Air-data system with background light detection using a background rejection filter

A method for measuring air data of an atmosphere, the method comprising:

• projecting, via a light projector, a beam of light into a projection volume of an atmosphere;
• receiving, via an optical receiver, light from a reception volume of the atmosphere, the reception volume and the projection volume forming an intersection volume, wherein the light received by the optical receiver includes:
• i) a Doppler-shifted reflected portion of the projected beam backscattered by the atmosphere from within the intersection volume;
• and ii) a background-light portion from within the reception volume;
• separating, via a background-light rejection filter, the light received by the optical receiver into a beam sampling portion and a complementary non-beam portion, the beam sampling portion having band-pass wavelengths that include the Doppler-shifted reflected portion and a band-pass limited amount of background light, the complementary non-beam portion including background light of wavelengths outside of the band-pass wavelengths;
• estimating, via an air-data processor, the limited portion of the background light included in the beam sampling portion based on the non-beam sampling portion;
• excising from the beam sampling portion, via an air-data processor, the band-pass limited amount of the background light included in the beam sampling portion as estimated, thereby determining the Doppler-shifted reflected portion received by the optical receiver;
• and
• calculating, via an air-data processor, metrics of the air data based on the Doppler-shifted reflected portion as determined.