# Presentation: 203074

## NOAA GOME-2 Cal/Val Plans

- L. Flynn, Co-Chair
-  Atmospheric Chemistry POP
- with input from S. Kondragunta, Z. Zhang, Y. Pachepsky and the GOME-2 website

## Outline

- Status
- Calibration and Format documents obtained
- Sample and Proxy Measurements obtained
- Measurements
- Calibration and Characterization Parameters
- Validation, Soft Calibration and Maintenance
- Product Development and Implementation Status
- Further product development plans and need for support

## Global Ozone Monitoring Experiment (GOME-2)

**Notes:**
The instrument is almost a carbon copy of the GOME concept: A scan mirror directs the light reflected from the Earth atmosphere into the instrument telescope. Additionally, the scan mirror can point to the Sun diffuser and to internal calibration light sources. Behind the entrance slit of the telescope the light is collimated onto a Brewster/pre-disperser prism configuration to split from the main light beam a s- and p-polarized light beam, which is directed to the Polarization Measurement Unit (PMU). Subsequently the main beam is separated with respect to the spectral coverage of the four main channels by a channel separator prism and a dichroic filter. Finally the light is dispersed by four gratings and focused by four objectives onto a silicon linear detector array in the Focal-Plane Assembly.
To achieve an accurate radiometric in-orbit calibration of the instrument, GOME-2 has two internal calibration light sources, one of which offers well-isolated spectral lines in the required wavelength range and a white light source (WLS) for the broadband continuum. The WLS, which is not part of the GOME calibration unit, is used to monitor the etalon that is present on the cooled Reticon detectors, due to freezing water vapor . Pt/Cr/Ne hollow cathode discharge lamp.

## GOME-2 Measurements

- Vis4 (590-690nm) Vis3 (401-600)                      UV2 (311-403nm) UV1b (290-315nm)
- Every 3/16 S (80 KM by 40 KM at nadir)
- 6S, 24 + 8 measurement, 1920 km cross-track
- UV1a (240-290 nm)
- 1.5 S 3 cross track measurement plus 1 fly-back.
- More frequent sample during IOV
- Vis3 has visible wavelengths for NO2 and better aerosol products
- PMD 10 KM by 40 KM (290-800nm)
- Six of the 15 channels mimic TOMS wavelengths
- 3-Minute Granules contain 30 scans, 960 spectra
- Solar Spectrum at least once per day

**Notes:**
GOME-2 contains two spectrometers - one to measure the radiance component of light that is reflected from the Earth atmosphere in the direction of the satellite (the main channels), in the spectral range 240-790 nm with a resolution of 0.24-0.53 nm and another spectrometer to characterize simultaneously the state of polarization of the same spectrum (the Polarization Measurement Unit). The instrument is almost a carbon copy of the GOME concept: A scan mirror directs the light reflected from the Earth atmosphere into the instrument telescope. Additionally, the scan mirror can point to the Sun diffuser and to internal calibration light sources. Behind the entrance slit of the telescope the light is collimated onto a Brewster/pre-disperser prism configuration to split from the main light beam a s- and p-polarized light beam, which is directed to the Polarization Measurement Unit (PMU). Subsequently the main beam is separated with respect to the spectral coverage of the four main channels by a channel separator prism and a dichroic filter. Finally the light is dispersed by four gratings and focused by four objectives onto a silicon linear detector array in the Focal-Plane Assembly. The minor changes to the design of the GOME spectrometer may be summarized as followed: 1. GOME-2 has a more complex Polarization Measurement Unit (PMU) than GOME, which measures simultaneously s- and p-polarized light on a spectral resolution between 2.8 nm at 312 nm and about 40 nm at 790 nm.
2.  To achieve an accurate radiometric in-orbit calibration of the instrument, GOME-2 has two internal calibration light sources, one of which offers well-isolated spectral lines in the required wavelength range and a white light source (WLS) for the broadband continuum. The WLS, which is not part of the GOME calibration unit, is used to monitor the etalon that is present on the cooled Reticon detectors, due to freezing water vapor .3.  The maximum swath width is increased to 1920km across track in order to address the user requirement of global coverage in one day. In conjunction with this change the scan speed is adjusted to minimise the effect of oblique viewing and provide a constant scan rate on the ground. However, the scans is completely reprogrammable in-flght allowing an almost unlimited choice of scan profiles.4. The width of the entrance slit is increased from 0.1 mm for GOME to 0.2 mm fro GOME-2, which avoids the spectral undersampling of the spectrometer.5.  The coating of the different optical elements is changed to reduce both a steady out-gassing of the coating experienced with GOME and the straylight component measured by the detectors.6.  Due to a different groove profile of the gratings the polarization sensitivity of the main channels is considerable lower than for GOME. More details on the GOME spectrometer concept can be found on our GOME-website.  The optical layout of the GOME-2 spectrometer.The integration time can be separately set for each channel; in channel 1 and 2 it is possible to sub-divide the channel in two parts (called 'band 1a', 'band 1b' and 'band 2a, 'band 2b' respectively) having separate integration times. It is anticipated that a default integration time of 0.1875ms will be used in all channels with two exceptions where longer integration times are needed because of low light intensity: (i) Band 1a has a default integration time of 1.5 seconds (yielding three spectra per scan and one from the fly-back with the possibility of co-adding spectra to improve signal to noise characteristics). (ii) The integration time for all channels will be increased for low solar elevations (high solar elevation angles). For the 1920km swath, the maximum temporal resolution of 187.5ms for the main channels (23.4ms for the PMD channels) corresponds to a maximum ground pixel resolution (across-track x along-track) of 80km x 40km (10km x 40km for the PMDs) in the forward scan.

## http://ftp.sron.nl/index.php?option=com_content&task=view&id=193&Itemid=125 

-  Band  Pixel centers nm   Pixels Pixel FWHM nm  0        Spare  1     311.8-314.3        5        3.1  2     316.9-318.8        4        3.3  3     321.5-329.3       12        3.5  4     330.8-334.6        6        3.8  5     336.2-363.1       44        4.8  6     380.3-383.9        4        6.1  7     399.8-428.0       19        7.8  8     435.1-552.4       46       12.5  9     552.4-556.2        2       18.7 10     567.9-680.0       24       25.2 11     743.1-750.8        4       38.5 12        758.8           1       40.2 13        792.4           1       43.9 14        Spare

- Proposed PMD Channels

## Input Required by the Algorithms

**Standard Ozone Wavelengths or DOAS Spectral Windows**
**Radiance (corrected for calibration, polarization, non-linearity and dark current)**
**Irradiance (corrected for calibration, polarization, goniometry, Doppler, non-linearity, and dark current)**
**Wavelength Scales for Earth and Solar**
**Geolocation information**
**Satellite viewing angles and solar zenith and azimuth angles**
**Ancillary data sets (climatology, forecast or retrieved)**

## Calibration and Validation Checks

**Wavelength Scale/Shape **
**Solar Lines, Neon/Argon Lamp**
**Noise, offsets, and transients **
**Night-side and continuity**
**IB and OOB stray light**
**Correlation with reflectivity**
**Filling in of solar lines in Earth view**
**Polarization correction**
**w/wo clouds, PMD correlation with changes**
**Reflectivity distribution**
**Total ozone pairs (A, B and D)**
**Initial and final residuals**
**Intercomparisons with Satellite and GB**

## Internal and Soft Calibration and Validation Sequence for Total Ozone

- 1. Check 331-nm reflectivity channel calibration by using global distributions of reflectivity – minimum ocean (4%) and land (1%) reflectivity, maximum global reflectivity and ice radiances (Greenland and Antarctica).
- 2. Check agreement between 360-nm reflectivity and 331-nm reflectivity for scenes with reflectivity greater than 80%.
- 3. Compute total ozone for nadir measurements from B-pair (317.5-nm and 331-nm) in the tropics and compare to expected values.
- 4. Check agreement of other ozone sensitive channels/pairs with the B-pair results.
- 5. Check agreement between zonal means at each satellite view angle and the nadir zonal means.
- 6. Compare ozone and reflectivity results for different channels and pairs as functions of solar zenith angles and reflectivity.

- _Methods developed at NASA GSFC over the last 30 years._

**Notes:**
Pair Justification
Spectral Discrimination
Ice Radiances
NASA GSFC work over the last 30 years.

Algorithms are designed to use ratios, and ratios of ratios.

## Products Under Development

- Total Ozone: V8, *PMD V8*, and DOAS
- Profile Ozone: V8, SAF, GSFC/SAO
- SO2 estimates: V8, UMBC, OMI
- Trace gases (NO2 etc.): AQ, SAF, OMI/SAO
- Aerosols: V8, SAF, PMD V8, OMI/UMBC, AQ
- Cloud height: SAF, OMI O2-O2 or Ca H&K
- SAF = Satellite Applications Facility
- AQ = Air Quality R&D in StAR
- V8 = PSDI/GSDI algorithm implementation

## Near Real Time Products from GOME-2

**Data Acquisition (MetOP)**

- Raw data

- Level 1B

**Total and profile ozone, Clear-sky UV, aerosols**

**Total Ozone**
**Profile Ozone**
**Aerosol Index**
**Nitrogen dioxide**
**Sulfur dioxide**
**Formaldehyde**
**Aerosol Optical Depth*******
**Bromine and Chlorine compounds*******

**By 2007**

**By 2008**

***funding anticipated**

## V8 TOZ progress

- Read in Earth sample radiance at selected channels
- Read in Solar irradiance at selected channels
- Adjusted wavelength scale and computed albedos
- Created Look-Up Tables with bandpasses
- Read in SZA, SAA and SVA
- Created flags and formatted output file
- Ran with test granules in pipeline processing

**Notes:**
Were asymmetric bandpasses used?

## Slide 12

## Slide 13

## Slide 14

**Notes:**
Need to use asymmetric bandpasses.

## V8 Profile Progress

- OMI Nadir Retrievals
- Similar input to Total Ozone
- more wavelengths and data from Channel 1 and Channel 2
- Off-nadir retrievals under development
- Complications from Channel 1a
- large FOV / different integration times
- Sample short integration data during IOV
- Signal to Noise Ratio is poorer
- Stray Light may need corrections
- Polarization correction is from extrapolation

## DOAS Trace Gas Products

| Retrieved species  | Fitting window  | Reference spectra  |
| --- | --- | --- |
| O3  | 325 - 335 nm  | O3, Ring |
| O3, NO2  | 425 - 450 nm  | O3, NO2, Ring  |
| HCHO  | 336.5 - 357.5 nm  | HCHO, O3, NO2, BrO, O4, Ring  |
| BrO  | 345.6 - 359.0 nm  | BrO, NO2, O3, (OClO), Ring  |
| SO2  | 313.5 - 327.0 nm  | SO2, O3, Ring  |
| OClO  | 357.0 - 381.5 nm  | OClO, NO2, O4 |

- CHO-CHO may be retrievable in the 430 – 460 nm fitting window.

## Total Ozone Products

- May need some support for contractor to perform and implement soft calibration analysis outlined on next slide if Level 1b calibration is not of high quality
- May need some support for validation
- Comparisons to SBUV/2 Total Ozone
- Comparisons to OMI and TOMS TOZ
- Comparisons to Ground-based Dobson
- Comparisons to other solar irradiance spectra
- Need support to implement high resolution TOZ from PMD

## Future Tasks for GOME-2

- TOZ
- Complete Documentation & Implementation (S)
- Provide Maintenance and Adjustments (P)
- Perform Validation of TOZ (P)
- Adapt and Implement V8 PMD product (N)
- Profile Ozone
- Complete Adaptation & Implementation (P)
- DOAS Trace Gases and Aerosols
- Complete DOAS Adaptation and Implementation (P)
- Implement improved SO2 product (P)
- Implement improved aerosol product (P)
- S Supported, P Partially Supported, N Funding Needed
- Assumes Base support for operational product processing
- and continued Air Quality development support.

## Trace Gas and Aerosol Products from MetOP GOME-2Mitch Goldberg, Shobha Kondragunta, Lawrence. E. FlynnNOAA/NESDIS Center for Satellite Applications and Research&James. J. Szykman and Richard ScheffeEnvironment Protection Agency NERL/ORD

- Trace Gas and Aerosol Products from MetOP GOME-2Mitch Goldberg, Shobha Kondragunta, Lawrence. E. FlynnNOAA/NESDIS Center for Satellite Applications and Research&James. J. Szykman and Richard ScheffeEnvironment Protection Agency NERL/ORD

## MetOP GOME-2 

- MetOP GOME-2

- GOME-2
- July 17, 2006 launch on MetOP-1into 9:30 AM orbit
- UV/VIS sensor (240 nm – 790 nm) for atmospheric chemistry and air quality
- Pixel resolution 40 X 80 km2.  Polarization measurements at select wavelengths at 40 X 10 km2. Very useful for retrieving aerosol properties
- Will provide tropospheric amounts of ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, glyoxal, aerosols with ability to distinguish between dust/smoke vs urban/industrial aerosols.  Most of these products are EPA designated criteria pollutants for air quality
- Heritage instrument: ERS-2 GOME-1
- 1995-2002
- DOAS algorithms developed to make use of hyperspectral coverage.  Algorithms easily adaptable to GOME-2
- Data widely used in air quality modeling and assessment.  Applications limited to monthly and seasonal time scales due to large footprint of GOME-1 (~250 km)

**Reichter et al. (Nature, 2005) using GOME data showed that NO****x****emissions in the U.S. are decreasing but increasing in Asia.  EPA wants to extend this record to 2030 with GOME-2 data to track newly implemented Clean Air Interstate Rule**

- US

- China

## User Needs

- EPA
- Track Clean Air Interstate Rule (CAIR).  Are NOx and SO2 controls working?  Is visibility improving in our national parks?
- Long-term monitoring from satellites critical to track trends
- NWS
- Improve air quality forecast accuracy
- Near real term monitoring from satellites critical for satellite data assimilation

**National NO****x**** and SO****2 ****Power ****Plant Emissions:****Historic and Projected with CAIR**

**474 Counties with a population of 159M in non-attainment**

**Notes:**
This and the next slide is a summary of user needs that came out of the air quality breakout session at the 2003 GOES-R users conference.

## EPA Timeline for Use of GOME-2 data for Air Quality Applications involves on-going collaboration with NOAA & NASA

**EPA Timeline for Use of GOME-2 data for Air Quality Applications involves on-going collaboration with NOAA & NASA**

**Applications Research**

**Validation & Verification**

**Applications Demonstration**

**2004 - 2008**

**2008- 20012**

**2012 and beyond**

**SCIENCE**

**Nationwide**
**Data**

**APPLICATIONS**

**Implementation as**
**Air Quality**
**Management Tool (mature products)**

**On-going involvement from EPA, State, Local, and Tribal Air Quality Management Organizations**

**On-going studies on use of **
**GOME, SCIA and OMI data.**
**Demonstrate Linkages of **
**Regional Scale Satellite**
**Measurements to In-situ**
**measurements and emission**
**inventories.**

**Evaluate GOME-2 operational products.**
**Intercomparison and continuity studies with heritage sensors.  Evaluation of first 5 year of GOME-2 data for trends.**

**On-going assessment of air quality trends with**
**GOME-2 data  against traditional benchmark data sets and incorporation into as an indicator for accountability. **

**GOME, SCIA, OMI **
**(NASA) sensors provide**
**prototype data sets for**
**GOME-2. (**Ozone, NO2,
- SO2, Aerosol, HCHO)

**NOAA/NESDIS  starts production of air quality GOME-2 data products.**

**GOES-R and potential future NASA Geostationary**
**tropospheric chemistry missions.**

**Operations**

## Shortfalls that Must be Met

- To meet user requirements, NESDIS has to invest substantial effort towards algorithm and product development
- Acquire capabilities,
- Use Aura OMI and Envisat SCIAMACHI data as risk reduction,
- Collaborate with the group at Harvard Smithsonian Astrophysical Organization (SAO) which developed OMI trace gas algorithms,
- Collaborate with NASA scientists who developed OMI total ozone and aerosol product algorithms (this falls under NASA Research to Operations activity),
- Coordinate with the users on product development and user application