Calibration 0 1 b data processing Marcel Dobber

Calibration & 0 -1 b data processing Marcel Dobber (KNMI) OMI ST meeting 13 24 -27 June 2008

Contents l l l 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, 24 -27 June 2008 Marcel Dobber, KNMI Slide 2

Calibration team l l Quintus Kleipool (KNMI) Marcel Dobber (KNMI) Glen Jaross (SSAI / NASA) Support by TMCF team: ¾ Nico Rozemeijer ¾ Remco Braak OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 3

Status CCD detectors: Pixels with permanently increased dark current as function of time l 03 June 2008 (1418 days after launch) ¾ UV: 43% of all unbinned pixels (image area) ¾ VIS: 45% of all unbinned pixels (image area) l As expected, still increasing linearly. OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 4

Optical degradation l Optical degradation: ¾ Smaller than 2% in UV 1, smaller than 1% in UV 2 and VIS. Sun, UV 2 channel WLS, VIS channel OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 5

GDPS status l l l v 1. 0. 0: ¾ Used for reprocessing in ECS-3. ¾ Same version as 0. 9. 18. v 1. 1. 0: ¾ changes in wavelength assignment algorithm: l avoid large wavelength shifts from erronous small pixel column (SPC) signals. l interchangeably use SPC UV 2 -VIS when necessary. ¾ clip irradiance goniometry correction algorithm. ¾ additional float field in level-1 b irradiance. ¾ possibility for pixel-dependent noise. v 1. 1. 1: ¾ bug fix in attitude and ephemeris L 0 PP. OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 6

OPF status l l l OPF 41 → TDOPF ¾ for GDPS v 1. 0. 0, used for reprocessing. ¾ started using TDOPF in forward mode with orbit 16307 (9 August 2007). OPF 43 ¾ OPF parameters for GDPS v 1. 1. 0 and v 1. 1. 1. OPF 44 → TDOPF ¾ Updated SAA definition parameters. ¾ for GDPS v 1. 1. 1 ¾ started using TDOPF in forward mode with orbit 19950 (15 April 2008). OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 7

Current processing collection 3 l l Used for processing in ECS-3: ¾ GDPS 1. 1. 1 as of 15 April 2008. ¾ TDOPF software + system, version 13. 02. ¾ Integrated TMCF PGEs. OPFs are updated automatically daily with automatic quality checks. OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 8

Row anomaly row 53 (UV 2, VIS) l l l l In row 53 in UV 2 and VIS in level-1 b data (0 -based). Suppresses signals by 20 -30% in UV 2 and VIS over complete illuminated orbit. At the north pole the signal decrease changes into signal increase (sun light reflection). Not visible in UV 1. 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-1 b and level-2 data. OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 9

Row anomaly row 53 (UV 2, VIS) OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 10

Row anomaly May 2008 l l l Rows 18 -21 in UV 1, 38 -41 in UV 2 and VIS in level-1 b data (0 -based). First appears on 11 May 2008 and further increases on 16 May 2008. In UV 2 and VIS similar as row 53 anomaly, but: ¾ new anomaly appears only after n. Times=1140 on northern hemisphere (14 minutes prior to sun_elev_angle=0 degrees). New anomaly shows strong sun light reflection in UV 1, UV 2, VIS, only after n. Times=1140, almost 10 x more signal than radiance in UV 1. Look in Level-1 b readme file ! OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 11

Row anomaly May 2008 Row 53 Row 40 nadir West East Solar port OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 12

Row anomaly May 2008 Row 40 nadir West Row 53 East OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Solar port Slide 13

Row anomaly May 2008 OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 14

Row anomaly May 2008 l Stability (in rows and in time) of the row anomaly: UV 1 OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 15

OMI surface reflectance l Surface reflectance based on histogram method. OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 16

OMI surface reflectance l OMI minimum mission LER OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 17

OMI surface reflectance l Comparison with TOMS (Herman and Celarier, 1997). OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 18

OMI surface reflectance l l Comparison with GOME (Koelemeijer et al. , 2001). OMI also compared with MODIS black sky albedo at 470 nm. OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 19

OMI surface reflectance OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 20

OMI surface reflectance l l l l 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 UV 2/VIS overlap region, 1 wavelength in UV 1/UV 2 overlap region. OMI surface reflectance map tested with NO 2, aerosol and cloud (O 2 O 2). OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 21

Future work l Investigation row anomalies and possibilities for correction in level-1 b data. l Impact of rephasing (NOSE block parameters, sun angles). l Continue to monitor potential optical degradation behaviour using WLS and solar spectra. ¾ Current optical degradation < 1. 5% in 270 -500 nm wavelength range. l This does not take into account degradation of the primary telescope mirror. l Continue to monitor CCD detector degradation behaviour. l Continue work on surface albedo (swath angle dependence). l Continue validation Earth reflectances (including swath angle dependence), BSDF structures, Earth reflectance interchannel jumps, degradation primary telescope mirror. OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 22

Web site collection 3 l http: //www. knmi. nl/omi OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 23

Conclusions l OMI performance and calibration are in good shape: ¾ Detector degradation under control. ¾ Optical degradation low. ¾ But: row anomalies. l Processing collection 3 with TDOPFs. l TMCF runs as expected. l OM surface reflectance database. OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 24

OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 25

UV part OMI ST Meeting 13, 24 -27 June 2008 Marcel Dobber, KNMI Slide 26