A device, comprising: an aerial vehicle; and an irradiance sensing device including: a base structure mounted to the aerial vehicle, the base structure including five surfaces (116, 118), and five photo sensors respectively arranged on the surfaces of the base structure and having different orientations with respect to each other, wherein the five photo sensors are configured to simultaneously sense irradiance from a light source, and to output signals indicative of the sensed irradiance, and wherein the device further comprises a processor coupled to the five photo sensors and configured to receive the output signals and to determine a direct component and a scattered component of the sensed irradiance, and an azimuth and a zenith angle of the light source in a sensor body coordinate system based on the orientation of the photo sensors and the sensed irradiance, wherein the direct component and the scattered component of the sensed irradiance, and the azimuth and the zenith angle of the light source are determined by solving at least five non-linear equations formed from a set of at least five independent irradiance measurements, the device further comprising an imaging device mounted to the aerial vehicle, wherein the processor is coupled to the irradiance sensing device and the imaging device, the processor being configured to determine a reflectance of a target based on image information of the target acquired by the imaging device and the determined components of irradiance at the time the image information was acquired, and normalizing or compensating the determined reflectance to account for different irradiance levels at the time of imaging the target. an aerial vehicle; and an irradiance sensing device including: a base structure mounted to the aerial vehicle, the base structure including five surfaces (116, 118), and five photo sensors respectively arranged on the surfaces of the base structure and having different orientations with respect to each other, wherein the five photo sensors are configured to simultaneously sense irradiance from a light source, and to output signals indicative of the sensed irradiance, and wherein the device further comprises a processor coupled to the five photo sensors and configured to receive the output signals and to determine a direct component and a scattered component of the sensed irradiance, and an azimuth and a zenith angle of the light source in a sensor body coordinate system based on the orientation of the photo sensors and the sensed irradiance, wherein the direct component and the scattered component of the sensed irradiance, and the azimuth and the zenith angle of the light source are determined by solving at least five non-linear equations formed from a set of at least five independent irradiance measurements, the device further comprising an imaging device mounted to the aerial vehicle, wherein the processor is coupled to the irradiance sensing device and the imaging device, the processor being configured to determine a reflectance of a target based on image information of the target acquired by the imaging device and the determined components of irradiance at the time the image information was acquired, and normalizing or compensating the determined reflectance to account for different irradiance levels at the time of imaging the target. a base structure mounted to the aerial vehicle, the base structure including five surfaces (116, 118), and five photo sensors respectively arranged on the surfaces of the base structure and having different orientations with respect to each other, wherein the five photo sensors are configured to simultaneously sense irradiance from a light source, and to output signals indicative of the sensed irradiance, and wherein the device further comprises a processor coupled to the five photo sensors and configured to receive the output signals and to determine a direct component and a scattered component of the sensed irradiance, and an azimuth and a zenith angle of the light source in a sensor body coordinate system based on the orientation of the photo sensors and the sensed irradiance, wherein the direct component and the scattered component of the sensed irradiance, and the azimuth and the zenith angle of the light source are determined by solving at least five non-linear equations formed from a set of at least five independent irradiance measurements, the device further comprising an imaging device mounted to the aerial vehicle, wherein the processor is coupled to the irradiance sensing device and the imaging device, the processor being configured to determine a reflectance of a target based on image information of the target acquired by the imaging device and the determined components of irradiance at the time the image information was acquired, and normalizing or compensating the determined reflectance to account for different irradiance levels at the time of imaging the target.