THIRTY METER TELESCOPE LASER TRACKER METROLOGY FIXTURE


APPLICATION:

Scientific research. Ground-based radio telescope.

PREVIOUS LIMITING TECHNOLOGY:

The high precision, low weight, high stiffness and low CTE requirements of these reflector alignment fixtures would normally require a prohibitively expensive solution.

CHALLENGE:

The Thirty Meter Telescope (TMT) requires precision fixtures to align the 492 hexagonal mirror segments that make up the massive 30-meter primary mirror array. Ten fixtures are required to complete the reflector alignment. In addition to high precision and low CTE requirements, aggressive cost containment measures were necessary to meet the program’s budget.

SOLUTION

Rock West used off-the-shelf carbon fiber plate and our ZTE™ (zero coefficient of thermal expansion) Carbon Tubes to engineer an elegant and extremely cost-effective solution. We utilized low-cost assembly fixtures using off-the-shelf ground plates trimmed by a waterjet and off-the-shelf precision positioning towers. We also used environmentally-friendly etch and prime technology for the invar fittings. Tolerances were kept within +/-0.0015” and positional stability was maintained at less than 0.0001” over a 10°C change in temperature.

Image shows a manufacturing environment with two technicians working on the TMT metrology fixture. The structure is placed on a metal platform that is sitting on a granite table and held up by three positioning towers. It is comprised of carbon fiber tubes attached at multiple points by dark metallic fittings.
Image shows the completed TMT metrology fixture on a white surface and background. The structure is comprised of carbon fiber tubes attached at multiple points by dark metallic fittings. The bottom of the structure is a circular carbon fiber sandwich panel, with carbon plate covering the edges of the sandwich structure.
Image shows a closeup of the completed TMT metrology fixture on a white surface and background. The structure is comprised of carbon fiber tubes attached at multiple points by dark metallic fittings. The bottom of the structure is a circular carbon fiber sandwich panel, with carbon plate covering the edges of the sandwich structure.
Image shows the completed TMT metrology fixture on a white surface and background. The detail image shows a connection juncture. Several carbon fiber tubes are bonded to a dark metallic and pointed fitting.
Image shows the completed precision fixture on a white surface and background. The detail image shows a connection juncture. Two carbon fiber tubes are bonded to a carbon sandwich panel structure. The edges of the sandwich panel are covered by carbon fiber paneling.
Image shows the completed TMT metrology fixture on a white surface and background. This detail shows a connection juncture, with four carbon fiber tubes bonded to a dark metallic and pointed fitting. Other tubes and the part of the circular base are in the background.
Image of TMT metrology fixtures lined up on the floor of a manufacturing area. There are two rows of three and the viewer is at eye level to the precision fixtures. The hardware appears as black circular shapes with a hollow center that are attached at three major points to black triangular shapes.
Image of TMT metrology fixtures lined up on the floor of a manufacturing area. There are two rows of three and the viewer is above and looking down towards to the precision fixtures. The hardware appears as black circular shapes with a hollow center that are attached at three major points to black triangular shapes.