As the parts are used to hold the optics, calibration was critical to ensure that the incident light was going to the right place. This was achieved using the Hexagon Global CMM, which checks the holes and positional tolerances of the components in the assembly. The Astronomy Technology Center's second Very Large Telescope (VLT) project is ERIS - Enhanced Resolution Imager and Spectograph - which uses the adaptive optics of the main telescope to remove atmospheric distortions when hunting for planets outside our solar system. "Basically, it takes the twinkle out of the stars. This is achieved with a mirror whose surface shape is adjusted hundreds of times per second. This means that the image quality is incredibly high, without any distortion," says Will Taylor. As a member of an international consortium each producing specific mechanisms, he says the UK ATC's role for ERIS was to build the new diffraction-limited camera system, which was coupled to the optics produced in Italy. Richard Kotlewski explains that some of the camera's parts, made from 6082 aluminum, were produced on their 5-axis Haas VF5 machine tool. "Due to their complexity - the top half is quite thin-walled as we are limited in the weight of this instrument - the programming time for each component was about one day and the machining was two days due to the amount of material removed." He uses EDGECAM's powerful 'wavy roughing' strategy to make deeper cuts with less distortion due to the reduced offset, while still achieving optimum material removal rates. For these components, the Hexagon CMM is used in a different way. Although they don't make all the components for this particular assembly, they are responsible for the entire finished instrument. "We have to check the parts we make, along with parts from other members of the consortium, and make sure everything is precisely aligned." The mechanisms have to be within ten micrometers of each other so that everything fits together. Using the Hexagon CMM ensures this. "This work takes over a week. Each individual mechanism is placed on customizable supports attached to the optical bench. Measurements are taken to determine the center of the mechanism and ensure that it is square and parallel. Shims are made to bring the mechanism into the correct position. The mechanism is then checked again. Only when we are completely satisfied with each individual component do we put them all together and carry out a final visual check. Without the CMM, we wouldn't be able to do this important part of the work." Richard Kotlewski concludes: "It's a real privilege to work on such ground-breaking astronomical projects - I'm creating components that make it possible to study the formation and evolution of galaxies over most of the history of the universe with unprecedented accuracy."