A method of operating an optical icing conditions sensor for an aircraft, the method comprising: transmitting , with a transmitter , a light beam having a wavelength through an optical window of the aircraft at a transmitting angle, wherein the light beam illuminates an illumination volume and the transmitter is oriented along a transmitter path (T) which extends along the transmitting angle; receiving , with a receiver array , light over a range of receiving angles along a receiver array path (R), wherein the receiver array is oriented along the receiver array path and receives the light at the wavelength along the receiver array path, wherein the receiver array is configured to receive the light having the wavelength over a receiver array field of view, and the receiver array field of view overlaps with the illumination volume at a predetermined distance, wherein the receiver array path and the transmitter path intersect at a distance from an outer surface of the optical window; measuring , with a controller, an intensity of the light received by the receiver array; comparing , with the controller, the intensity to a threshold value; determining , with the controller, that a cloud is present if the intensity is greater than the threshold value; calculating , with the controller, scattering profile data of the light received by the receiver array if a cloud is determined to be present, wherein the scattering profile data includes an angle of a scattering intensity peak within the range of receiving angles and a breadth of the scattering intensity peak; and estimating , with the controller, a representative droplet size within the cloud using the scattering profile data. transmitting , with a transmitter , a light beam having a wavelength through an optical window of the aircraft at a transmitting angle, wherein the light beam illuminates an illumination volume and the transmitter is oriented along a transmitter path (T) which extends along the transmitting angle; receiving , with a receiver array , light over a range of receiving angles along a receiver array path (R), wherein the receiver array is oriented along the receiver array path and receives the light at the wavelength along the receiver array path, wherein the receiver array is configured to receive the light having the wavelength over a receiver array field of view, and the receiver array field of view overlaps with the illumination volume at a predetermined distance, wherein the receiver array path and the transmitter path intersect at a distance from an outer surface of the optical window; measuring , with a controller, an intensity of the light received by the receiver array; comparing , with the controller, the intensity to a threshold value; determining , with the controller, that a cloud is present if the intensity is greater than the threshold value; calculating , with the controller, scattering profile data of the light received by the receiver array if a cloud is determined to be present, wherein the scattering profile data includes an angle of a scattering intensity peak within the range of receiving angles and a breadth of the scattering intensity peak; and estimating , with the controller, a representative droplet size within the cloud using the scattering profile data. <EOS>