Kipp&Zonen Brewer MkIII - Manual (Page 109)

MKIII OPERATOR'S MANUAL 106
Method:
The method by which direct-sun O
3
and SO
2
values are derived from the raw photon counts at the
five operational wavelengths is outlined in sections 2 and 3 of Preliminary Data Reduction. After
corrections for dark count, deadtime, Rayleigh scattering, and instrument temperature have been
applied, the O
3
and SO
2
(MS(11) and MS(10)), values are calculated using the following formulae:
2 1
1 ) 9 (
) 11 (
M A
B MS
MS
⋅
−
←
⎥
⎦
⎤
⎢
⎣
⎡
−
⋅
−
⋅ ← ) 11 (
2 3
2 ) 8 (
2
1
) 10 ( MS
M A
B MS
A
MS
where
MS(8) is the weighted double-ratio for SO
2
MS(9) is the weighted double-ratio for O
3
A1 is the differential O
3
absorption coefficient for the O
3
ratio
B1 is the extraterrestrial constant for the O
3
ratio
A2 is the relative SO
2
to O
3
absorption for the SO
2
ratio = (2.44)
A3 is the differential O
3
absorption coefficient for the SO
2
ratio
B2 is the extraterrestrial constant for the SO
2
ratio
M2 is the airmass, also referred to as MU.
The method to determine the four instrument-dependent values (A1, B1, A3, B2) for a particular
instrument via the Inter-Comparison Calibration procedure is outlined below.
Many simultaneous direct-sun measurements (at least 40) are made with both the instrument to be
calibrated and a reference instrument. Measurements should be taken over a wide range of
airmass values (1.0 < mu < 3.0) for at least one full day of good observing conditions. The O
3
and
SO
2
values (MS(11) and MS(10)) are determined from the measurements made with the reference
instrument. These values, together with the values of MS(8), MS(9), and M2 valid for the
instrument being calibrated are substituted into the above two equations which are rewritten as
follows:
MS(11) M2 A1 B1 MS(9)
⋅ ⋅ + ←
MS(11)] M2 MS(10) A2 [M2 A3 B2 MS(8) ⋅ + ⋅ ⋅ ⋅ + ←
Two least-squares linear regression fits are applied to these equations and the resulting two pairs
of regression coefficients (B1, A1; B2, A3) are the four instrument-dependent coefficients.
As for all previous tests, consult EC or KIPP & ZONEN prior to altering any of the constants in the
instrument Constants File.
AZ: ZERO THE AZIMUTH TRACKER
The AZ command re-orients the Azimuth Tracker to its zero-step position. This routine is activated
automatically following a system reset (RE command). The operator should use this command if
there is concern that the azimuth drive has lost track of where it is for such reasons as temporary
power loss to the Tracker or other physical disturbance.
Note that the AZ routine can only be accessed if the instrument configuration (IC) is setup to
include an Azimuth Tracker System.
APPENDIX F FACTORY TESTS