Monitoring mirror reflectance using solar illumination

A system to measure a reflectance of a mirror target that includes at least one curved mirror, the system comprising:

• an irradiance spectrometer;
• a spectrometer actuator configured to control an orientation of the irradiance spectrometer;
• at least one processor to control the irradiance spectrometer and the spectrometer actuator, the at least one processor configured to:
• point foreoptics of the irradiance spectrometer directly at the sun such that the sun is within a field of view of the irradiance spectrometer;
• with the foreoptics of the irradiance spectrometer pointed directly at the sun while the sun is within the field of view of the irradiance spectrometer, obtain a first irradiance measurement with the irradiance spectrometer;
• point the foreoptics of the irradiance spectrometer directly at the mirror target such that a reflection of the sun from the mirror target is within the field of view of the irradiance spectrometer;
• with the foreoptics of the irradiance spectrometer pointed directly at the mirror target while the reflection of the sun from the mirror target is within the field of view of the irradiance spectrometer, obtain a second irradiance measurement with the irradiance spectrometer;
• removing the reflection of the sun from the field of view of the irradiance spectrometer;
• with the foreoptics of the irradiance spectrometer pointed directly at the mirror target while the reflection of the sun is removed from the field of view of the irradiance spectrometer, obtain a third irradiance measurement with the irradiance spectrometer;
• and
• determine a reflectance of the mirror target from the first, second, and third irradiance measurements.

A method for measuring a reflectance of a mirror target that includes at least one curved mirror, the method comprising:

• pointing foreoptics of an irradiance spectrometer directly at the sun such that the sun is within a field of view of the irradiance spectrometer;
• with the foreoptics of the irradiance spectrometer pointed directly at the sun while the sun is within the field of view of the irradiance spectrometer, taking a first irradiance measurement with the irradiance spectrometer, the first irradiance measurement representing a direct solar irradiance;
• pointing the foreoptics of the irradiance spectrometer directly at the mirror target such that a reflection of the sun from the mirror target is within the field of view of the irradiance spectrometer;
• with the foreoptics of the irradiance spectrometer pointed directly at the mirror target while the reflection of the sun from the mirror target is within the field of view of the irradiance spectrometer, taking a second irradiance measurement with the irradiance spectrometer, the second irradiance measurement representing an irradiance from a reflection of the sun from the mirror target plus background irradiance from a reflection of the sky from the mirror target;
• removing the reflection of the sun from the field of view of the irradiance spectrometer;
• with the foreoptics of the irradiance spectrometer pointed directly at the mirror target while the reflection of the sun is removed from the field of view of the irradiance spectrometer, taking a third irradiance measurement with the irradiance spectrometer, the third irradiance measurement representing the background irradiance from the reflection of the sky from the mirror target;
• and
• determining, with at least one processor coupled to the irradiance spectrometer, a reflectance of the mirror target from the first, second, and third irradiance measurements;
• determining, with the at least one processor, that the reflectance of the mirror target is less than a specified reflectance threshold;
• and
• in response to the determination that the reflectance of the mirror target is less than the specified reflectance threshold, automatically generating an alert signal.