S-DIMM+ height characterization of day-time seeing using solar granulation

TL;DR

This paper introduces a novel method using solar granulation and Shack Hartmann sensors to characterize atmospheric seeing contributions up to 12 km height, aiding site selection and adaptive optics development for solar telescopes.

Contribution

The paper presents a new technique for evaluating atmospheric seeing layers using differential image displacements from solar granulation, improving height-resolved seeing measurements for solar telescopes.

Findings

Effective for Fried's parameter r_0 > 7.5 cm at ground level

Provides valuable data for site selection and adaptive optics design

Limitations due to large field-of-view affecting measurements at 30 km

Abstract

To evaluate site quality and to develop multi-conjugative adaptive optics systems for future large solar telescopes, characterization of contributions to seeing from heights up to at least 12 km above the telescope is needed. We describe a method for evaluating contributions to seeing from different layers along the line-of-sight to the Sun. The method is based on Shack Hartmann wavefront sensor data recorded over a large field-of-view with solar granulation and uses only measurements of differential image displacements from individual exposures, such that the measurements are not degraded by residual tip-tilt errors. We conclude that the proposed method allows good measurements when Fried's parameter r_0 is larger than about 7.5 cm for the ground layer and that these measurements should provide valuable information for site selection and multi-conjugate development for the future European Solar Telescope. A major limitation is the large field of view presently used for wavefront sensing, leading to uncomfortably large uncertainties in r_0 at 30 km distance.