  The French-Italian interferometric gravitational wave detector VIRGO is
currently being commissioned. Its principal instrument is a Michelson laser
interferometer with 3 km long optical cavities in the arms and a
power-recycling mirror. The interferometer resides in an ultra-high vacuum
system and the mirrors are suspended from multistage pendulums for seismic
isolation.
  This type of laser interferometer reaches its maximum sensitivity only when
the optical setup is held actively very accurately at a defined operating
point: control systems using the precise interferometer signals stabilise the
longitudinal and angular positions of the optical component. This paper gives
an overview of the control system for the angular degrees of freedom; we
present the current status of the system and report the first experimental
demonstration of the Anderson technique on a large-scale interferometer.
