Satellite laser ranging using pseudonoise code modulated laser diodes

Techniques for satellite laser ranging have historically employed high-energy pulsed lasers as the optical transmitter. The output power currently available from laser diodes and laser diode arrays makes them a viable alternative to the pulsed laser for ranging applications. We examine the modulation of a laser diode by a pseudonoise code which produces a cw ranging signal with equivalent average power to that of current pulsed systems. A maximum-likelihood receiver for estimating signal arrival time using ideal rectangular pulses is shown to be a correlation receiver. A Uramer-Rao bound on the range error is derived for a ranging system with Gaussian code pulses and a correlation receiver. Ranging performance is evaluated for a single cubecorner retroreflector and a tilted flat diffuse target. It is shown that range accuracy of the order of 1 cm is feasible.