Abstract
Indoor airflow is a major source of uncertainty in interferometric testing of large optics, yet quantitative criteria for identifying conditions that support repeatable measurements remain limited. We simultaneously measured the INTENSE-based effective Fried parameter (
r
0
) and interferometric root-mean-square wavefront error (RMS WFE) of a 1 m-class mirror under four airflow conditions involving forced airflow, local mixing, and no fan operation. For each condition, the primary analysis used ten 1-min measurements, with five additional 1-min measurements used for reproducibility assessment. Session-mean effective
r
0
alone did not consistently indicate repeatability: the condition with the largest mean effective
r
0
differed between sessions, whereas the combined forced-airflow and local-mixing condition exhibited the smallest observed repeat-measurement fluctuations in both effective
r
0
and RMS WFE. Normalized effective-
r
0
fluctuation was used as a scale-adjusted descriptor for intersession comparison, whereas absolute fluctuation showed a stronger exploratory association with RMS WFE fluctuation. Analyses of low-order Zernike modes and temporal power spectral density provided complementary modal and spectral information. Within the present facility and sampled time scales, these results suggest that the fluctuation of effective
r
0
may complement its mean value and the corresponding RMS WFE statistics when evaluating measurement repeatability.