Kipp&Zonen Brewer MkIII - Manual (Page 43)

MKIII OPERATOR'S MANUAL 40
FM
Focused Moon Observation
FM results in an O
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observation to be taken with the moon as the radiation source.
The Brewer Zenith Prism and Azimuth Tracker are oriented to the moon, the Iris is opened,
FW#1 is rotated to the position 3, and FW#2 is adjusted for maximum intensity, starting at
position 2.
Data is recorded on disk and is printed as previously determined by PN, PD, and PF
commands. An FM observation consists of five sets of 80 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, from the five measurements is
recorded. The Azimuth and Zenith positions are updated after each measurement.
After each measurement O
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is calculated, and after the final measurement all data is
processed, resulting in a single summary set for the total observation.
An FM measurement takes approximately 15 minutes to complete. Note that FM
observations are not valid for ZA>75° and the message ”Waiting for the Moon to Rise above
ZA=75” may appear prior to this angle condition being met. See also Appendix A .
FMSUM Focus Moon Data Summary
FMSUM results in the daily Summary (S) file being read and a printout of the ‘summary’
results of the day’s FM measurements being made. An entry is also made to the
FMOAVG.nnn file.
The FMSUM command is usually invoked as part of the ED command.
FR
Micrometer Reset
FR performs a reset of the wavelength adjust micrometers. The micrometers are moved to
reference points, and then moved to the operating points as dictated by offset values
contained in the instruments constants file.
The FR command is invoked as part of the RE command, or the operator may manually
send the FR command if the positions of the micrometers are suspect.
The FR command may be used to determine new micrometer offset values, but these values
should only be changed under the supervision of qualified personnel.
FR results are recorded in the average file, MIOAVG.nnn.
See also Appendix A.
FZ Focused Sun Observation
As the sun drops lower in the sky, the high Mu values result in an increasing amount of
scattered radiation in the field of view of a DS observation. The FZ command allows ozone
to be determined at solar angles greater than which can be achieved with a traditional DS.
Scattered radiation is measured by offsetting the solar image by 1 degree from the entrance
slit, and observing radiation in the vicinity of the solar disk. This scattered radiation is then
subtracted from the direct sun result to give a more accurate measure of the direct radiation,
before the Ozone determination is made. This method will give reasonably accurate O
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values to ZA of 85° (Air Mass =8.2) as compared to the DS which has cut-off angles of 70 to
80° (Air Mass 3.2 to 5) without corrections. This is a useful command at high latitudes and is
normally not used where DS readings are available.
For the FZ measurement the iris is closed, FW#1 is set to position 3, and FW#2 is set to
position 5.
The minimum zenith angle at which an FZ may be taken is 73°.
See also DS command.
FZSUM Focused Sun Data Summary
FZSUM command reads the daily Data (B) file and printouts out the ‘summary’ results of the
day’s FZ measurements. The FZSUM command is usually invoked as part of the ED
command.