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SST record 50 km cell MDS
BT/TOA Sea record 17 km cell MDS
ATS_TOA_1P_MDSR_conf
ATS_TOA_1P_MDSR_cl
ATS_TOA_1P_ADSR_pix
ATS_SST_AX_GADSR
Vegetation fraction for Land Surface Temperature Retrieval GADS
Topographic Variance data for Land Surface Temperature Retrieval GADS
Land Surface Temperature retrieval coefficients GADS
General Parameters for Land Surface Temperature Retrieval GADS
Climatology Variance Data for Land Surface Temperature Retrieval GADS
Level 0 SPH
Level 0 MDSR
Auxilliary Data SPH with N = 1
1.6 micron nadir view MDS
Summary Quality ADS
Scan pixel x and y ADS
Grid pixel latitude and longtitude topographic corrections ADS
Across-track Band Mapping Look-up Table
Configuration Data GADS
Processor configuration GADS
LST record 50 km cell MDS
Distributed product MDS
Level 2 SPH
SPH
10-arcminute mds
Limits GADS
Validation Parameters GADS
BT/TOA Land record 17 km cell MDS
General Parameters GADS
Temperature to Radiance LUT GADS
Radiance to Brightness Temperature LUT GADS
Medium/High Level Test LUT GADS
Infrared Histogram Test LUT GADS
11 Micron Spatial Coherence Test LUT GADS
11/3.7 Micron Nadir/Forward Test LUT GADS
11/12 Micron Nadir/Forward Test LUT GADS
Characterisation GADS
Browse Day_Time Colour LUT GADS
Browse SPH
Grid pixel latitude and longtitude topographic correction ADS
Level 2 SPH
Auxilliary Products
ATS_VC1_AX: Visible Calibration data
ATS_SST_AX: SST Retrieval Coeficients data
ATS_PC1_AX: Level-1B Processing configuration data
ATS_INS_AX: AATSR Instrument data
ATS_GC1_AX: General Calibration data
ATS_CH1_AX: Level-1B Characterization data
ATS_BRW_AX: Browse Product LUT data
Level 0 Products
ATS_NL__0P: AATSR Level 0 product
Browse Products
ATS_AST_BP: AATSR browse image
Level 1 Products
ATS_TOA_1P: AATSR Gridded brightness temperature and reflectance
Level 2 Products
ATS_NR__2P: AATSR geophysical product (full resolution)
ATS_MET_2P: AATSR Spatially Averaged Sea Surface Temperature for Meteo Users
ATS_AR__2P: AATSR averaged geophysical product
Frequently Asked Questions
The AATSR Instrument
Instrument Characteristics and Performance
In-flight performance verification
Instrument Description
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AATSR Products and Algorithms
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Auxiliary Data Sets for Level 2 processing
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The AATSR Products User Guide
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Breakup of the Ross Ice Shelf
Land cover in the Middle East
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Mutsu Bay, Japan
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Spatially Averaged Global SST, September 1993
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Why Choose AATSR Data?
Why Choose AATSR Data?
Special Features of AATSR
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The AATSR Handbook
SST record 17 km cell MDS
Surface Vegetation class for Land Surface Temperature Retrieval GADS
1.6 micron forward view MDS
12 micron nadir view MDS
12 micron forward view MDS
Summary Quality ADS
Surveillance Limits GADS
Master Unpacking Definition Table GADS
1.6 micron Non-Linearity Correction LUT GADS
General Parameters GADS
Thin Cirrus Test LUT GADS
Fog/low Stratus Test LUT GADS
1.6 Micron Histogram
Browse MDS
ATS_CL1_AX: Cloud LUT data
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Payload description, position on the platform
Auxiliary products
Auxiliary Data Sets for Level 1B processing
Summary of auxiliary data sets
Calculate Solar Angles
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Hints and Algorithms for Higher Level Processing
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ATS_TOA_1P_ADSR_sa
Visible calibration coefficients GADS
Level 1B SPH
LST record 17 km cell MDS
Conversion Parameters GADS
12 Micron Gross Cloud Test LUT GADS
ATS_PC2_AX: Level-2 Processor Configuration data
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BT/TOA Sea record 50 km cell MDS
BT/TOA Land record 50 km cell MDS
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2.7.2 Level 2 Products

2.7.2.1 ATS_NR_2P

The Gridded Surface Temperature (GST) Product is the Level 2 full resolution geophysical product. It contains a single MDS 6.6.39. the contents of which are switchable, that is to say, the content of each pixel field will depend on the surface type. Specifically, the contents of the data fields will depend on the setting of the forward and nadir cloud flags and the land flag as shown in Table 2.31 .

Table 2.31 Contents of the Data Fields
Nadir View
Cloud Flag
Forward View
Cloud Flag
Land Flag Nadir Field Combined Field
0 0 0 Nadir only SST Dual-view SST
0 1 0 Nadir only SST 11 µm BT
1 0/1 0/1 CTT
(currently 11 µm BT)
CTH
(currently set to zero)
0 0/1 1 LST NDVI

Each record contains header data followed by three data fields for each pixel. The header fields are the same as those in the level IB product:

  • Nadir time field;
  • Record quality indicator;
  • Spare field; three spare bytes to ensure that subsequent data fields are aligned on a 4-byte boundary;
  • Image scan y co-ordinate.

The three data fields are the confidence word, the nadir field, and the combined field.

The confidence word contains the flags listed in Table. As noted above, the cloud and land flags (bits 4, 5 and 8) within the confidence words determine the contents of the other two fields, which are switchable.

Bit

Meaning if set

0

Nadir-only SST is valid

1

Nadir-only SST retrieval includes 3.7 micron channel

2

Dual-view SST is valid

3

Dual-view SST retrieval includes 3.7 micron channel

4

Pixel is over land

5

Nadir-view pixel is cloudy

6

Nadir-view pixel has blanking pulse

7

Nadir-view pixel is cosmetic fill

8

Forward-view pixel is cloudy

9

Forward-view pixel has blanking pulse

10

Forward-view pixel is cosmetic fill

11

One or both views flagged cloudy by 1.6 micron test (daytime only)

12

Cloud flagged by 11 micron/12 micron nadir - forward test

13

One or both views flagged cloudy by infra-red histogram test

14 - 15

Topographic variance flags for LST retrieval

Note: Bits are numbered from ms bit 15, ls bit 0

Bit 0 is set if the nadir field contains a valid datum, and Bit 2 is set if th ecombined field contains a valid datum. This is true regardless of the surface type. Thus although bit 0 is described as 'nadir only SST is valid' here and elsewhere in the AATSR documentation, this is a misnomer, because it implies that the bit is not used if the pixel is not clear sea. It should properly be called 'nadir image valid' to imply that regardless of surface type the value in the nadir image field contains a valid datum appropriate to the surface type. If the pixel were a land pixel, bit 0 would be set to indicate that the nadir field contains a valid LST. In a similar way bit 2 should be called 'combined image valid', not 'dual view SST is valid'.

(The description 'nadir only SST is valid' is historical; it comes from the SADIST-2 GSST product, which did not have fields whose meaning depended on surface type in the same way. Bit 0 does not have the same meaning in the AATSR product as in the SADIST product.)

Bits 1 and 3 are used only if the pixel is over clear sea and so contains valid nadir-only and dual view SST values. These bits are set to indicate that the 3.7 micron channel data was used in the retrieval of the corresponding nadir-only or dual view SST. (Thus typically these bits will be set for night-time data, but not for data measured during the day.)

Bit 4 is set to indicate a land pixel; it is a copy of the corresponding land flag from the Level 1B product.

Bits 5 – 10 are copies of the corresponding nadir and forward view cloud and confidence flags from the Level 1B product. Bits 11 - 13 are derived from the corresponding Level 1B cloud flags; bit 12 is a copy of the Level 1B 11 / 12 micron nadir-forward cloud test, while bits 11 and 13 are the OR of the nadir and forward view flags for the 1.6 micron and infrared histogram tests.

Finally, bits 14 and 15 form the topographic variance flag for the LST.

The principal annotation data sets from the GBTR product from which the GST is derived are also included in this product. The Annotation Data Sets are as follows.

  • The format of the Summary Quality ADS 6.6.37. is similar to that of the Level 1B product, but contains four additional fields.
  • The remaining ADS are identical to those of the corresponding GBTR product.
  • ADS 1 and ADS 2 are provided so that the original scan positions can be recovered if required.
  • ADS 3 6.6.43. contains grid pixel latitude and longitude.
  • ADS 4 6.6.44. contains scan pixel x and y.
  • ADS 5 and ADS 6 contain solar and viewing angles for pixels in the nadir and forward view respectively.

The structure of this product is shown in the formats 6.1.3. section.

2.7.2.2 ATS_AR_2P

The Averaged Surface Temperature (AST) Product contains averaged geophysical at two different resolutions, and with respect to two different averaging schemes. Measurement data sets at resolutions of 0.5° by 0.5° and 10 by 10 arcmin with respect to a latitude/longitude grid provide continuity with existing ATSR-2 products. Other data sets contain data averaged over equal area cells of 50 by 50 km and 17 by 17 km aligned with the satellite ground track. Both top-of-atmosphere and surface data sets are provided. The surface temperature data sets provide, for sea cells, nadir and dual view sea surface temperatures, and for land cells, land surface temperature (currently set to the 11 µm BT) and NDVI. Cloud data is also included. No ADS are included in the AST product; auxiliary data is contained within the MDS. The data sets of the AST product are arranged by surface type and resolution as shown in the formats 6.1.1. section.

Because the cells and sub-cells are defined with respect to their geographic co-ordinates, there is no simple relationship between the cell positions and the satellite ground track. There is therefore no unambiguous natural way to order the cells and sub-cells in the output product. Also the edges of the cells are not in general parallel to the instrument swath, and cells may be intersected by the swath edge. Thus they may no contain complete data.

The AST product contains 8 MDS at 10 / 30 arc minute resolutions, comprising Surface Temperature and Brightness Temperature / Reflectance MDS for each resolution and for each surface type (land and sea).

The basic unit is the 30 arc minute cell. If any pixel falls within the bounds of a 30 arc-minute cell, a data structure is created for this cell, and this will contain sub-structures for each of the nine 10 arc minute sub-cells contained in the cell, into which will be assembled all the relevant data for the 8 MDS. The algorithm for output of the data then provides as follows.

  • If a 30 arc minute cell contains any data, a record corresponding to this cell will be output to each 30 arc minute MDS, and records corresponding to each of the nine 10 arc minute sub-cells will be output to each of the 10 arc minute MDS.

Although the 30 arc minute cell contains data, there may not be any valid pixels to contribute to particular sub-cells or MDs records. For example:

  • If a cell consists entirely of land pixels, there will be not data in the corresponding sea records (and vice versa).
  • If a 30 arc minute cell is intersected by the swath edge, some of the sub-cells may fall outside the swath, and contain no measured pixels. In this case the 10 arc minute MDS records corresponding to these sub-cells will contain no valid data.

The Record Quality Indicator is used to flag cells which contain no pixels of the corresponding surface type. (The Attachment Flag is not used in the AST product because there are no ADS, and no definition of a granule.) In addition, other exception values will appear in the relevant data fields.

The basis of the Record Quality Indicator setting is as follows. For each 10 arc minute sub-cell the processor calculates the total number of pixels in each view, and in each of the categories defined by the land/sea and cloud/clear flags that fall within the sub-cell. From these one can calculate the total number of land and sea pixels in each view that fall within the sub-cell. (Note that the two views would give identical counts if we are dealing with land and sea pixels, since the pixels in the views are co-located. But this may not be true if there are different numbers of unfilled pixels in the two views.) The record Quality Indicator is then set if the corresponding count in each view is zero. (In this case of course all the data will contribute to the corresponding land MDS.)

Spatially averaged quantities, averaged over cells and sub-cells of nominal dimensions 50 km by 50 km and 17 km by 17 km respectively, are derived to give an alternative averaged product based on equal area cells. The relationship between the cells and the swath is simpler in this case, since the cell boundaries are parallel to the instrument swath, but the same principles of data selection apply.

The AST confidence flags are shown in Table 2.32 . Currently only four flags are used. Bits 0 and 1 are used only for the Sea records, and are set to indicate that the 3.7 micron channel data was used in the retrieval of the nadir-only or dual view SST. (Thus typically these bits will be set for night-time data, but not for data measured during the day.)

Bits 2 and 3 are set to indicate that the nadir and forward views respectively contain day-time data, and thus that the nadir only and dual view SST retrievals will include such data. Clearly it will generally be the case that these bits will be set when bits 0 and 1 are clear, and vice versa, although this is not an invariable rule.)

Table 2.32 AST confidence word

bit

meaning if set.

0

Sea MDS: Nadir-only SST retrieval used 3.7 micron channel

Land MDS: Reserved

1

Sea MDS: Dual-view SST retrieval used 3.7 micron channel

Land MDS: Reserved

2

Nadir view contains day-time data

3

Forward view contains day-time data

4 - 31

Unused

2.7.2.3 ATS_MET_2P

The Meteo product is a fast delivery product designed for use by meteorological offices, and contains averaged BT and SST at 10 arc minute resolution. The single MDS 6.6.35. of this product comprises the fields of MDS#3 (SST record, 10 arc min cell) of the AST product, with the addition of Average Brightness Temperature (ABT) fields (BT/TOA sea record, 10 arc min cell) to make it more self-contained.

The structure of this product is shown in the formats 6.1.2. section.

In the AST product (from which the Meteo product is derived), all cells are present regardless of surface type. Specifically every 10 arc minute cell is represented by two records - a land record and a sea record, and all are physically present even if they are empty (e.g. land records for cells that are entirely sea, and vice versa). If a cell is entirely over sea, the sea record will contain valid data, and the land record will not. If a cell is intersected by coastline then both records will contain valid data, representing / derived from the averaged brightness temperatures of the land and sea pixels respectively.

The Meteo product contains only the sea records, but it contains all of them, including those that are wholly over land (which are empty) or partly over land (which contain averages derived from only the sea pixels in the cell).