# Presentation: 910338

## Statusof OMI Dataprocessing

- Jacques Claas (KNMI)Phil Durbin (Adnet Systems, Inc.)

## Processing Summary

## Data processing  status

- Collection 3:
- THE dataset for L1B and L2 products.  Data are available on the DISC. Do NOT use older data.
- The L1b forward stream as well as the L2 NRT stream are very stable
- NRT data available within three hours after the overpass
- GDPS 1.1.1.1:
- The new GDPS version 1.1.1.1 has been running in forward stream from April 15th 2008 till Oct. 8th 2008
- Improvements:  > improved wavelength assignment  > improved radiance goniometry  > setting noise levels for individual pixels  > added float field in irradiance product
- GDPS 1.1.2:
- Running since Oct. 8th 2008
- Static flagging (XTrackQualityFlags) of CCD rows affected by row anomaly

- NRT image of tropospheric NO2 over Europe

- NRT image of tropospheric NO2 over Beijing

## Summary of  data processing  issues

- FMU anomaly:
- Permanent data loss for 2 orbits: 18027 – 18028 (Dec 5, 2007).
- No science data for 9 orbits: 18235 – 18243 (Dec 19-20, 2007).
- Operations software anomaly:
- No science data for 51 orbits: 22349 – 22399 (Sep 27-30, 2008)
- Row anomaly:
- Two row anomalies exist, affecting part of the OMI field of view.
- Work on correction algorithm in GDPS is on-going.
- L2 developers must carefully read the L1b readme file on the DISC.
- AURA re-phasing:
- Due to the AURA re-phasing orbits now have different geo-location.
- Current definition of NOSE parameters is not up to date. DO NOT USE!

## Impact of FMU anomaly on data processing (1/3)‏

-  Formatting Multiplexer Unit: electronics for writing to / reading from the Solid State Recorder.
-  A FMU anomaly started on Dec 4th 2007 corrupting the SSR partition 6 data containing S/C   housekeeping data and MLS plus HIRDLS science data.
-  The anomaly is most likely caused by a memory chip. The FMU behaviour was erratic at the   time of the anomaly.
-  The GBAD data that OSIPS needs for its L0 -> L1B processing is derived from the S/C   housekeeping data (attitude/ephemeris). Due to the anomaly no data processing was possible.
-  There has been no loss of OMI science data due to the anomaly. But on Dec 19th no   measurements could be performed for 8 orbits (18235 – 18242).
-  Since Dec 19th 2007 for unexplained reasons, no anomalies have been observed in the GBAD  data and HIRDLS data. MLS misses only 2-10 science packets a day.
-  In case the FMU anomaly shows up again,  either a FMU reset or a FMU swap from the  S/C A to the B-side will be performed. Based on a risk assessment procedures for this have been  developed.

## Impact of FMU anomaly on data processing (2/3)‏

## Impact of FMU anomaly on data processing (3/3)‏

- Summary:
- The GDPS needs attitude and ephemeris data for itsL0 -> L1b processing in order to determine the geo-location of ground pixels.
- Until the FMU anomaly, attitude and ephemeris data were based on GBAD data
- Since the FMU anomaly, attitude and ephemeris data are based on the OMI specific APID 1836/1837 data.
- Differences between “old” and “new” attitude and ephemeris data turn out to be very small. Differences in geo-location are less than 1% of the ground pixel size (see KNMI Technical Note 908).

## Row anomaly (1/4)‏

- A row anomaly was discovered in September 2007.This anomaly has persisted since then.
- On May 19th 2008, a new row anomaly was discovered.
- Both row anomalies impact specific CCD rows (is specific part of the OMI field of view).
- 2007 anomaly: 2 rows are affected for complete illuminated orbit.
- 2008 anomaly: 4 rows are affected for northern part of illuminated orbit.
- Current tentative explanation is that a small piece of MLI has moved into the field of view of the nadir port.
- GDPS:
- The current GDPS 1.1.2 applies static flagging of the affected CCD rows in the L1b HDF files
- A new GDPS version that will use a correction algorithm enabling dynamic flagging is under development.
- Data users must carefully read the L1b readme file on how to treat the affected CCD rows in their retrieval algorithms.

## Row anomaly (2/4): OMI L0 data

- wavelength

- X-track

- UV image from April 20

- UV image from September 11

## Row anomaly (3/4): impact on L2

## Row anomaly (4/4): impact on L2

## Impact of the AURA re-phasing on data processing (1/2)‏

-  On NASA instigation, between Dec 5th 2007 and May 8th 2008, a relocation of the  AURA satellite was performed.
-  Purpose:  - Improving the science output by combining AQUA and AURA science data    (overlapping fields of view for particular instruments, smaller time difference).  - distance before: 5918 km, distance after: 3674 km
-  Consequence:  - the OMI groundtrack has moved about 120 km eastwards (about 6 groundpixels).  - the OMI monthly spatial zoom-in measurements now have a different geo-location.  - the NOSE parameters have to be updated (not done yet!). _**DO NOT USE!!**__** **_
-  _Decision_:  - the timing of the monthly spatial zoom-in measurements will not be changed, hence    will keep the changed geo-location.

## Impact of AURA re-phasing on dataprocessing (2/2)‏

- De Bilt

- Washington

- Before re-phasing

- After re-phasing

- OMImonthlyspatial zoom-inmeasurements

## PGE to App Transition

- The OMI SIPS is re-designed to the ACPS (Atmospheric Composition Processing System)
- Instead of developing L2 PGE’s for the OMI SIPS, scientists must now develop App’s that run on the ACPS.
- Main differences/advantages:
- Can be run directly from TLCF or user workstations.
- Quicker delivery mechanism because it uses automatic checking of the App structure.
- Uses subversion (svn) instead of CVS as a code repository.
- A 3-6 month OSIPS/PGE -> ACPS/App transition period began in July.SIPS team does conversion and training.
- Existing and older PGE's will still be available but source code in CVS will be read only.