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  2. > About GOSAT
  3. > [5] GOSAT Data Products
  1. What is GOSAT, "IBUKI"?
  2. [1] Goals of the GOSAT Project
  3. [2] GOSAT Instruments and Observational Methods
  4. [3] Methods of Analyzing GOSAT Data
  5. [4] Data Processing and Data Product Distribution
  6. [5] GOSAT Data Products
  7. [6] Validation of GOSAT Data Products
  8. [7] Project Information and Research Announcements
  9. [8] Organization and Plans

[5] GOSAT Data Products

Data products distributed from GOSAT DHF

Table 3 lists all types of the GOSAT data products provided for general users. Data users can search and order the Level 1 data (FTS Level 1B, CAI Level 1B, and CAI Level 1B+ data) and the higher level data products (FTS Level 2, CAI Level 2, FTS Level 3, CAI Level 3, Level 4A, and Level 4B data products) by accessing GOSAT DHF through GUIG (Figure 10). Among these, only the Level 1 data and some of the Level 2 data products whose uncertainties have been evaluated in our instrument calibration and data validation activities are now open to the general users. Other data products are under preparation. Tools for reading the data products are available at the GOSAT webpage (http://www.gosat.nies.go.jp/).

Table 3. List of GOSAT data products distributed from GOSAT DHF to general users. The data products underlined are currently available (as of March 2010).
List of GOSAT data products distributed from GOSAT DHF to general users. The data products underlined are currently available (as of March 2010).
Level 1B and 1B+ data

The FTS Level 1B data (Figure 8) are radiance spectra that are obtained by performing the Fourier transformation on the signals detected by FTS. The degrees to which the targeted gas species absorb the reflected and emitted light in each of the spectral bands can be seen. A single data file of the FTS Level 1B data contains the radiance spectra obtained during 1/60 of an orbital revolution (defined as "one scene").

The CAI Level 1B data (Figure 11) are pixel-by-pixel radiances obtained by multiplying the digital image data of CAI by conversion factors.

The CAI Level 1B+ data (Figure 12) carry the same Level 1B radiance data, but the geographical locations of the image pixels are corrected for the skewness caused by the topographical roughness of the ground surface and are projected onto a map of the earth via interpolation. A single data file of the CAI Level 1B and Level 1B+ data contains the radiance data obtained during 1/60 of an orbital revolution (defined as "one frame").

Figure 11. CAI Level 1B data collected on October 29, 2009 over the vicinity of mainland Japan (initial calibration performed). The image was produced by assigning colors (blue, red, and green) for the signals in the bands 1, 2, and 3.
Figure 11. CAI Level 1B data collected on October 29, 2009 over the vicinity of mainland Japan (initial calibration performed). The image was produced by assigning colors (blue, red, and green) for the signals in the bands 1, 2, and 3.
Figure 12. CAI Level 1B+ data collected on October 29, 2009 over the vicinity of mainland Japan (initial calibration performed). This image was produced by assigning colors (blue, red, and green) for the signals in the bands 1, 2, and 3.
Figure 12. CAI Level 1B+ data collected on October 29, 2009 over the vicinity of mainland Japan (initial calibration performed). This image was produced by assigning colors (blue, red, and green) for the signals in the bands 1, 2, and 3.
Level 2 data products
Figure 13. Sample of FTS SWIR Level 2 CO2 column abundance (column-averaged mixing ratios of CO2) for November 2009 derived for cloud-free scenes (initial data validation performed). Blanks in white denote no available data.
Figure 13. Sample of FTS SWIR Level 2 CO2 column abundance (column-averaged mixing ratios of CO2) for November 2009 derived for cloud-free scenes (initial data validation performed). Blanks in white denote no available data.
Figure 14. Sample of FTS SWIR Level 2 CH4 column abundance (column-averaged mixing ratios of CH4) for November 2009 derived for cloud-free scenes (initial data validation performed). Blanks in white denote no available data.
Figure 14. Sample of FTS SWIR Level 2 CH4 column abundance (column-averaged mixing ratios of CH4) for November 2009 derived for cloud-free scenes (initial data validation performed). Blanks in white denote no available data.
Figure 15. CAI Level 2 cloud flag for October 29, 2009 (initial calibration performed), overlaid with CAI Level 1B data (see Figure 14). The areas in black are under overcast sky conditions.
Figure 15. CAI Level 2 cloud flag for October 29, 2009 (initial calibration performed), overlaid with CAI Level 1B data (see Figure 14). The areas in black are under overcast sky conditions.

The FTS SWIR Level 2 data products store column abundances of CO2 and CH4 (Figures 13 and 14) retrieved from the radiance spectra in the bands 1 through 3 of FTS. Validation of the Level 2 column abundances is being carried out (explained in Chapter 6) and the results are reflected in revising the data processing algorithms. When ordering the Level 2 data products at GUIG, users can specify the observation areas and periods of their interests. The ordered data are provided to the users in a single data file.

The FTS TIR Level 2 data products are vertical concentration profiles of CO2 and CH4 derived from the radiance spectra in the band 4 of FTS.

The Level 2 cloud flag data product (Figure 15) stores the clear-sky confidence levels that are calculated from the CAI Level 1B data.

Level 3 data products

The FTS SWIR Level 3 data products (Figures 16 and 17) are generated by interpolating, extrapolating, and smoothing the FTS SWIR Level 2 column-averaged mixing ratios of CO2 and CH4 on a monthly basis. A geostatistical calculation technique called Kriging method is applied. The values are gridded to 2.5-degree cells. The FTS TIR Level 3 data products are global maps of CO2 and CH4 at several pressure levels that are processed in the same manner as above. These data products can be utilized for visualizing local highs and lows of the greenhouse gases on a global scale.

The CAI Level 3 radiance distribution data product (Figure 18) is prepared in a three-day cycle; the CAI radiance data collected during the three-day period are assembled to give a global cloud distribution map.

The CAI Level 3 global reflectance distribution (clear-sky) data product (Figure 19) shows the features of the ground surface globally. These data are prepared by selecting the least cloudy images from one month worth of the CAI Level 1B+ data and consolidating them on a global map.

The Level 3 normalized-difference vegetation index (NDVI) data are processed from the CAI radiance data.

Figure 16. FTS SWIR Level 3 global CO2 distribution for November 2009. Blanks in white denote no available data.
Figure 16. FTS SWIR Level 3 global CO2 distribution for November 2009. Blanks in white denote no available data.
Figure 17. FTS SWIR Level 3 global CH4 distribution for November 2009. Blanks in white denote no available data.
Figure 17. FTS SWIR Level 3 global CH4 distribution for November 2009. Blanks in white denote no available data.
Figure 18. CAI Level 3 global radiance distribution obtained between November 19 and 21, 2009. This image was produced by assigning colors (blue, red, and green) for the signals in the bands 1, 2, and 3.
Figure 18. CAI Level 3 global radiance distribution obtained between November 19 and 21, 2009. This image was produced by assigning colors (blue, red, and green) for the signals in the bands 1, 2, and 3.
Figure 19. CAI Level 3 global reflectance distribution (clear-sky) synthesized from cloud-free data obtained between November 1 and 30, 2009. This image was produced by assigning colors (blue, red, and green) for the signals in the bands 1, 2, and 3.
Figure 19. CAI Level 3 global reflectance distribution (clear-sky) synthesized from cloud-free data obtained between November 1 and 30, 2009. This image was produced by assigning colors (blue, red, and green) for the signals in the bands 1, 2, and 3.
Level 4 data products

The Level 4A data product shows monthly CO2 source/sink strengths (fluxes) in 64 global regions that are inversely estimated from the FTS SWIR Level 2 column-averaged mixing ratios and ground-based observational data using a global atmospheric transport model.

The Level 4B data product presents global CO2 concentrations in three dimensions calculated from the Level 4A data product by using the atmospheric transport model. The data product has a horizontal resolution of 2.5x 2.5 and a time step of six hours.