calibration & 0-1b data processing

OMI calibration STM 13Calibration
0-1b data processing
Marcel Dobber (KNMI)
OMI ST Meeting 13, 24-27 June 2008 Slide * Marcel Dobber, KNMI
Contents
Conclusions
Calibration team
Nico Rozemeijer
Remco Braak
Status CCD detectors: Pixels with permanently increased dark current as function of time
03 June 2008 (1418 days after launch)
UV: 43% of all unbinned pixels (image area)
VIS: 45% of all unbinned pixels (image area)
As expected, still increasing linearly.
Chart1
36
36
58
58
75
75
101
101
125
125
133
133
139
139
158
158
205
205
316
316
501
501
571
571
1014
1014
1418
1418
UV (blue) and VIS (red) (unbinned) CCD detector hot pixels
0.0077993311
0.007451505
0.0124370123
0.0123455964
0.0152151616
0.0152173913
0.0237369008
0.0240958751
0.0309186176
0.0312753623
0.0363166109
0.0367848384
0.0385507246
0.0386510591
0.0408428094
0.0406867336
0.0568940914
0.0577458194
0.0909966555
0.0909386845
0.1476544036
0.1496120401
0.1695362319
0.1756209588
0.309017
0.320473
0.434004
0.453534
Blad1
Date
Number of pixels with permanently increased DC
UV (blue) and VIS (red) detector pixels with permanently increased dark current
Blad2
UV
UV detector pixels with permanently increased dark current
Blad3
Fraction of (unbinned) pixels with permanently increased DC
UV (blue) and VIS (red) detector pixels with permanently increased dark current
Days since launch
Days since launch
UV (blue) and VIS (red) (unbinned) CCD detector hot pixels
Optical degradation
Optical degradation:
Smaller than 2% in UV1, smaller than 1% in UV2 and VIS.
WLS, VIS channel
Sun, UV2 channel
GDPS status
Same version as 0.9.18.
changes in wavelength assignment algorithm:
avoid large wavelength shifts from erronous small pixel column (SPC) signals.
interchangeably use SPC UV2-VIS when necessary.
clip irradiance goniometry correction algorithm.
additional float field in level-1b irradiance.
possibility for pixel-dependent noise.
bug fix in attitude and ephemeris L0PP.
OPF status
for GDPS v1.0.0, used for reprocessing.
started using TDOPF in forward mode with orbit 16307 (9 August 2007).
OPF 43
OPF 44 → TDOPF
for GDPS v1.1.1
started using TDOPF in forward mode with orbit 19950 (15 April 2008).
Current processing collection 3
GDPS 1.1.1 as of 15 April 2008.
TDOPF software + system, version 13.02.
Integrated TMCF PGEs.
OPFs are updated automatically daily with automatic quality checks.
Row anomaly row 53 (UV2, VIS)
In row 53 in UV2 and VIS in level-1b data (0-based).
Suppresses signals by 20-30% in UV2 and VIS over complete illuminated orbit.
At the north pole the signal decrease changes into signal increase (sun light reflection).
Not visible in UV1.
First appeared around 25-27 June 2007.
Seems to have optical origin rather than electronical.
Can be seen in level-0, level-1b and level-2 data.
Row anomaly row 53 (UV2, VIS)
Row anomaly May 2008
Rows 18-21 in UV1, 38-41 in UV2 and VIS in level-1b data (0-based).
First appears on 11 May 2008 and further increases on 16 May 2008.
In UV2 and VIS similar as row 53 anomaly, but:
new anomaly appears only after nTimes=1140 on northern hemisphere (14 minutes prior to sun_elev_angle=0 degrees).
New anomaly shows strong sun light reflection in UV1, UV2, VIS, only after nTimes=1140, almost 10x more signal than radiance in UV1.
Look in Level-1b readme file !
Solar port
Solar port
Stability (in rows and in time) of the row anomaly:
UV1
OMI surface reflectance
Surface reflectance based on histogram method.
OMI minimum mission LER
Comparison with TOMS (Herman and Celarier, 1997).
Comparison with GOME (Koelemeijer et al., 2001).
OMI also compared with MODIS black sky albedo at 470 nm.
0.5 degree x 0.5 degree.
Mission minimum surface albedo product.
Monthly minimum surface albedo products (seasonal dependence).
23 wavelengths in range 328-500 nm (spectral dependence).
6 wavelengths in UV2/VIS overlap region, 1 wavelength in UV1/UV2 overlap region.
OMI surface reflectance map tested with NO2, aerosol and cloud (O2-O2).
Future work
Investigation row anomalies and possibilities for correction in level-1b data.
Impact of rephasing (NOSE block parameters, sun angles).
Continue to monitor potential optical degradation behaviour using WLS and solar spectra.
Current optical degradation < 1.5% in 270-500 nm wavelength range.
This does not take into account degradation of the primary telescope mirror.
Continue to monitor CCD detector degradation behaviour.
Continue work on surface albedo (swath angle dependence).
Continue validation Earth reflectances (including swath angle dependence), BSDF structures, Earth reflectance interchannel jumps, degradation primary telescope mirror.
Web site collection 3
http://www.knmi.nl/omi
Conclusions
Detector degradation under control.
TMCF runs as expected.
OM surface reflectance database.
UV part
5 cm
1.00E+08
1.00E+09
1.00E+10
1.00E+11
1.00E+12
Cross Track Position / Row
0.00E+00
5.00E+12
1.00E+13
1.50E+13
2.00E+13
2.50E+13
Cross Track Position / Row
pixels
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
02004006008001000120014001600
pixels

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