1. THIRTY METER TELESCOPE : SSA
The primary mirror (M1) of the Thirty Meter Telescope (TMT) is comprised of 492 hexagonal mirror segments. These segments need to be maintained at the required surface accuracy and stability, against structural deformations caused by temperature, gravity, wind and seismic vibrations. Each mirror segment which is 1.44 meter across corners will be supported by a complex mirror segment support assembly (SSA). The TMT SSA is  designed to provide axial as well as radial support to the mirror segments.  It uses 27 point whiffletree for the axial support and a centrally located Invar diaphragm which take care of radial load of the mirror segment. SSA also features with active warping harness, allows thin mirror to be warped. Two different Indian companies, Avasarala Technlogies Limited in Bangalore and Godrej Industries Limited Mumbai have been awarded a contract to supply few prototype SSA.
Telescope and Mount
Primary Segment Assembly (PSA)
Primary Mirror
30m Diameter, 60m ROC,
492 Segments, 1.44mx45mm
SSA Attached to Mirror, Actuator & Mirror Cell
SSA Assembled at ITCC, Bangalore
Components of SSA made by Indian companies
Central Diaphragm
Material – Invar 36
Machining to uniform thickness of 0.3mm with close tolerances (+/ mm).
Ensuring Flatness & position of tabbed holes after slitting operation.
Lateral Guide Flexure
Material – Al 7075 T651
Machining to uniform thickness of 0.725mm with close tolerances (+/ mm).
Ensuring Flatness & controlling warpage.
Vacuum gauge fixture
Central diaphragm
Lateral Guide Flexure Clamping Fixture
Lateral Guide Flexure
Tower Assembly
Material – Al 6061
Machining of critical dimensions to close tolerances.
Ensuring Position of critical dimensions to close tolerances with respect to multiple datum surfaces (Dia / Hole on the Tower).
Repeatability of Inspection values on CMM.
Moving Frame Assembly Machined
Material – Al 6061 Alloy, Extrusion & Casting.
Machining of critical dimensions to close tolerances.
Ensuring Position of critical dimensions to close tolerances with respect to multiple datum surfaces.
Repeatability of Inspection values on CMM.
Mirror Simulator
Material – Al 6061
Machining of spherical radius (concave/convex surface).
Machining of all the features (Whiffletree holes, pockets, side face holes etc.) with respect to Z=0 optical surface vertex.
Ensuring Position to close tolerances with respect to multiple datum surfaces.
Method of Inspection & Repeatability of Inspection values on CMM/Touch Probes/Laser.
Moving Frame Assembly Machined
Tower Assembly
Fixed Frame Assembly
Material – Al 6061
Machining of critical dimensions to close tolerances.
Ensuring Position of critical dimensions to close tolerances with respect to multiple datum surfaces.
Controlling Stitch-weld dimensions as per drawing.
Repeatability of Inspection values on CMM.
Mirror Rod Flexure
Material – 17-4 PH H1150
Ensuring Position of dimensions to close tolerances as per drawing.
Mirror Simulator
Mirror Rod Flexure
Fixed Frame Assembly