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[Editor's Pick] Current Optics and Photonics Vol. 8 no. 1 (2024 February)

사무국 hit 306 date 2024-02-23

SLODAR System Development for Vertical Atmospheric Disturbance Profiling at Geochang Observatory

Ji Yong Joo1, Hyeon Seung Ha1, Jun Ho Lee1,2 *, Do Hwan Jung1,3, Young Soo Kim1,3, and Timothy Butterley4

 

Current Optics and Photonics  Vol. 8 No. 1 (2024 February) pp. 30-37
DOI: https://doi.org/10.3807/COPP.2024.8.1.30 

FIG. 1. Schematic diagram illustrating the crossed-beam method. This specific diagram depicts the construction of 8 layers of vertical profiling with 8 sub-aperture wavefront sensing [13].

Fig. 1  Schematic diagram illustrating the crossed-beam method. This specific diagram depicts the construction of 8 layers of vertical profiling with 8 sub-aperture wavefront sensing [13].

 

Keywords: Adaptive optics, Atmospheric turbulence, Fried parameter, Refractive index structure function (C2n), SLODAR
OCIS codes: (010.1330) Atmospheric turbulence; (120.4640) Optical instruments; (220.1080) Active or adaptive optics; (350.1260) Astronomical optics


Abstract
Implemented at the Geochang Observatory in South Korea, our slope detection and ranging (SLODAR) system features a 508 mm Cassegrain telescope (f /7.8), incorporating two Shack-Hartmann wave-front sensors (WFS) for precise measurements of atmospheric phase distortions, particularly from nearby binary or double stars, utilizing an 8 × 8 grid of sampling points. With an ability to reconstruct eight-layer vertical atmospheric profiles, the system quantifies the refractive index structure function (C2n) through the crossed-beam method. Adaptable in vertical profiling altitude, ranging from a few hundred meters to several kilometers, contingent on the separation angle of binary stars, the system operates in both wide (2.5 to 12.5 arcminute separation angle) and narrow modes (11 to 15 arcsecond separation angle), covering altitudes from 122.3 to 611.5 meters and 6.1 to 8.3 kilometers, respectively. Initial measurements at the Geochang Observatory indicated C values up to 181.7 meters with a Fried parameter (r0) of 8.4 centimeters in wide mode and up to 7.8 kilometers with an r0 of 8.0 centimeters in narrow mode, suggesting similar seeing conditions to the Bohyun Observatory and aligning with a comparable 2014–2015 seeing profiling campaign in South Korea.