Scientific Sponsorship Statement - (HKU.SSS)

Station:The University of Hong Kong, since 1995.
	Model 501, UV-Biometer for UVB, from Solar Light Co.
	Model 501-UVA, UV-Biometer for UVA, from Solar Light Co.
	Microtops II, sunphotometer for total ozone column, from Solar Light Co.
	Spectroradiometer comprising of a double monochromator for solar spectrum, from 
International Light Inc.

	The station is located on the roof top of one of the highest buildings in the University Campus.  
The 501 UV-Biometer responses to 290 - 320 nm UV radiation and measures its biological effect 
through a sensor with a response curve that parallel the sunburn action spectrum (CIE) for the skin [1].  
It is temperature stabilized (< 1% from 25 oC) and has a near cosine response (within 5% for incident 
angle < 60o).  The recorded signal is integrated every 15 minutes and converted to give the global 
erythemal in MEDs h-1.  The 501-UVA is similar to 501 except in the spectral response, which is 320 
- 400 nm.  Output is given every 15 minutes in mW cm-2.  Accuracy for both biometers is claimed to 
fall within +- 5% for daily total.

	Calibration is required only once a year for the two biometers.  This is done by using a transfer 
calibration standard 501 detector, which is NIST traceable, obtained from the Solar Light Co.  Routine 
maintenance includes cleaning the quartz domes of the biometers, checking recorded data; moisture 
indicator; detector mounting and leveling.

	The Microtops II is a hand held instrument for measuring total ozone column.  Solar UV 
radiation at 3 wavelengths (300.0 nm, 305.5 nm and 312.5 nm) are measured.  The ratio in intensity 
between the first two wavelengths is an indication of the amount of ozone between the observer and 
the Sun.  The 3rd wavelength corrects for particulate scattering and stray light.  The precipitable water 
column is also determined by measuring two additional wavelengths at 940 nm and 1020 nm [2].

	The Microtops II can only operate when the Sun is visible.  Measurements are normally done 
near the noon when the Sun is brightest.  Calibration is done through participating in intercomparison 
programs occasionally.

	The spectroradiometer is used only occasionally for measuring the solar spectrum.  Spectral 
calibration is done regularly by a Hg(Ar) spectral calibration lamp while the spectral responsivity is 
calibrated by using a 30 W deuterium source and a 45 W quartz tungsten halogen lamp, both from 
Oriel Instruments and both are NIST traceable.

REFERENCES

[1]	Morys, M.; and Berger, D. "The Accurate Measurement of Biologically Effective Ultraviolet 
Radiation" Proceedings, International Symposium on High Latitude Optics, Tromso, Norway, 
July 1993.

[2]	Morys, M.; Mims, F.M. and Anderson, S. "Microtops II portable ozonometer - design, 
calibration and performance", 12th International Congress on Photobiology, Vienna, 1996.




John K.C. Leung
Radioisotope Unit, The University of Hong Kong

July 1999.