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AATSR Data Formats Products
SST record 50 km cell MDS
BT/TOA Sea record 17 km cell MDS
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
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
Internal Data Flow
Instrument Functionality
AATSR Products and Algorithms
Common Auxiliary data sets
Auxiliary Data Sets for Level 2 processing
Instrument Specific Topics
Level 2 Products
Level 1B Products and Algorithms
Level 1B Products
Instrument Pixel Geolocation
The Level 0 Product
Differences Between ATSR-2 and AATSR Source Packets
Definitions and Conventions
Organisation of Products
Relationship Between AATSR and ATSR Products
AATSR Product Organisation
Data Handling Cookbook
Characterisation and Calibration
Monitoring of AATSR VISCAL Parameters
Latency, Throughput and Data Volume
Data Processing Software
Data Processing Centres
The AATSR Products User Guide
Image Gallery
Breakup of the Ross Ice Shelf
Land cover in the Middle East
Typhoon Saomai
Mutsu Bay, Japan
Deforestation in Brazil
Spatially Averaged Global SST, September 1993
Further Reading
How to use AATSR data
Why Choose AATSR Data?
Why Choose AATSR Data?
Special Features of AATSR
Principles of Measurement
Scientific Background
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
Pre-flight characteristics and expected performance
Payload description, position on the platform
Auxiliary products
Auxiliary Data Sets for Level 1B processing
Summary of auxiliary data sets
Calculate Solar Angles
Image Pixel Geolocation
Level 0 Products
Acquisition and On-Board Data Processing
Product Evolution History
Hints and Algorithms for Higher Level Processing
Data Volume
Software tools
Summary of Applications vs Products
Geophysical Coverage
Geophysical Measurements
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
Level 2 Products
Hints and Algorithms for Data Use
BT/TOA Sea record 50 km cell MDS
BT/TOA Land record 50 km cell MDS
Level 2 Algorithms
Signal Calibration
Site Map
Frequently asked questions
Terms of use
Contact us


2.3 Definitions and Conventions

2.3.1 Definitions

Across-track band: The instrument swath is imagined as divided into 10 bands of width 50 km parallel to the ground track. The bands are symmetrically arranged on either side of the ground track, so that for example Band 0 covers the range -250 < x < -200 km, and Band 5 covers the range 0 < x < 50 km. Historically these were originally defined as part of an earlier ATSR SST retrieval algorithm. In this role they are now obsolete, but the structure of the across track bands are still used internally by processor, in particular in relation to the cloud clearing algorithms, and the solar and viewing angles are sampled at the band edges.

Cell (AST): An area spanning 0.5 degree in latitude by 0.5 degree in longitude or 50km by 50km depending on the data set in question, within which pixels contribute to the averaged product.

Granule: A subdivision of the AATSR image. In general 1 granule corresponds to 32 image rows, although the Summary Quality ADS is based on a 512 row granule. In general, a granule is a group of consecutive records in a Measurement Data Set; the number of such records is instrument dependent. Thus for the AATSR full resolution products, the granule is 32 records. It is intended to be the minimum increment used to define the limits of a child product. With the exception of the Summary Quality ADS, all Annotation Data Sets in the AATSR products contain 1 record per granule.

Image pixel: Image pixels are samples of the full resolution product.

Image row: A row of image pixels orthogonal to the satellite ground track. AATSR images are regridded onto a rectangular grid of image pixels centred on the satellite ground track. The image row comprises 512 image pixels.

Instrument pixel: The AATSR scan mirror rotates clockwise (as seen from above) at a uniform rate of 400 revolutions per minute, and so making one rotation in 150 ms. The instrument channels are sampled 2000 times per rotation at equal intervals of time. The instrument thus measures 2000 instrument pixels at equal angular intervals around the scan. Not all of these samples represent a valid measurement, however, since for parts of the scan the instrument is observing parts of the instrument housing.

For this reason not all of these samples are returned in the telemetry. The instrument source packet contains 974 samples (instrument pixels) in 5 groups of contiguous pixels corresponding to the 5 views; VISCAL, nadir view, +X black body, forward view, -X black body (section 3.1.3. and figure3.8 ).

Pixel selection map The pixel selection map defines which of the 2000 pixel samples are actually transmitted to the ground. Strictly it is an array within the DEU with an entry for each pixel to indicate whether or not to format science data for that pixel (Reference: AATSR Instrument Measurement Data Definition Ref. [1.4 ] , PO-TN-MMB-AT-0038). It is possible to update the pixel selection map in flight by macrocommand.

The pixel selection map in use, which is required to unpack the pixel counts in the ground processing, is defined by parameters in the auxiliary data block of the instrument source packet. These parameters are as follows.

Table 2.4 Auxiliary data items defining the pixel selection map
Telemetry mnemonic Telemetry identifier Telemetry description
A2200 IDF20 Pixel Map Readout (VISCAL Start pixel number)
A2210 IDF21 Pixel Map Readout (VISCAL End pixel number)
A2220 IDF22 Pixel Map Readout (Nadir Start pixel number)
A2230 IDF23 Pixel Map Readout (Nadir End pixel number)
A2240 IDF24 Pixel Map Readout (+XBB Start pixel number)
A2250 IDF25 Pixel Map Readout (+XBB End pixel number)
A2260 IDF26 Pixel Map Readout (Along Track Start pixel number)
A2270 IDF27 Pixel Map Readout (Along Track End pixel number)
A2280 IDF28 Pixel Map Readout (-XBB Start pixel number)
A2290 IDF29 Pixel Map Readout (-XBB End pixel number)

Since pixel numbering is contiguous in each scan section, it is always possible to determine the pixel number of a given pixel in any of the scan sections from these values. (Pixel numbering starts at 1 rather than 0.)

The default pixel selection map includes 555 nadir view pixels, 371 forward view pixels, sixteen pixels for each of the two black bodies, and sixteen VISCAL pixels.

Instrument scan: The locus of the line of sight of the scan mirror on the Earth's surface. It is the intersection of the scan cone with the surface, and is approximately elliptical in shape. An instrument scan corresponds to a single telemetry source packet in the Level 0 data.

Sub-cell (AST): An area spanning 10 arc minutes of latitude by 10 arc minutes of longitude or 17km by 17km depending on the data set in question, within which pixels contribute to the averaged product. A sub-cell is one-ninth of an AST cell (q.v.). The sub-cells within each cell are identified by an index in the range 0 to 8 as follows:

Table 2.5 Sub-cell indices within a cell
6 7 8
3 4 5
0 1 2

Unfilled pixel: An image pixel to which no instrument pixel is mapped by the regridding and cosmetic fill processes. Unfilled pixels fall outside the image swath, or beyond the limits of the instrument data that contributed to the product. This is a purely geometrical property of the pixel. Thus an unfilled pixel is to be distinguished from an invalid pixel; the latter is associated with an invalid measurement, while an unfilled pixel is not associated with any measurement.

Definition of cell and sub-cell: To be completed