Jacob W. M. Baars obtained the Ir- and Dr. Ir.-degrees in physics from the Technical University Delft in 1963 and 1970, respectively. After a three year stint at the National Radio Astronomy Observatory (USA) he joined the Netherlands Foundation for Radio Astronomy in 1966. There he participated in the construction and commissioning of the Westerbork Synthesis Radio Telescope and directed its operation from 1972. Upon moving to the Max-Planck-Institut für Radioastronomie in Bonn in 1975, he was project manager of two advanced millimeter wave radio telescope projects – the IRAM mm-telescope on Pico Veleta, Spain and the Heinrich Hertz Telescope on Mt. Graham, Arizona, USA. He served as Project Scientist during the definition and design phase of the Large Millimeter Telescope of Mexico/University of Massachusetts. In 1999 he joined the ALMA group at the European Southern Observatory in Garching, where he performed tasks in management, system engineering and in particular the design, construction and evaluation of two prototype submillimeter radio telescopes. Since his retirement he has acted as consultant to radio telescope projects and participated in project review committees, in particular the Square Kilometre Array. Hans Jürgen Kärcher obtained the Dipl.Ing. and Dr.-Ing. degrees in structural and mechanical engineering from the Technical University in Darmstadt in 1968 and 1974, respectively. He joined MAN Gustavsburg, (now MT Mechatronics) in 1974, initially as system engineer for telescopes and communication antennas. From 1986 up to retirement in 2006 he was head of research and development programs. From 2006 to now he is consultant for telescope mechanics, associated with MT Mechatronics, Mainz. He was project manager and/or lead system engineer for about 40 major telescope projects, optical as well as radio. Highlights were e.g. the 30m Millimeter Radio Telescope MRT IRAM in Spain, the 50m Large Millimeter Telescope LMT/GTM in Mexico, the 2.7mStratospheric Observatory for Infrared Astronomy SOFIA in the US, and the 4m Advanced Solar Telescope ATST/DKIST on Maui, Hawaii.