Fiber-Optic Rotary Joint for Passing High-Definition Video

Dryden Flight Research Center, Edwards, California

A video camera has been integrated with a tracking pedestal (see figure) for tracking of aircraft and spacecraft. The camera is of a high-definition (1,280 × 720 pixels), progressive-scan, 60-frame-per-second digital type that conforms to NASA Standard 2818 (Digital Television Standards for NASA, a copy of which can be obtained via the Internet at http://www.hq.nasa.gov/office/cio/ standards/2818.pdf). The camera is mated to a 13.5-to-1,755-mm zoom lens, making it possible to track vehicles at distances up to 100 miles (≈160 km).

The digital video signal, at a data rate of 1.5 Gb/s, is transmitted from the camera via an optical fiber. The signal passes through a fiber-optic rotary joint (FORJ) through the horizontal axis of rotation of the pedestal. The FORJ contains two fiber-optic conductors, each capable of a data rate of 3 Gb/s, that are used to pass high-definition video and camera-control signals. All other power and control signals pass through standard copper slip rings in the pedestal.

The FORJ and the pedestal are commercial products. The pedestal was modified to accept the FORJ. The modification included the fabrication of a yoke assembly to enable rotation of the upper half of the FORJ with the rotation of the upper half of the pedestal. The FORJ was originally produced for use in submersible remotely operated vehicles with rotating manipulator arms. The high-bandwidth digital video signal cannot pass through conventional copper slip rings of the unmodified tracking pedestal. The modification of the tracking pedestal to work with the FORJ makes it possible to use high-definition video for tracking experimental aircraft and spacecraft.