OMI ST meeting June 2008 Calibration & 0-1b data processing Marcel Dobber (KNMI)

OMI ST Meeting 13, June 2008Slide 2 Marcel Dobber, KNMI Contents Status CCD detectors Optical degradation GDPS status OPF status Processing collection 3 Row anomaly row 53 Row anomaly May 2008 OMI surface reflectance Future plans OMI web site collection 3 data Conclusions

OMI ST Meeting 13, June 2008Slide 3 Marcel Dobber, KNMI Calibration team Quintus Kleipool (KNMI) Marcel Dobber (KNMI) Glen Jaross (SSAI / NASA) Support by TMCF team:  Nico Rozemeijer  Remco Braak

OMI ST Meeting 13, June 2008Slide 4 Marcel Dobber, KNMI 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.

OMI ST Meeting 13, June 2008Slide 5 Marcel Dobber, KNMI Optical degradation Optical degradation:  Smaller than 2% in UV1, smaller than 1% in UV2 and VIS. WLS, VIS channel Sun, UV2 channel

OMI ST Meeting 13, June 2008Slide 6 Marcel Dobber, KNMI GDPS status v1.0.0:  Used for reprocessing in ECS-3.  Same version as v1.1.0:  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. v1.1.1:  bug fix in attitude and ephemeris L0PP.

OMI ST Meeting 13, June 2008Slide 7 Marcel Dobber, KNMI OPF status OPF 41 → TDOPF  for GDPS v1.0.0, used for reprocessing.  started using TDOPF in forward mode with orbit (9 August 2007). OPF 43  OPF parameters for GDPS v1.1.0 and v OPF 44 → TDOPF  Updated SAA definition parameters.  for GDPS v1.1.1  started using TDOPF in forward mode with orbit (15 April 2008).

OMI ST Meeting 13, June 2008Slide 8 Marcel Dobber, KNMI Current processing collection 3 Used for processing in ECS-3:  GDPS as of 15 April  TDOPF software + system, version  Integrated TMCF PGEs. OPFs are updated automatically daily with automatic quality checks.

OMI ST Meeting 13, June 2008Slide 9 Marcel Dobber, KNMI 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. Not visible in sun or WLS measurements. First appeared around June Seems to have optical origin rather than electronical. Can be seen in level-0, level-1b and level-2 data.

OMI ST Meeting 13, June 2008Slide 10 Marcel Dobber, KNMI Row anomaly row 53 (UV2, VIS)

OMI ST Meeting 13, June 2008Slide 11 Marcel Dobber, KNMI Row anomaly May 2008 Rows in UV1, in UV2 and VIS in level-1b data (0- based). First appears on 11 May 2008 and further increases on 16 May 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 !

OMI ST Meeting 13, June 2008Slide 12 Marcel Dobber, KNMI Row anomaly May 2008 Row 53 Row 40nadir East West Solar port

OMI ST Meeting 13, June 2008Slide 13 Marcel Dobber, KNMI Row anomaly May 2008 Row 53 Row 40nadir East West Solar port

OMI ST Meeting 13, June 2008Slide 14 Marcel Dobber, KNMI Row anomaly May 2008

OMI ST Meeting 13, June 2008Slide 15 Marcel Dobber, KNMI Row anomaly May 2008 Stability (in rows and in time) of the row anomaly: UV1

OMI ST Meeting 13, June 2008Slide 16 Marcel Dobber, KNMI OMI surface reflectance Surface reflectance based on histogram method.

OMI ST Meeting 13, June 2008Slide 17 Marcel Dobber, KNMI OMI surface reflectance OMI minimum mission LER

OMI ST Meeting 13, June 2008Slide 18 Marcel Dobber, KNMI OMI surface reflectance Comparison with TOMS (Herman and Celarier, 1997).

OMI ST Meeting 13, June 2008Slide 19 Marcel Dobber, KNMI OMI surface reflectance Comparison with GOME (Koelemeijer et al., 2001). OMI also compared with MODIS black sky albedo at 470 nm.

OMI ST Meeting 13, June 2008Slide 20 Marcel Dobber, KNMI OMI surface reflectance

OMI ST Meeting 13, June 2008Slide 21 Marcel Dobber, KNMI OMI surface reflectance Used all data from October 2004 to October degree x 0.5 degree. Mission minimum surface albedo product. Monthly minimum surface albedo products (seasonal dependence). 23 wavelengths in range nm (spectral dependence). 6 wavelengths in UV2/VIS overlap region, 1 wavelength in UV1/UV2 overlap region. OMI surface reflectance map tested with NO 2, aerosol and cloud (O 2 - O 2 ).

OMI ST Meeting 13, June 2008Slide 22 Marcel Dobber, KNMI 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 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.

OMI ST Meeting 13, June 2008Slide 23 Marcel Dobber, KNMI Web site collection 3

OMI ST Meeting 13, June 2008Slide 24 Marcel Dobber, KNMI Conclusions OMI performance and calibration are in good shape:  Detector degradation under control.  Optical degradation low.  But: row anomalies. Processing collection 3 with TDOPFs. TMCF runs as expected. OM surface reflectance database.

OMI ST Meeting 13, June 2008Slide 25 Marcel Dobber, KNMI

OMI ST Meeting 13, June 2008Slide 26 Marcel Dobber, KNMI UV part