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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 micrometer, and the 'order selection'
filterwheel, FW#3. The micrometer and FW#3 are moved to reference points, and then
moved to their operating positions according to offset values contained in the instruments
constants file. Operating points are different for the Ozone Mode and the NO
The FR command is invoked as part of the RE command, or the operator may manually send
the FR command if the position of the micrometer or FW#3 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
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.
HG
Mercury Wavelength Calibration
HG is used to accurately locate the 302.15 nm line of the Mercury spectrum, and then adjust
the diffraction grating such that the five ozone operational wavelengths fall onto the
appropriate exit slits.
The zenith prism rotates to the test lamps (position 0), the iris is opened, FW#1 is rotated to
the quartz disk (position 1), FW#2 to ND=0 (position 0).
Following the initial set-up and lamp warm-up, the grating is scanned in the forward and
reverse direction and the resulting combined spectrum is compared to a stored spectrum.
Corrections to the micrometer position are made, and if the adjustment required is greater
than 2 steps (.012nm) then the scan is repeated. A test for the presence of Hg lamp
radiation is made prior to the beginning of the scan, and if it is not there, an FR test is done to
reposition the micrometers to pre-set initialisation values and the test is redone. See also
Appendix F and Appendix A.
HG is an 'Ozone Only' command and will not execute in the NO
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MKIV OPERATOR'S MANUAL
Mode.
2
mode.
2
3
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