Brazilian Tunable Filter Imager (BTFI) Preliminary Design Review (PDR)‏ USP-IAG Universidade de São Paulo 18-19th June 2008 FEA Analysis Summary Version 1.0

Mechanical Structure Compliant with Space Envelope Weight limit tbc through FEA analysis – Current analysis is BTFI structure alone SAM with BTFI + SIFS (or SAMI) loads Full FEA of SAM + BTFI Modular structure – Welded Al tubes with bolted connections – Al plate covers – Open structure – to let the light through! – Stiff bottom structure – interface to SAM or ISB port

Structural Model Aluminium Plate Aluminium Square Tube Steel Shaft Bottom Structure

Loads (Assume Connection to Rigid Body at 10  C) FP I (30kg) FP P (30kg) iBTF (19.5kg) Detectors (7.5kg) [0 th & 1 st order] Cameras + folds (3.2kg) [0 th & 1 st Order]

IR-Direct + SAM port configurations (6 cardinal-point orientations) ISB SAM

Flexure map (maximum flexure measures) 88.64μm μm 88.64μm μm 63.28μm 63.39μm ISB SAM

1 st significant eigen modes for complete structure Frequency [Hz]Mode ShapeMax displacement [mm] Ty - Rx Tx - Ry Tz - Rz Tx – Tz - Rz Tx - Tz5.55 To quote Santoro “Nothing to worry about. Actually, the results show that the preliminary mechanical structure is pretty stiff, thanks to Rene's experience.”

Conclusions Fernando Santoro: Bottom structure very stiff and can be light weighted: – Corner needs reinforcement; design/FEA iteration recommended Gravity vector acts in most directions of instrument: – symmetric mechanical bottom structure recommended by adding “A-struts”; When possible, a truss-like structural frame should be used: – extra weight compensated by reducing the thickness of some components; Light-weighting of FP modules? – Larger stainless steel rails, perhaps Rene + KT: Results quite encouraging – Major flexure in direction of camera focus Very insensitive – Major sensitivity is rotation of FPs (90µm tolerance) Structure performance within tolerance – thicken FP rails to be sure? – Real-life performance improved by inclusion of outer shell