A Low-Cost Portable SDIMM for Daytime Atmospheric Optical Turbulence Measurement in Observatory Site Testing: Primary Results from Ali Site
Atmospheric optical turbulence intensity, quantified by the Fried parameter (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Photonics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2304-6732/12/7/705 |
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| Summary: | Atmospheric optical turbulence intensity, quantified by the Fried parameter (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></math></inline-formula>), serves as a critical metric for astronomical site testing and selection. The Solar Differential Image Motion Monitor (SDIMM), adapted from the methodology of the Differential Image Motion Monitor (DIMM), is a dedicated instrument for daytime <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></math></inline-formula> measurements. Conventional SDIMM systems typically employ telescopes with apertures ≥30 cm and reconstruct wavefront segmentation at the exit pupil, resulting in bulky configurations that impede portability. To address the demands of multi-site surveys, we developed a low-cost, portable SDIMM system that directly adopts the DIMM optical path without backend wavefront reconstruction, instead deriving <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></math></inline-formula> through image processing algorithms. Integrated with a 20 cm aperture telescope, the system achieves a total weight of <20 kg, significantly enhancing field portability. This paper details the instrument’s architecture, measurement principles, and comparative tests with a traditional SDIMM, demonstrating strong consistency between the two systems. Field measurements conducted at the Ali Observatory (elevation: 5050 m) from 16 August to 10 December 2024 yielded the site’s first continuous daytime <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></math></inline-formula> dataset, with values ranging from 1.5 cm to 12 cm and a mean of 4.09 cm. The compact SDIMM provides a cost-effective and easily deployable solution for comparative daytime <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mn>0</mn></msub></semantics></math></inline-formula> assessments across multiple candidate astronomical sites. |
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| ISSN: | 2304-6732 |