The SolarSIMs have been developed to provide the solar and research communities with a robust, reliable and affordable method to acquire continuous, accurate measurements of solar spectral irradiance.
The SolarSIM technology is based upon the insight that sunlight is a constrained light source. The extraterrestrial solar spectrum is known, through decades of measurement, to an extremely high level of accuracy and there are only a handful of major phenomena (six) that impact the sun’s spectrum as it passes through our atmosphere:
- Rayleigh scattering
- Precipitable water vapour absorption
- Aerosol absorption
- Ozone absorption
- Atmospheric gas absorption (N2, O2, Ar, CO2, CH4, etc.)
- Trace gas absorption (SO2, NO2)
The SolarSIM-D2 uses silicon photodiodes coupled with narrow-band pass filters to make precise measurements of absolute irradiance at six specific, narrow bands within the solar spectrum. This data is then applied within the SolarSIM’s proprietary algorithms to quantify the spectral impact of atmospheric aerosols, ozone and water vapour. The spectral impact of the remaining phenomena (Rayleigh scattering, atmospheric and trace gas absorption) are highly calculable and accurately constrained by the SolarSIMs onboard measurements of ambient temperature and pressure.
This approach enables the SolarSIM-D2 to generate highly accurate, high-resolution solar spectra, over the full 280-4000mn wavelength range.