Combined laser altimeter and ground velocity measurement apparatus

Laser-based apparatus for generating signals for use in determining both altitude and ground velocity of an aircraft, said apparatus comprising:

• a laser source for emitting pulsed laser beams substantially at a predetermined wavelength over a first optical path;
• a plurality of first optical elements for directing said laser beams from said first optical path to a second optical path which exits said first optical elements;
• a plurality of second optical elements configured to form a telescope with a predetermined field of view, said second optical path and telescope field of view being fixedly co-aligned;
• said telescope for receiving Doppler wavelength shifted reflections of said pulsed laser beams within the field of view thereof and directing said received reflections substantially over a third optical path;
• an optical filter element disposed in said third optical path for separating the reflections of said third optical path into first and second portions that are dependent on the Doppler wavelength shift of said reflections;
• and
• light detection means for receiving said first and second portions and generating first and second signals representative of said first and second portions, respectively.

A distributed laser-based system for use on-board an aircraft for determining both altitude and ground velocity of said aircraft, said system comprising:

• at least three laser-based measurement apparatus for disposition at different locations on said aircraft, each said apparatus comprising:
• a laser source for emitting pulsed laser beams substantially at a predetermined wavelength over a first optical path;
• a plurality of first optical elements for directing said laser beams from said first optical path to a second optical path which exits said first optical elements;
• a plurality of second optical elements configured to form a telescope with a predetermined field of view, said second optical path and telescope field of view being fixedly co-aligned;
• said telescope for receiving Doppler wavelength shifted reflections of said pulsed laser beams within the field of view thereof and directing said received reflections substantially over a third optical path;
• an optical filter element disposed in said third optical path for separating the reflections of said third optical path into first and second portions that are dependent on the Doppler wavelength shift of said reflections;
• and
• light detection means for receiving said first and second portions and generating first and second signals representative of said first and second portions, respectively;
• each said laser-based apparatus configurable to direct its co-aligned second optical path and telescope field of view from said aircraft to a different ground position from the other laser-based apparatus;
• and
• a processing unit for receiving and processing said first and second signals from said at least three laser-based apparatus to determine both said altitude and ground velocity of said aircraft.