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Figure 1. Left: the first unit of the adaptive secondary mirror for LBT (LBT672a) in the hub. Right: exploded view of the system.

Figure 1 Left: the first unit of the adaptive secondary mirror for LBT (LBT672a) in the hub. Right: exploded view of the system.

Related Figures (16)

Figure 2. On the top the reference body: the armatures of the capacitive sensor co-located with the actuators are visible. On the bottom the thin shell with magnets glued on its back. Photo by R. Cerisola.
Figure 2. On the top the reference body: the armatures of the capacitive sensor co-located with the actuators are visible. On the bottom the thin shell with magnets glued on its back. Photo by R. Cerisola.
Figure 4. scheme of synchronized interaction matrix acquisition with the 4D technology interferometer
Figure 4. scheme of synchronized interaction matrix acquisition with the 4D technology interferometer
Figure 5. Subset of optically measured mirror bending modes.
Figure 5. Subset of optically measured mirror bending modes.
Figure 6. Noise propagation analysis onto the first 100 Zernike modes.
Figure 6. Noise propagation analysis onto the first 100 Zernike modes.
Figure 7. Flattening wavefront error (i.e. two times the surface error) residuals at different temperature: TO=20°C (left) , T1=10°C (center) and T2=5°C (right). The increasing low-order residuals reducing the temperature are given by the disturbance introduced by the convection (ambient temperature = 20°C)
Figure 7. Flattening wavefront error (i.e. two times the surface error) residuals at different temperature: TO=20°C (left) , T1=10°C (center) and T2=5°C (right). The increasing low-order residuals reducing the temperature are given by the disturbance introduced by the convection (ambient temperature = 20°C)
Figure 8. Interferograms of flattened mirror: comparison between the 3 flattening commands and their application at temperatures different from that of calibration
Figure 8. Interferograms of flattened mirror: comparison between the 3 flattening commands and their application at temperatures different from that of calibration
and the results are reported in Figure 8 showing a drift of about 200 nm rms of the flattening residual with 15°C of temperature variation. The first 10 Zernike modes (Noll ordering) have been removed from the WFE simulating the behavior of active optics on the telescope. The blind application of the flattening command is mostly relevant for seeing limited observations and to provide to AO a suitable initial shape for closing the optical loop. In both cases it is sufficient that the blind application of the flattening command results ina WFE that is negligible with respect to the one introduced by the seeing and in particular to the best expected seeing, resulting in a specification of WFE<200 nm rms, i.e. 1/10 of WEE variance error introduced bv a 0.23 arcsec Figure 9. Subset of optically measured KL modes built as superimposition of mirror bending modes
and the results are reported in Figure 8 showing a drift of about 200 nm rms of the flattening residual with 15°C of temperature variation. The first 10 Zernike modes (Noll ordering) have been removed from the WFE simulating the behavior of active optics on the telescope. The blind application of the flattening command is mostly relevant for seeing limited observations and to provide to AO a suitable initial shape for closing the optical loop. In both cases it is sufficient that the blind application of the flattening command results ina WFE that is negligible with respect to the one introduced by the seeing and in particular to the best expected seeing, resulting in a specification of WFE<200 nm rms, i.e. 1/10 of WEE variance error introduced bv a 0.23 arcsec Figure 9. Subset of optically measured KL modes built as superimposition of mirror bending modes
yending modes measurements described in the previous section to form the KL basis, as described in [9] . We have Somputed a total of 630 modes fitted by the functioning 653 actuators.
yending modes measurements described in the previous section to form the KL basis, as described in [9] . We have Somputed a total of 630 modes fitted by the functioning 653 actuators.
Figure 12. Left: fe) ptical layout of the testing configuration of the ASM at the telescope. Center: Retro-reflecting holder structure mounted at the telescope. Right: temperature controlled box of the vibration-insensitive interferometer provided by LBTO at the back-bent-Gregorian focal station. With respect to the Arcetri Test Tower, the telescope environment showed larger vibrations, but a lower degree of mid- and short-scale convection disturbances, possibly due to the larger scale of the convection cells in the dome. The final result of the flattening procedure is shown in Figure 11 with the same performance in term of residual flattening error
Figure 12. Left: fe) ptical layout of the testing configuration of the ASM at the telescope. Center: Retro-reflecting holder structure mounted at the telescope. Right: temperature controlled box of the vibration-insensitive interferometer provided by LBTO at the back-bent-Gregorian focal station. With respect to the Arcetri Test Tower, the telescope environment showed larger vibrations, but a lower degree of mid- and short-scale convection disturbances, possibly due to the larger scale of the convection cells in the dome. The final result of the flattening procedure is shown in Figure 11 with the same performance in term of residual flattening error
Figure 13. Seeing limited PSF taken during on-sky test in April 2010. The PSF is nicely symmetric without artifacts on the wings as indicator of good behavior of the ASM in this operational mode.
Figure 13. Seeing limited PSF taken during on-sky test in April 2010. The PSF is nicely symmetric without artifacts on the wings as indicator of good behavior of the ASM in this operational mode.
Figure 14. Wind effect. Left panel: wind speed during the test. Center, right panels: mean of actuators position and forces, during the test.
Figure 14. Wind effect. Left panel: wind speed during the test. Center, right panels: mean of actuators position and forces, during the test.
Figure 15. Left panel: wind speed during the test. Right panel: Mean actuators force during the test. The horizontal line is the nominal force value calibrated at the current telescope elevation. The maximum positive delta force detected is 15 mN.
Figure 15. Left panel: wind speed during the test. Right panel: Mean actuators force during the test. The horizontal line is the nominal force value calibrated at the current telescope elevation. The maximum positive delta force detected is 15 mN.
Figure 16. PSF in Adaptive Optics closed loop in H-band. Log scale color table. Right: without shift-and-add (80% SR). Left: with shift-and-add to remove the residual vibration contribution (SR>85%). See text for more informations.
Figure 16. PSF in Adaptive Optics closed loop in H-band. Log scale color table. Right: without shift-and-add (80% SR). Left: with shift-and-add to remove the residual vibration contribution (SR>85%). See text for more informations.
Figure 17. Comparison between diffraction limited PSF profile (red line) and AO corrected PSF (black line). The reported profile section is highlighted in the figure on the right. See text for more informations.
Figure 17. Comparison between diffraction limited PSF profile (red line) and AO corrected PSF (black line). The reported profile section is highlighted in the figure on the right. See text for more informations.
Related topics:
Atmospheric TurbulenceCapacitive Pressure SensorLight adaptation
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