Systems and methods for transmit and receive aperture alignment in optical ground stations using beam direction feedback

A method for aligning a transmit aperture and a receive aperture of an optical ground station, comprising:

• transmitting an optical beam from a laser source to a beamsplitter;
• directing a first portion of the optical beam from the beamsplitter to a mirror;
• directing a second portion of the optical beam from the beamsplitter to a retroreflector;
• deflecting the first portion of the optical beam with the mirror and relaying the deflected first portion of the optical beam through an optical system to a transmit aperture;
• reflecting the second portion of the optical beam with the retroreflector parallel to an incident beam and returning the reflected second portion of the optical beam to the beamsplitter;
• converting an angular displacement of the reflected second portion of the optical beam into a lateral displacement spot with a lens;
• detecting the lateral displacement spot with a camera to determine a direction of an output optical beam;
• and
• adjusting an angular deflection of the mirror based on feedback from the camera to align the transmit aperture and the receive aperture.

A system for optical ground station transmitting and receiving aperture alignment, comprising:

• a laser source configured to generate a beacon optical beam;
• a beamsplitter configured to divide the beacon optical beam into a transmit portion and a reference portion;
• a tip-tilt mirror configured to steer the transmit portion of the beacon optical beam;
• an optical relay system configured to direct the steered transmit portion of the beacon optical beam through a transmit aperture;
• a retroreflector prism configured to reflect the reference portion of the beacon optical beam parallel to an incident beam and return the reflected reference portion of the beacon optical beam through the beamsplitter;
• a lens configured to convert angular displacement of the reflected reference portion of the beacon optical beam into a lateral displacement at an image plane;
• a camera positioned at the image plane and configured to detect both the lateral displacement and an image of a distant object;
• and
• a controller configured to:
• determine a pointing direction of the beacon optical beam based on the lateral displacement;
• adjust the tip-tilt mirror to direct the beacon optical beam toward the distant object;
• and
• align an optical axis of the transmit aperture and an optical axis of the receive aperture by referencing the distant object.