Long-term stability of deformable mirrors (DM) is a critical performancerequirement for instruments requiring open-loop corrections. The effects oftemperature changes in the DM performance are equally critical for suchinstruments. This paper investigates the long-term stability of three differentIris AO PTT111 DMs that were calibrated at different times ranging from 13months to nearly 29 months prior to subsequent testing. Performance testingshowed that only a small increase in positioning errors occurred from theinitial calibration date to the test dates. The increases in errors ranged fromas little as 1.38 nm rms after 18 months to 5.68 nm rms after 29 months. Thepaper also studies the effects of small temperature changes, up to 6.2{\deg}Caround room temperature. For three different arrays, the errors ranged from0.62-1.42 nm rms/{\deg}C. Removing the effects of packaging shows that errorsare $\le$0.50 nm rms/{\deg}C. Finally, measured data showed that individualsegments deformed $\le$0.11 nm rms/{\deg}C when heated.
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