of gamma-ray telescopes, the SCT design is expected to boost CTA performance towards the theoretical limit of the technology.”

The CTA Observatory, for which construction will begin in 2019, will be the world’s largest and most sensitive high-energy gamma-ray observatory, with more than 100 telescopes located in the northern and southern hemispheres.

The 9.7-meter aperture pSCT is a pathfinder telescope for use in the CTA and exploits a novel optical design. Its complex dual-mirror optical system improves on the single-mirror designs traditionally used in gamma-ray telescopes by dramatically enhancing the optical quality of their focused light over a large region of the sky, and by enabling the use of compact, highly-efficient photo-sensors in the telescope camera.

Ultimately, the SCT is designed to improve CTA’s ability to detect very-high-energy gamma-ray sources, which may also be sources of neutrinos and gravitational waves,” said Vladimir Vassiliev, principal investigator of the pSCT. “Once the SCT technology is demonstrated at FLWO, it is hoped that SCTs will become a part of at least one of the two CTA arrays, located in each of the northern and southern hemispheres.”

The CTA Observatory (CTAO) will consist of 118 telescopes of three different sizes and is expected to detect sources of gamma rays in the energy range 20 GeV to 300 TeV, with about ten times increased sensitivity compared to any current observatory. Notable for providing improved gamma-ray angular resolution and its very-high-resolution camera (more than 11,000 pixels), the SCT is proposed for the medium-sized CTA telescopes and will primarily contribute to the middle of CTA’s energy range (80 GeV to 50 TeV).

The SCT and other telescopes at CTA will greatly improve upon current gamma-ray research being conducted at HAWC, HESS, MAGIC, and VERITAS, the last of which is located at the Fred Lawrence Whipple Observatory,” said VERITAS Director Wystan Benbow. “Gamma-ray observatories like VERITAS have been operating for 12 to 16 years, and their many successes have brought very-high-energy gamma-ray astronomy into the mainstream, and have made many exciting discoveries. We hope CTA will supersede VERITAS around 2023, and it will be used to continue to build upon the 50 years of gamma-ray research at the Whipple Observatory and elsewhere.”

The Whipple Observatory is operated by the Harvard-Smithsonian Center for Astrophysics.

The SCT optical design was first conceptualized by U.S. members of CTA in 2006, and the construction of the pSCT was funded in 2012. The member institutions of the CTA-US Consortium include the UC Santa Cruz Department of Physics and the Santa Cruz Institute for Particle Physics. Preparation of the pSCT site at the base of Mt. Hopkins in Amado, AZ, began in late 2014, and the steel structure was assembled on site in 2016. The installation of pSCT’s 9.7-meter primary mirror surface, consisting of 48 aspheric mirror panels, occurred in early 2018, and was followed by the camera installation in June 2018 and the 5.4-meter secondary mirror surface installation, consisting of 24 aspheric mirror panels, in August 2018.

Leading up to the inauguration and in preparation for first light, scientists opened the telescope’s optical surfaces in January 2019. The SCT is based on a 114-year-old dual-mirror optical system first proposed by Karl Schwarzschild in 1905. It became possible to construct only recently as a result of critical research and development progress made at both the Brera Astronomical Observatory and Media Lario Technologies Incorporated in Italy.

The pSCT was made possible by funding through the U.S. National Science Foundation Major Research Instrumentation program and by the contributions of thirty institutions and five critical industrial partners across the United States, Italy, Germany, Japan, and Mexico. 

More information about the pSCT is available online at