Status of the Large Size Telescopes of the Cherenkov Telescope Array
Pith reviewed 2026-05-24 18:43 UTC · model grok-4.3
The pith
The first fully equipped Large Size Telescope was installed at the CTA-North site in 2018 with commissioning expected to finish in 2019.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
A fully equipped LST has been installed at the CTA-North site in 2018 and is expected to be finished commissioning during 2019. The remaining three LSTs in the north will be installed by 2022.
What carries the argument
The Large Size Telescope (LST), a 110-ton movable structure carrying a 23 m tessellated parabolic mirror corrected by actuators, a 2-ton camera with 1855 high-QE PMTs, and 1 GS/s embedded readout.
If this is right
- The northern LST sub-array will extend CTA sensitivity down to approximately 20 GeV.
- The 20-second slew capability will allow prompt follow-up observations of gamma-ray bursts.
- The camera design supports sustained data acquisition rates above 10 kHz.
Where Pith is reading between the lines
- Successful early commissioning of the first LST would provide a template for the three southern LSTs.
- If the northern array reaches four telescopes by 2022, joint observations with other CTA telescopes could begin before the full southern array is complete.
Load-bearing premise
The installation date of 2018 and the 2019 commissioning timeline accurately reflect the physical completion and operational readiness of the hardware.
What would settle it
On-site photographs or official CTA project announcements from mid-to-late 2019 confirming whether the first LST has completed commissioning and begun regular data taking.
read the original abstract
The Cherenkov Telescope Array (CTA) will consist of two arrays of Imaging Atmospheric Cherenkov Telescopes (IACTs) at the northern and southern hemispheres. CTA will feature IACTs with mirrors of three different sizes optimized to cover different energy ranges. The proposed sub-arrays of four Large Size Telescopes (LST) at CTA-North and CTA-South target the lowest energy range between around 20 GeV and 100 GeV. Thanks to their low weight of around 110 tons the LSTs can move by 180 deg in azimuth in 20 seconds for Gamma Ray Burst (GRB) follow-up. An LST has a tessellated parabolic mirror of 23 m diameter equipped with a system of actuators to correct for gravity-induced deformations during data taking. Its low-weight 2 ton camera at the prime focus has a 4.5 deg diameter, 1855 high QE PMTs and an embedded readout with 1 GSps sampling speed designed for data acquisition rates exceeding 10 kHz. A fully equipped LST has been installed at the CTA-North site in 2018 and is expected to be finished commissioning during 2019. The remaining three LSTs in the north will be installed by 2022. We will review the status of the LSTs, describe the installation of the first LST and report on the first results of the commissioning tests.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript is a status report on the Large Size Telescopes (LSTs) of the Cherenkov Telescope Array (CTA). It describes the LST design, including a 23 m tessellated parabolic mirror with actuator corrections, ~110 ton weight enabling 180 deg azimuth slew in 20 s for GRB follow-up, and a 2-ton prime-focus camera with 4.5 deg field, 1855 high-QE PMTs, and 1 GSps embedded readout supporting >10 kHz rates. The central factual claims are that one fully equipped LST was installed at CTA-North in 2018 with commissioning expected to conclude in 2019, and that the remaining three northern LSTs will be installed by 2022. The paper reviews overall LST status, details the first LST installation, and presents initial commissioning test results.
Significance. If the reported timelines and hardware specifications hold, the paper supplies a useful reference for the gamma-ray astronomy community on the progress of CTA's low-energy sub-array. The LSTs target the 20-100 GeV range and rapid slewing capability, both of which are relevant for transient science; documenting installation milestones and basic performance metrics therefore aids planning for future observations and data analysis.
Simulated Author's Rebuttal
We thank the referee for their review of the manuscript and for the recommendation to accept.
Circularity Check
No significant circularity
full rationale
This is a factual project status report on LST hardware installation dates, commissioning timelines, and technical specifications. No equations, derivations, fitted parameters, or model predictions appear anywhere in the text. Central claims are presented as direct statements of project documentation rather than results derived from internal assumptions or self-citations. The paper is self-contained against external benchmarks with no opportunity for the enumerated circularity patterns.
discussion (0)
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