Star Tracking Paper

Title

Star tracking for pointing determination of Imaging Atmospheric Cherenkov Telescopes. Application to the Large-Sized Telescope of the Cherenkov Telescope Array.

Corresponding Authors

Mykhailo Dalchenko mykhailo.dalchenko@unige.ch

Matthieu Heller matthieu.heller@unige.ch

Abstract

We present a novel approach to the determination of the pointing of Imaging Atmospheric Cherenkov Telescopes (IACTs) using the trajectories of the stars in their cameras' field of view. The method starts with the reconstruction of the star positions, taking into account the point spread function of the telescope, to achieve satisfying reconstruction accuracy. A simultaneous fit of all reconstructed star trajectories is then performed with the orthogonal distance regression (ODR) method. ODR allows us correctly include the star position uncertainties and use time as an independent variable. Having time as an independent variable in the fit makes it more flexible towards changes in the positions of stars when tracking.

This method can be applied to any IACT. In this paper, we use the Large-Sized Telescope (LST) data to validate it as a useful tool for pointing reconstruction during regular data taking. The simulation studies show that the accuracy and precision of the method are comparable with the design requirements on the pointing accuracy of the LST. With the typical IACT event acquisition rate of 10~kHz, the method can achieve up to 50~Hz pointing monitoring rate. The application of the method to the Large-Sized Telescope prototype (LST-1) commissioning data shows the stable pointing performance of the telescope, which meets the online pointing accuracy requirements.

Draft progress

File:Star tracking paper-v1.pdf

The v2 revision together with comments and answers can be found at the CDS entry here: https://cds.cern.ch/record/2838837/

Final draft of the paper including all comments posted on CDS: https://www.lst1.iac.es/wiki/images/8/8e/Star_tracking_paper-final-draft.pdf

Final draft of the paper including LST collaboration comments: https://www.lst1.iac.es/wiki/images/b/b1/Star_tracking_paper-final-draft-with-lst-comments.pdf

Changelog:

 - Updated acknowledgements section with CZ funding agencies
 - Updated authorlist
 - Addressed M. Doro's comments

Thanks to everyone who participated in the review!