Instrumentation

Top of SUV-100 spectroradiometer at Palmer Station

With the exception of Summit, each NSF UV network site is equipped with a scanning SUV-100 spectroradiometer manufactured by Biospherical Instruments. The instrument measures global spectral irradiance between 280 and 600 nm with a resolution of 1 nm. It is designed for permanent installation and continuous operation in harsh climates. The system is fully-automated and needs operator attention only for periodic manual calibrations and operational checks.

The SUV-100 is based on a temperature-stabilized, scanning double-monochromator coupled to a photomultiplier tube (PMT) detector. A Teflon diffuser serves as irradiance collector and is heated to minimize ice and snow buildup. Lamps for automated wavelength and intensity stability checks are integrated in the system. Data acquisition is performed with a PC and data are automatically transferred to Biospherical Instruments via the Internet. A cutaway diagram of the SUV-100 can be found here. The system is calibrated every two weeks with irradiance standard lamps, which are mounted above the irradiance collector in a specially designed lamp housing. More information on the SUV-100 including specifications can be found in Section 2.1. of Network Operations Reports (PDF file).
 

SUV-150B spectroradiometers

SUV-150B installation at Summit. The instrument's collector is in the center of the box-like structure. GUV-511 and PSP radiometers are shown in the background.

The SUV-150B is a newly developed scanning spectro-radiometer, designed and built by Biospherical Instruments. Like SUV-100 systems, it measures global spectral irradiance between 280 and 600 nm. The spectral resolution is 0.63 nm. The instrument is fully automated and weatherproofed for use in extreme conditions, and is currently deployed at Summit, Greenland.

The entrance optics of the SUV-150B consist of a Teflon diffuser covering the entrance port of a baffled integrating sphere. The sphere’s exit port is coupled with fiber optics to a scanning 150 mm f/4.4 Czerny Turner double monochromator. The two gratings of the monochromator are independently positioned by micro-stepping motors. High-resolution optical encoders provide active-feedback motor position control. The monochromator’s exit port is coupled to a bialkali PMT. All parts of the instrument are temperature stabilized to within ±1°C by a thermoelectric heater/cooler. A mercury lamp and a tungsten-halogen lamp are integral to the system and are used for daily wavelength and responsivity checks. Absolute calibrations are performed every two weeks with a similar setup as used for the SUV-100.
 

GUV-511 and GUV-541 multi-channel radiometers

GUV-511 radiometer.

GUV radiometers are moderate-bandwidth filter instrument, which measure spectral irradiance at 305, 320, 340, and 380 nm with a bandwidth of approximately 10 nm. The GUV-511 measures in addition Photosynthetically Active Radiation (PAR). The GUV-541 instrument has an additional channel at 313 nm. Both instruments were designed and manufactured by Biospherical Instruments. From the instrument's irradiance measurements a variety of data products can be calculated, including spectral integrals (e.g. UV-B or UV-A), UV dose-rates (e.g. erythemal irradiance, the UV Index, DNA damaging UV), and total ozone. A detailed description of the instruments and their calibration procedure can be found here (PDF file).
 

Eppley PSP and TUVR radiometers