  The Cherenkov Telescope Array (CTA) is the next generation of ground-based
gamma-ray observatory. The observatory will consist of two arrays, one located
in the southern hemisphere (Paranal,Chile) and the other in the northern
hemisphere (Canary Island, Spain), covering the whole sky in the range of
observation. More than 100 telescopes are planned to be in operation for as
long as 30 years, which motivated the development of a continuous condition
monitoring of the individual telescopes. The main goal of the monitoring is to
detect degradation and failures before critical damages occur. Two approaches
are considered: the structure monitoring system, in which the Eigenfrequencies
of the telescope and their damping rates are measured and monitored; and the
drive monitoring, in which the power spectra of rotating components are
measured during telescope movements. The structure monitoring concept system
was applied to the prototype Medium Size telescope (MST) prototype of CTA in
Berlin during late 2018 and in 2019, and the first results are presented here.
The system showed reasonable stability during periods, in which the telescope
structure was unchanged. The system was also capable to detect mechanical
changes, e.g. varying tension in the steel ropes of the camera support
structure. The successful implementation of the structure monitoring system
supports the decision of implementing the system in all future MSTs.
