The ALMA Holography Tower

31 December, 2009 / Read time: 1 minute

Former North American ALMA Project Director Dr. Adrian Russell talks about the shaping of ALMA's telescope dishes.

Every ALMA telescope dish was precision-shaped on site to ensure that its reflection surface is a near-perfect parabola. We use holography towers to read the bumps on a telescope dish, and then engineers make adjustments by hand to reshape the surface.

By pointing the antennas at one of the two 50-meter high holography towers at the OSF, a special holography receiver on the antennas can help create a map of the surface of the antenna to identify imperfections.

Throughout the life of the observatory, an antenna will be brought down from the high site and re-calibrated in this way about every five years

Credits: National Radio Astronomy Observatory (NRAO)