FLAO Alignment Procedures G. Brusa, S. Esposito FLAO system external review, Florence, 30/31 March 2009

2 FLAO 09 Alignment Procedures Test Tower alignment of M2 Unit, Retro- Reflector and W Unit. Telescope alignment of M2 Unit, M3, Retro- Reflector and W Unit, for calibration purposes. Telescope alignment of W Unit, with de-rotator axis.

FLAO system external review, Florence, 30/31 March Test Tower Setup ~13.7 meters of optical (vertical) path. Two conjugate configuration M2 Unit at top with dummy telescope hub. Retro-reflector structure mounted on hub. AGW Unit mounted at bottom of tower.

FLAO system external review, Florence, 30/31 March Part A - Description M2 Unit, i.e. adaptive secondary, hexapod and hub. Retro-reflector support and optics. F/1 parabola flat

FLAO system external review, Florence, 30/31 March Part B - Description IR camera dichroic Beam Splitter Internal Calibration Source WFS board

FLAO system external review, Florence, 30/31 March Optical Setup Part A Part B

FLAO system external review, Florence, 30/31 March Alignment Goals The two optical axes (Part A and B) have one point in common: the ICS focal point. The two optical axes have a maximum angular offset of <2 arc-min. Limited by de-rotator sensitivity to angular misalignment. The total wave-front aberration is not significantly larger than the baseline for the AS figure (120nm RMS). Limited by wave-front sensor range.

FLAO system external review, Florence, 30/31 March Alignment Preliminary Requirements The alignment of the retro-reflector structure with the AS and the RR has been already carried out during the optical characterization of the AS [AD17]. So that we can rule out large errors in the positioning of the various component of Part A (in particular the retro-reflector). The W-unit should be internally aligned, using the optical axis of the first lens of the triplet as a reference axis [AD in preparation]. So that we can rule out large errors in the positioning of the various component of Part B. The AS figure error (WF, single pass) should be ~60nm RMS (flattening baseline) [AD2]. To bring it within the WFS optical aberration range.

FLAO system external review, Florence, 30/31 March Step 0 - Initial configuration RR positioning error: +/- 2mm ICS position: manually adj. Hexapod adjustment. Translation: +/- 5mm Vertex rotation: +/- 15’ WFS board adj. Translation: ~100mm Tilt: ~15 arcmin ICS

FLAO system external review, Florence, 30/31 March Step 1 – Auto-collimation Step 1 is achieved by tilting the AS unit around its vertex (using the Hexapod) until the AS axis is bisecting the angle IRS-VM2-RR. Vertex rotation RR-ICS axis ICS

FLAO system external review, Florence, 30/31 March Step 2 – Off axis correction Step 2 is achieved by tilting the AS unit around its center of curvature (using the Hexapod) until the AS axis is aligned with the IRS-RR direction. RR-ICS axis rotation ICS

FLAO system external review, Florence, 30/31 March Step 3 – WFS pupil centering Step 3 can be achieved by tilting the WFS board with respect to its translation stages. ICS RR-ICS axis

FLAO system external review, Florence, 30/31 March Summary 1.We have identified an alignment strategy that provides: 1.Minimization of the off-axis aberration of M2. 2.Alignment of the WFS Unit pupil image. 2.At the test tower the optical axis is identified for by the location of the ICS. 3.At the telescope the identified axis will need to be the de-rotator mechanical axis. The strategy will need to be updated.