Steerable windowed enclosures

A gyro-stabilized mechanism that is to be carried on a vehicle, such as a helicopter, is provided with a protective enclosure consisting of a dome, usually of glass fibre reinforced plastic. The dome must be provided with a window transparent to the radiation involved, and this must be steered with the mechanism so that they remain in register with one another. Prior art structures employ elongated windows of sufficiently large size to accommodate the tilting and rolling of the mechanism, while pan movements are accommodated by rotating the entire dome. The invention provides a structure employing a small window that can be steered or slaved with the mechanism by rotation of the part of the dome including the window relative to the other part, which has the pan or yaw rotation motor connected to it. This rotation between the dome parts takes place in a skew plane disposed at as small a skew angle to the vertical as is possible, the compensation for the resulting transverse movement of the window being effected by a programmed rotation of the dome about the pan axis. Optically flat glass can then be used for the window, it can be coated to reduce reflections, etc, and it can also be wiped in operation to remove moisture. A broadcast antenna can be mounted on the part of the dome out of the line-of-sight of the apparatus.