CTA prototype telescope, ASTRI, achieves first light

The ASTRI is one of three Small-Sized Telescope (SST)
designs being prototyped. SSTs will outnumber all the other
telescopes with 70 planned to be spread out over several square
kilometers in the southern hemisphere array only. This is
because very high-energy gamma-ray showers produce a large
amount of Cherenkov light, and the SST is sensitive to the
highest energy gamma rays (between a few TeV and 300 TeV).
Credit: CTA Collaboration

During the nights of 25 and 26 May, the camera of the ASTRI
telescope prototype recorded its first ever Cherenkov light
while undergoing testing at the astronomical site of Serra La
Nave (Mount Etna) in Sicily managed by INAF-Catania. This
comes not long after its optical validation
was achieved in November 2016
. This accomplishment was
the first optical demonstration for astronomical telescopes
using the novel Schwarzschild Couder dual-mirror design. The
ASTRI telescope is a proposed small-sized telescope design
for the Cherenkov Telescope Array (CTA).

Although the camera was not fully configured, the ASTRI team
was still able to capture its first Cherenkov light and produce
beautiful images of the showers generated by cosmic rays in the
Earth’s atmosphere. This information will allow scientists to
reconstruct the direction of gamma-ray photons emitted from
celestial sources (indicated by the yellow line on the image on
the left). The camera is based on novel SiPM small pixel
sensors (7 mm x 7 mm) and CITIROC ASICS peak-finder front-end
electronics. The camera was specifically designed to fit on the
dual mirror ASTRI telescopes for covering a large field of view
of 10 x 10 degrees.

“The results gathered from the images are very much in line
with the performance expectations established in the lab,
proving the functionality of the camera for the ASTRI
telescopes,” said Osvaldo Catalano, astronomer at the
INAF-Palermo Institute and leader of the ASTRI camera
development program. “The ASTRI team’s achievement is an
important milestone and a big step toward the pre-production
phase of ASTRI and CTA,” said Giovanni Pareschi, astronomer at
the INAF-Milano and principal investigator of the ASTRI
project.

Three classes of telescope types are required to cover the full
CTA very-high energy range (20 GeV to 300 TeV): Medium-Sized
Telescopes (12 m diameter dish) will cover CTA’s core energy
range (100 GeV to 10 TeV) while the Large-Sized Telescopes (23
m) and Small-Sized Telescopes (4 m) or SSTs are planned to
extend the energy range below 100 GeV and above a few TeV,
respectively. The ASTRI is one of three proposed SST designs
being prototyped and tested for CTA’s southern hemisphere
array. It uses an innovative dual-mirror Schwarzschild-Couder
configuration with a 4.3 m diameter primary mirror and a 1.8 m
monolithic secondary mirror. 

During the nights of 25 and 26 May 2017, the camera of the
ASTRI telescope prototype recorded its first ever Cherenkov light
while undergoing testing at the astronomical site of Serra La
Nave (Mount Etna) in Sicily managed by INAF-Catania. Credit:
Cherenkov Telescope Array Observatory

The SSTs will outnumber all the other telescopes with 70
planned to be spread out over several square kilometres in the
southern hemisphere array. Since the showers generated by very
high-energy gamma-rays (between a few TeV and 300 TeV) produce
a large amount of Cherenkov light, it is sufficient to build
telescopes with small mirrors to catch that light. The SSTs’
wide coverage and large number, spread over a large area, will
improve CTA’s ability to detect the highest energy gamma rays.

Explore further:

Prototype telescope demonstrates viability of novel
Schwarzschild-Couder design

More information: The ASTRI SST-2M Prototype: Camera and
Electronics. arxiv.org/abs/1307.5142

Provided by:
Cherenkov Telsecope Observatory

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