Dr Barbara Brooks

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Instrument Support Level 3
Instrument Support Level

Instrument Support Level 3

Manufacturer & Model

Spectrafy, SolarSIM-D2

Daily Facility Charge

Not Applicable


Calendar 2:
Spectrafy Sun Photometer

Spectrafy Sun Photometer

The SolarSIM-D2 represents a bold new approach to solar and atmospheric measurement. It uses simple, rugged hardware and ground-breaking software to accurately resolve full-range and custom range DNI, as well as direct solar spectral irradiance, atmospheric AOD, ozone and precipitable water vapour – all in one small, easy-to-deploy, affordable package.

The SolarSIM-D2 enables this huge leap forward in functionality by deploying silicon photodiodes, coupled with hard-coated optical filters to measure the direct solar spectrum in several narrow wavelength bands. The SolarSIM-D2’s proprietary software then uses these measurements to resolve the complete solar spectrum and DNI, in addition to major atmospheric processes, such as air mass, Rayleigh scattering, aerosol optical depth, ozone-layer thickness, and precipitable water vapour.

The SolarSIM-D2 offers ultimate flexibility. It can be deployed with any one or more of its measurement capabilities engaged, and additional capabilities can be added at any point in the future via a simple software upgrade – with no additional hardware required.

The SolarSIM-D2 provides a versatile, low-cost, low-power tool for accurately determining DNI, the direct solar spectrum and major atmospheric constituents for on-site solar resource assessment, meteorological monitoring, PV or CSP performance prediction and weather or climate modelling.

The SolarSIM-D2 is a hugely versatile device that can provide the function of a pyrheliometer, a spectroradiometer, a sunphotometer, and an ozone spectrophotometer, all in one. As a result, the SolarSIM-D2 can provide an unparalleled quantity and quality of data – up to 14,000 data points per timestamp! Your SolarSIM-D2 can be configured to deliver any or all of the following:

Direct Normal Irradiance (DNI)
The SolarSIM-D2 provides an accurate measurement of the direct normal irradiance, under any sky conditions, over the complete 280-4000nm spectral range. The SolarSIM-D2 can also be configured to provide DNI over any custom spectral range.

Direct Spectral Irradiance
The SolarSIM-D2 resolves the direct solar spectral irradiance, under any sky conditions, over the complete spectral range of 280 – 4000nm, with 1nm resolution.

Aerosol Optical Depth
The SolarSIM-D2 provides aerosol optical depth values for each wavelength over the complete 280 – 4000nm range.

Ozone content
The SolarSIM-D2 resolves atmospheric ozone absorption values for each wavelength over the complete wavelength range, in addition to the total ozone layer thickness.

Precipitable Water Vapour
The SolarSIM-D2 resolves atmospheric precipitable water vapour values for each wavelength over the complete wavelength range, in addition to the total column amount.

The SolarSIM-D2 also provides accurate measurements of the ambient temperature and atmospheric pressure.

A sun photometer is an electronic device that measures direct sunlight over a narrow range of wavelengths.

When a sun-photometer is placed somewhere within the earth’s atmosphere, the measured radiance is not equal to the radiance emitted by the sun (i.e. the solar extraterrestrial radiance), because the solar flux is reduced by atmospheric absorption and scattering. Therefore, the measured radiant flux is due to a combination of what is emitted by the sun and the effect of the atmosphere; the link between these quantities is given by Beer’s law.

The atmospheric effect can be removed with Langley extrapolation; this method, therefore, allows measuring the solar extraterrestrial radiance with ground-based measurements. Once the extraterrestrial radiance is known, one can use the sun photometer for studying the atmosphere, and in particular for determining the atmospheric optical depth. Also, if the signal at two or more suitably selected spectral intervals is measured, one can use the information derived for calculating the vertically integrated concentration of selected atmospheric gases, such as water vapour, ozone, etc.

As and when required

Field Data
  • The instrument produces a range of out files and all are text format.
  • The user can download (but not delete) this data from the instrument but it should be noted that this data will not have been quality controlled.
Archive Data