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===== DS =====
=== Direct Sun Ozone Observation ===
DS results in an O3 observation being taken using the direct sun as a radiation source. The Brewer Zenith Prism and Azimuth Tracker are oriented toward the sun, the Iris is closed, FW#1 is rotated to the Ground Quartz Disk (position 1), and FW#2 is adjusted for maximum intensity (starting from position 2) without overdriving the PMT detector. Data is recorded on disk and is printed as previously determined by PN, PD, and PF commands.\\

A DS observation consists of five sets of 20 cycles of the slit mask (a measurement), each cycle taking a reading for 2*0.14 seconds on each wavelength. Intensity data for six wavelengths, and the dark count, is recorded for each of the five measurements. The Azimuth and Zenith positions are updated after each measurement.
After each measurement O3 are calculated. After the fifth measurement all data is processed, resulting in a single summary set for the total observation.\\

As a safety feature to prevent damage to the detector, the measurement may terminate if, as a result of varying cloud conditions, FW#2 has initially been set to a low attenuation value and clouds suddenly move out of the field of view. A DS measurement takes slightly more than three minutes to complete.