Mirror Position Determination for the Alignment of Cherenkov Telescopes

Abstract

Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures to map the faint Cherenkov light emitted in extensive air showers onto their image sensors. Segmented reflectors fulfill these needs using mass produced and light weight mirror facets. However, as the overall image is the sum of the individual mirror facet images, alignment is important. Here we present a method to determine the mirror facet positions on a segmented reflector in a very direct way. Our method reconstructs the mirror facet positions from photographs and a laser distance meter measurement which goes from the center of the image sensor plane to the center of each mirror facet. We use our method to both align the mirror facet positions and to feed the measured positions into our IACT simulation. We demonstrate our implementation on the 4 m First Geiger-mode Avalanche Cherenkov Telescope (FACT).

arXiv comment11 figures, small ray tracing performance simulation, and implementation demonstration

References in corpus (7)

• The First VERITAS Telescope
• Design and Operation of FACT -- The First G-APD Cherenkov Telescope
• The optical system of the H.E.S.S. imaging atmospheric Cherenkov telescopes, Part I: layout and components of the system
• The CAT Imaging Telescope for Very-High-Energy Gamma-Ray Astronomy
• A New Mirror Alignment System for the VERITAS Telescopes
• Bokeh Mirror Alignment for Cherenkov Telescopes
• Normalized and Asynchronous Mirror Alignment for Cherenkov Telescopes