The base of each 12-meter Vertex telescope arrives from Kilgore, Texas already assembled. It is hoisted by crane to an upright position and driven into the giant Vertex building to be joined to a dish made by VertexRSI in Germany.

The pieces of the telescope's dish arrive like slices of pie. Each segment has a support backbone topped with a dish panel.

Notice all of the small dark pins sticking out of the dish panels. These targets help engineers make a 3-D map of any bumps in the shape of the dish. Technicians tighten or loosen corner bolts on the tiers to smooth out the dish shape. When they have done the best they can, the technicians pull off the pins, pop in a special camera near the telescope's focus, and start the next round of smoothing.

A light on a tall tower shines on the dish, and the parabola bowl shape of the dish bounces the light right up to the camera. It creates a picture of how well the dish reflected that light, showing all of the smaller bumps and dips on its surface. These also can be corrected to create a parabola shape.

Engineers will carry out more routine checks throughout the telescope's half century of operating life.

Join Adrian Russell for a look at one of ALMA's two holography towers.