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Data Products

Overview

Level 1B product
Level 2 NRT product
Level 2 NRT meteo product
Level 2 off-line

Simulated radiance for the solar occultation geometry
Simulated radiance for limb geometry
Simulated radiance for the nadir geometry

 

Overview

The table below presents the list of SCIAMACHY data products. According to the potential use of the data and the complexity of algorithms, the product generation has been split between near real time (NRT) processing (products available three hours after data acquisition) and off-line processing.

Nadir Limb
UV/Vis IR UV/Vis/IR UV/Vis IR UV/Vis/IR
NRT O3*, NO2, SO2*, OClO*, H2CO* H2O, CO, N2O, CH4 Clouds, Aerosols      
Off-Line O3, NO2, BRO,
SO2*, OClO*,
H2CO* 		H2O, CO, CO2, N2O, CH4, P, T Clouds, Aerosols O3, NO2, BrO H2O, CO, CO2, N2O, CH4, P, T Aerosols

(*) These molecules can only be detected under special conditions
(*) O3 profiles from nadir measurements as well as stratospheric profiles from occultation measurements may be implemented at a later stage
(*) Aerosol stratospheric profiles may be implemented at a later stage.

Note: Links in table are internal links in this page.

SCIAMACHY

Processing Level

Product ID

Size Mbytes / Coverage

Level 1b Geolocated engineering calibrated
Scientific measurements only
(Nadir, limb, sun/moon occultations)

Monitoring measurements : 
- Sun over diffuser
- Subsolar calibration
- Spectral lamp measurements
- White light source measurements
- Elevation mirror (moon/sun) monitoring
- ADC calibration

SCI_NL_1P

180Mb / Full Orbit

Level 2
  • Geolocated vertical columns for O3, NO2, H2O, CO,N2O, and CH4
  • Geolocated vertical columns for SO2, OClO, and H2CO under special conditions (volcanic eruption, ozone hole conditions, pollution)
  • Cloud top height and cloud cover
  • Aerosol absorption indicator
SCI_NL__2P

5 Mb/dayside

Level 2

Nadir
Geolocated vertical column amounts of 03, NO2, OC10, SO2, H2CO, BrO, cloud fractional cover and top height, Aerosol absorption indicator
Limb
Stratospheric profiles of 03, N02, Br0, H20, CO, CH4, Pressure, Temperature

SCI_OL_2P

Level 2 Vertical column amounts of ozone for meteo users (BUFR Format) SCI_RV__2P

1Mbyte/dayside

Level 1B product

Level 1B products are geolocated engineering calibrated data. In the case of SCIAMACHY , they store individual spectra corresponding to the different scientific modes (nadir, limb, sun/moon occultations) spectrally and radiometrically calibrated as well as a solar reference spectrum.

In order to support SCIAMACHY calibration/monitoring activities, the level 1b also includes individual measurements corresponding to special monitoring states : Sun over diffuser calibration, Subsolar Calibration, SLS and WLS spectra, Elevation mirror monitoring and ADC calibration.

In order to limit the size of the level 1b products and to extend the potential range of applications for those products, it was decided to keep the raw measurements within the product. Some dedicated GADSs contains all preprocessed calibration data (e.g. spectral calibrations curves, straylight figures figures ...) to perform the necessary corrections. Therefore , together with the level 1b products themselves, users will receive and extraction software which will allow them to obtain the final calibrated products by applying a selected set of corrections. In this sense the same products can be used for level 2 processing

The following diagram shows the internal organization of the level 1b products. It assumes some knowledge about the general structure of all Envisat products.


The internal organization of the level 1b products
Diagram Courtesy of DLR/DFD

The main tasks of the Level 1b processing cover the following aspects:

  • Geolocation/geometry, depending on the instrument mode
    • Ground pixel latitude/longitude
    • Tangent point latitude/longitude, tangent height
    • Sun zenith/azimuth angle
  • Calibration
    • Spectral calibration using the onboard spectral lamp or solar Fraunhofer lines
    • Leakage current correction/thermal background removal
    • Pixel to pixel gain,
    • Etalon shift correction (varying interference pattern)
    • Straylight correction
    • Diffuser BSDF correction for solar measurements
    • Polarization correction
    • Radiometric calibration
PRODUCT ID SCI_NL__1P
NAME Localized atmospheric spectra in the UV/Vis/near IR wavelength range
DESCRIPTION Geolocated, radiometrically and spectrally calibrated limb and nadir radiance spectra. Limb measurements cover both, scattered and solar/lunar occultation spectra (see below for more information on these spectra).

Individual measurements from dedicated monitoring states:
- Sun over diffuser
- Subsolar calibration
- Spectral lamp measurements
- White light source measurements
- Elevation mirror monitoring (Sun/Moon)
- ADC calibration
COVERAGE Nadir measurements:

Instantaneous field of view (IFOV): approx. 0.045° x 1.8°

0.045° width aligned in scan direction (orthogonal to flight direction)

1.8° width aligned in flight direction

Max. swathwidth: 960 km wide (in scan direction)
Typical footprint 30 km (along track) x 60 km (across track)

Limb measurements:

Instantaneous field of view (IFOV):

approx. 0.045° (elevation) x 1.8° (azimuth)

approx. 0.045° x 0.72° (sun measurements)

Tangent height range: 0 km ... 100 km

Scanning: azimuth scans are performed for constant elevation angle, typically 34 elevation steps per limb scan. Maximum azimuth range: +/- 44° relative to S/C velocity.
Note: The azimuth range is adjusted to observe the same atmospheric volume as for nadir measurements within five minutes.

THROUGHPUT 270 kbps
GEOMETRIC RESOLUTION Nadir measurements:

Spatial resolution: 30x27 to 30x240 km
Typical spatial resolution: 30 km (along track) x 60 km (across track)

Limb measurements:

Vertical resolution: approx. 3 km

Horizontal resolution: typically 120 km ... 960 km (depends on azimuth scan range, scan speed, tangent height and optical properties of the atmosphere)
SIZE 200 Mbytes per orbit
RADIOMETRIC RESOLUTION Radiometric resolution: 16 bits

Spectral resolution: 0.24 nm ... 1.5 nm (depends on spectral range)

RADIOMETRIC ACCURACY Sun normalized radiometric accuracy:

2% ... 3 % (unpolarized light)

3 % ... 4 % (polarized light)

Relative radiometric accuracy: < 1 %

Spectral accuracy: 0.005 nm ... 0.035 nm

AUXILIARY DATA orbit, attitude data, atmospheric refraction index profiles

 

Level 2 NRT products

Level 2 NRT products are based on nadir measurements only. Limb and sun/moon occultations will be processed by off-line processors. The main content of this product as detailed in the table below will be:

  • Vertical column amounts of O3, NO2, H2O,N2O, CO, CH4,OClO, H2CO, SO2
    • In the UV/Vis regions, the retrieval will be based on DOAS (Differential Optical Absorption Spectroscopy)
    • In the near-infrared, a new algorithm called BIAS is currently under development.
  • Cloud fractional cover and top height
    • The algorithm will be based on ICFA (nitial Cloud Flagging Algorithm) which is currently used on GOME and is based on the absorption depth of the Oxygen A-band around 765 nm.
    • In order to retrieve cloud cover and top height, the improved algorithm will also make use of the PMDs that can be considered as an imaging device, and which, by proper thresholding techniques, provide cloud cover information.
  • Aerosol absorption indicator
    • The algorithm (SARA) will be based on techniques already used for TOMS.

The diagram below shows in a simplified way the different modules of the level 2 NRT processor


The different modules of the level 2 NRT processor in asimplified way

The following diagram gives the internal structure of level 2 NRT products


The internal structure of level 2 NRT products

 

PRODUCT ID SCI_NL__2P
NAME Vertical column amounts of various trace gases.
DESCRIPTION Atmospheric trace gas column densities for O3, ,NO2, H2O,N2O, CO, CH4,OClO, H2CO, SO2

Cloud coverage and top height.

Aerosol Absorption Indicator.
COVERAGE Nadir measurements:

Instantaneous field of view (IFOV): approx. 0.045° x 1.8°

0.045° width aligned in scan direction (orthogonal to flight direction)

1.8° width aligned in flight direction

Maximum swathwidth: 960 km wide (across track)
Typical footprint: 30 km (along track) x 60 km (across track)
THROUGHPUT 15 Kbits per second
GEOMETRIC RESOLUTION Nadir measurements:

Spatial resolution: Variable (depends on scan speed and integration time)
30*27 - 30*240 km
Typical : 30 km (along track) x 60 km (across track)
SIZE 11.5 Mbytes per orbit
RADIOMETRIC ACCURACY
AUXILIARY DATA Spectroscopic data, climatology data, vertical p, T profiles, total column densities and profile data of O3, H2O, Air Mass Factor tables.

Level 2 NRT meteo product

This product is derived from the main SCI_NL__2P product (see above). It contains ozone vertical column amounts together with the necessary time and geolocation information. Those products are written in BUFR format widely used by the meteorological community

PRODUCT ID SCI_RV__2P
NAME Ozone vertical column amounts for meteo users
DESCRIPTION Vertical column amounts of ozone for meteo users : BUFR format.
Includes timing and geolocation information.
COVERAGE Nadir measurements:

Instantaneous field of view (IFOV): approx. 0.045° x 1.8°

    0.045° width aligned in scan direction
    (orthogonal to flight direction)

    1.8° width aligned in flight direction

Maximum swathwidth: 960 km wide (across track)
Typical footprint: 30 km (along track) x 60 km (across track)

With the maximum swath, a global coverage of the earth is achieved within 3 days.
THROUGHPUT ~ 1 Kbits per second
GEOMETRIC RESOLUTION Nadir measurements:

Spatial resolution: variable
(depends on scan speed and integration time)
30*27 - 30*240 km
Typical : 30 km (along track) x 60 km (across track)
SIZE 1 Mbyte per orbit
RADIOMETRIC ACCURACY
DATASET
AUXILIARY DATA Spectroscopic data, climatology data, vertical p, T profiles, total column densities and profile data of O3, H2O, Air mass factor tables
NOTES

Level 2 Off-Line Products

NADIR

  • Vertical column amounts of 03, NO2,OClO, SO2 , H2CO, BrO
  • In the UV/VIS regions, the retrieval will be based on DOAS (Differential Optical Absorption Spectroscopy)
  • In the near-infrared an algorithm called BIAS (Basic Infra-red Absorption Spectroscopy) will be used.
  • Cloud fractional cover and top height
  • The algorithm will be based on ICFA (initial Cloud Flagging Algorithm) which is currently used in GOME. It is based on the absorption depth of the Oxygen A-band around 765 nm.
  • Aerosol absorption indicator.
  • The aerosol absorbing indicator algorithm (AAIA) will be used.
  • Algorithms are identical to their NRT counterpart.

LIMB

  • Stratospheric profiles of 03, NO2 ,BrO, H2O,N2O,CO,CH4, Pressure, Temperature
  • Stratospheric profiles of Aerosol
  • Retrieval will be based on onion peeling Model (also called global fitting).

The diagram below shows in a simplified way the different modules of the level 2 off-line processor.

The following diagram gives the internal structure of the level 2 off-line product.

 

PRODUCT ID

SCI_OL__2P

NAME

Vertical columns and stratospheric profiles of various trace gases.

DESCRIPTION

Nadir
Vertical column amounts of O3, NO2, OC1O, H2CO, Br0
Cloud fractional cover and top height
Aerosol absorption indicator

Limb
Stratospheric profiles of O3, NO2, BrO, H2O, N2O,CO, CH4

COVERAGE

Nadir measurements

Instantaneous field of view (IFOV): approx. 0.0045 X 1.8

0.0045 width aligned in scan direction (orthogonal to flight direction)

1.8 width aligned in flight direction

Maximum swath-width: 960 km wide (across track)

Typical footprint: 30 km (along track) x 60 km across track)

Limb measurements

IFOV: approx. 0.045 (elevation) x 1.8 (azimuth)

Tangent height range (0 km … 100 km)

THROUGHPUT

20 … 24 Kbits per second

GEOMETRIC RESOLUTION

Nadir measurements

Spatial resolution depends on scan speed and integration time, the latter driven by optical properties of the atmosphere (latitude dependend).

Typical values 30 X 30 to 30 X 240 km

Limb measurements

Vertical resolution: 3 km

Horizontal resolution: 240 to 960 km (depending on scan range, scan speed, tangent height and optical properties of the atmosphere)

SIZE

15 … 18 Mbytes per orbit

RADIOMETRIC RESOLUTION

Spectral resolution: 0.24 … 1.5 nm (depends on spectral range)

Radiometric resolution: 16 bits

RADIOMETRIC ACCURACY

Sun normalised radiometric accuracy:

2% … 3 % (un-polarised)

3% … 4 % (polarised)

Relative radiometric accuracy: < 1%

Spectral accuracy: 0.005 nm … 0.035 nm

AUXILIARY DATA

Initialisation File, ECWMF Data

Simulated radiance for the solar occultation geometry


SCIAMACHY measurements for solar occultation geometry

The graph below shows simulated spectra for solar occultation geometry covering the entire SCIAMACHY wavelength range. The simulations based on MODTRAN have been run at University of Bremen for several tangent height ranging from 0 to 90 km. At 90 km (green spectrum) the simulated spectrum is almost free of atmospheric features.


Simulated spectra for solar occultation geometry covering the entire SCIAMACHY wavelength range
Image Courtesy IFE/Bremen

Simulated radiance for limb geometry


SCIAMACHY measurements for limb geometry

The graph below shows simulated spectra for limb geometry covering the entire SCIAMACHY wavelength range. The simulations based on MODTRAN have been run at University of Bremen for different tangent height ranging from 0 to 90 km.


Simulated spectra for limb geometry covering the entire SCIAMACHY wavelength range
Image Courtesy IFE/Bremen

 

Simulated radiance for the nadir geometry


SCIAMACHY measurements for nadir geometry

The graph below shows simulated spectra for nadir geometry covering the entire SCIAMACHY wavelength range. The simulations based on MODTRAN have been run at University of Bremen for three different surface albedos corresponding to three typical types of ground scene: ice (or clouds), land, or ocean.


Simulated spectra for nadir geometry covering the entire SCIAMACHY wavelength range
Image Courtesy IFE/Bremen

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry

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