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Calibration & 0-1b data processing

Calibration & 0-1b data processing. 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.

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Calibration & 0-1b data processing

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  1. Calibration&0-1b data processing Marcel Dobber (KNMI)

  2. 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

  3. Calibration team • Quintus Kleipool (KNMI) • Marcel Dobber (KNMI) • Glen Jaross (SSAI / NASA) • Support by TMCF team: • Nico Rozemeijer • Remco Braak

  4. 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.

  5. Optical degradation • Optical degradation: • Smaller than 2% in UV1, smaller than 1% in UV2 and VIS. Sun, UV2 channel WLS, VIS channel

  6. GDPS status • v1.0.0: • Used for reprocessing in ECS-3. • Same version as 0.9.18. • 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.

  7. OPF status • OPF 41 → TDOPF • for GDPS v1.0.0, used for reprocessing. • started using TDOPF in forward mode with orbit 16307 (9 August 2007). • OPF 43 • OPF parameters for GDPS v1.1.0 and v1.1.1. • OPF 44 → TDOPF • Updated SAA definition parameters. • for GDPS v1.1.1 • started using TDOPF in forward mode with orbit 19950 (15 April 2008).

  8. Current processing collection 3 • Used for processing in ECS-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.

  9. 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 25-27 June 2007. • Seems to have optical origin rather than electronical. • Can be seen in level-0, level-1b and level-2 data.

  10. Row anomaly row 53 (UV2, VIS)

  11. 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 !

  12. Row anomaly May 2008 Row 40 nadir Row 53 West East Solar port

  13. Row anomaly May 2008 Row 40 nadir West Row 53 East Solar port

  14. Row anomaly May 2008

  15. Row anomaly May 2008 • Stability (in rows and in time) of the row anomaly: UV1

  16. OMI surface reflectance • Surface reflectance based on histogram method.

  17. OMI surface reflectance • OMI minimum mission LER

  18. OMI surface reflectance • Comparison with TOMS (Herman and Celarier, 1997).

  19. OMI surface reflectance • Comparison with GOME (Koelemeijer et al., 2001). • OMI also compared with MODIS black sky albedo at 470 nm.

  20. OMI surface reflectance

  21. OMI surface reflectance • Used all data from October 2004 to October 2007. • 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).

  22. 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.

  23. Web site collection 3 • http://www.knmi.nl/omi

  24. 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.

  25. UV part

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