Radiometry of the Sun and sky, extension to the IR
I have used the calibrated Sekonic meter to scale measurements made with an Ocean Optics NIRQuest (900 – 2,500nm) spectrometer.
I first did a relative intensity-wavelength calibration of the NIRQuest using a measurement of a quartz-halogen lamp that operates near 3000K. The ratio of the Planck function to the spectrometer counts was then scaled to fit an extinction-corrected spectrum of the solar emission at the Earth.
In this case the intensity (irradiance) calibration is tied to that of the Sekonic meter which, in turn, it tied to a NIST standard.
The description of the spectra in this plot follow the description in the previous post.
The pale grey line is the solar flux outside the atmosphere (from the Hubble calibration database). Although the legend says 'scaled', the scaling factor is unity.
The blue line spectrum is the extinction-corrected solar flux for an airmass of 1.58. The observation was made with a very milky sky and the model used a much lager aerosol value than the measurement in the previous post.
The thick red line shows the Sekonic C-7000 data in the visible and the NIRQuest data in the infrared from 900 - 2,500nm.
The strong absorption bands in the infrared are dominated by telluric (formed in the Earht's atmosphere) water vapour but also include contributions from carbon dioxide, methane and the O2*O2 and O2*N2 dimers (the dip just above 1,250nm).
O2*O2 collisionally induced absorptions (CIA) also appear prominently in the visible spectrum when the Sun is low in the sky and are formed mostly in the low atmosphere (see the comment below).
[2020-03-30, Ozone changed from 2 to 1.6]
Radiometry of the Sun and sky, extension to the IR
I have used the calibrated Sekonic meter to scale measurements made with an Ocean Optics NIRQuest (900 – 2,500nm) spectrometer.
I first did a relative intensity-wavelength calibration of the NIRQuest using a measurement of a quartz-halogen lamp that operates near 3000K. The ratio of the Planck function to the spectrometer counts was then scaled to fit an extinction-corrected spectrum of the solar emission at the Earth.
In this case the intensity (irradiance) calibration is tied to that of the Sekonic meter which, in turn, it tied to a NIST standard.
The description of the spectra in this plot follow the description in the previous post.
The pale grey line is the solar flux outside the atmosphere (from the Hubble calibration database). Although the legend says 'scaled', the scaling factor is unity.
The blue line spectrum is the extinction-corrected solar flux for an airmass of 1.58. The observation was made with a very milky sky and the model used a much lager aerosol value than the measurement in the previous post.
The thick red line shows the Sekonic C-7000 data in the visible and the NIRQuest data in the infrared from 900 - 2,500nm.
The strong absorption bands in the infrared are dominated by telluric (formed in the Earht's atmosphere) water vapour but also include contributions from carbon dioxide, methane and the O2*O2 and O2*N2 dimers (the dip just above 1,250nm).
O2*O2 collisionally induced absorptions (CIA) also appear prominently in the visible spectrum when the Sun is low in the sky and are formed mostly in the low atmosphere (see the comment below).
[2020-03-30, Ozone changed from 2 to 1.6]