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Natural Environment Research Council
   
   
Fact Sheet: AATSR
 

(A)ATSR Multimission Archive
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Introduction

A major activity is currently underway at the NERC Earth Observation Data Centre (NEODC) at RAL to produce a 15-year archive of high-quality sea-surface temperature and image products from the (A)ATSR series of instruments in a common format.

ral,nerc,decc,esa logos

Using a conversion tool produced at RAL, the entire dataset of ATSR-1 and -2 UBT products has been processed to produce ENVISAT-compatible Level 1b, Level 2 and METEO products, which populate the archive alongside the equivalent set of products from AATSR. The dataset is now part of the NEODC archive, with L1b and L2 products from all 3 missions already available in ENVISAT format. AATSR-format outputs of this project have been duplicated to ESA for inclusion in its own archive which will serve the international community. The project is a joint venture involving ESA, the UK Department of Energy and Climate Change (DECC), Natural Environment Research Council (NERC) and STFC/RAL.

The Advanced Along Track Scanning Radiometer (AATSR) was built by Astrium, subsequently calibrated and characterised at the Rutherford Appleton Laboratory, and continues the ATSR-1 and ATSR-2 mission data sets of precise sea surface temperature (SST), thereby ensuring the production of a 15 year near-continuous data set from the ERS-1, ERS-2 and ENVISAT missions at the levels of accuracy of 0.3 K or better for climate research. AATSR was launched on board the Envisat satellite on 1st March 2002. ATSR-1 and 2 are described in more detail on the ATSR-1/2 fact sheet. For more details on Envisat and its other instruments see the Envisat fact sheet.

AATSR has the same signal channels and embodies exactly the same viewing principle as ATSR-2. These are: thermal channels at 3.7, 10.8, and 12 microns wavelength; and reflected visible/near infrared channels at 0.555, 0.659, 0.865, and 1.61 microns wavelength. Like its predecessors, ATSR-1 and ATSR-2, AATSR has on-board calibration systems for the thermal channels, using two black bodies, viewed every scan, and for the visible channel a sample of solar radiation scattered from a diffuser plate is viewed once per orbit. Unlike ATSR-2 it maintains full digitisation of all channels all the time and has no limited-data-rate operating modes.

For the latest information see http://envisat.esa.int/.

Click image for larger version
Fig. 1 Flight model of AATSR. Image from http://envisat.esa.int

For more details about AATSR see http://www.atsr.rl.ac.uk/ and http://envisat.esa.int/instruments/tour-index/aatsr/.

Platform Parameters

Launch date 1/03/2002
Status / projected mission lifetime > 5years
Orbit parameters 30 km in front of ERS2
Nominal altitude 800 km : same as ERS2, near circular
Orbit type near-polar, sun-synchronous
Inclination 98.55 ?
Repeat period 35 days
Equatorial crossing time 10:00 local time (descending node)
Swath width various
Resolution various
Special features

Data availability

NEODC
Availability fof (A)ATSR products in the NEODC (A)ATSR archive is shown in the table below. Click the link foreach mission to browse products in the archive and (if authorised) download via HTTP. The same directory structure is also available via ftp at ftp.neodc.rl.ac.uk starting with drectory /neodc/aatsr_multimission/.
(A)ATSR product availability
Mission Level 1b Level 2 METEO Current coverage
AATSR
Yes
Yes
Yes
2002 - present. Diagram (pdf)
ATSR-2
Yes
Yes
Yes
1995 - June 2003. Diagram (pdf)
ATSR-1
Yes
Yes
Yes
1991 - 1997. Diagram (pdf)

ESA
For currently available information about ENVISAT data products and availability, see http://envisat.esa.int/dataproducts/.

Version 2.0 Products

During 2008, harmonisation and re-processing efforts have created a new set of products, now available in the archive. The following information summarises the changes:

AATSR v2.0

Archive products have been reprocessed by ESA to match the current version (IPF v6.01) of the AATSR Operational Processor.
AATSR v2.0 improvements
28 March 2007 IPF v6.0 IPF 6.0 includes improvements to the LST algorithm and cloud clearing tests
The improvement of the performance of the cloud clearing tests over land
An improved treatment of pixels in areas of marginal cloud
LST retrieval over inland lakes
Spatially averaged LST retrieval
23 June 2007 IPF v6.01 (used for v2.0 processing) Corrects for an erroneous calculation of the ANX during consolidated processing, leading to mission Viscal GADS in the L1b product.
The improvement of the performance of the cloud clearing tests over land

For further details, please consult the technical documentation available from the ENVISAT website, in particular

ATSR-1/2 v2.0

ATSR-1, 2 : The RAL Archive Product Processor (APP) has been updated to align with the ESA Operational Processor/IPF and both missions reprocessed with the new processor.

Issue ATSR-1/2 v2.0 Level 1b improvements
001 Forward-view Solar angles in 1st 2 frames of L1b (and therefore L2) products (fixed)
002 Incorrect number of DSDs in MPH (fixed)
003 Forward view blanking-pulse flags (fixed)
009 APP L1b processing updated to match IPF extended cloud flagging
010 Snow flag bug in extended cloud-flagging scheme (fixed)
013 ATSR-1 NDVI and NSDI tests should be switched off due to no visible channels (fixed)

Issue ATSR-1/2 v2.0 Level 2 improvements
005 AST confidence word does not flag 3.7u used in SST retrieval (fixed)
006 AST confidence word fixed to match the IPF rather than the original specification (fixed)
007 LST values in L2 averaged product invalid (fixed)
008 Yaw correction flag not set in PROC_CENTER field of METEO (fixed)
011 30 arcmin SST MDS in AR product has anomalous content in 3 fields ; Std Dev of DV-SST, CTT/FRWRD, PCC/FRWRD (fixed)
012 AR and NR products have unfilled "Referencing DSD" for LST auxdata (fixed)

Further Information

ENVISAT
ESA website: ENVISAT main page
ENVISAT data format specification documents
ENVISAT product status including important product disclaimers
AATSR
ESA website: AATSR instrument
ESA website: AATSR product handbook
University of Leicester : AATSR project page
ERS Mission
ESA website: ERS Missions

Documents
ATSR Product user guide (RAL)
ATSR Image FAQ (RAL)
Current SPRs (software problem reports) detailng known issues with the RAL Archive Product Processsors for ATSR-1/2
Technical note (draft) describing differences between ENVISAT-format products ATSR-1/2 and AATSR products.
ER-RP-OXF-AT-0001.pdf Atsr-1 test and calibration report ER-RP-OXF-AT-OOOI (G. Mason, 1991)
ER-RP-OXF-AT-2001.pdf Atsr-2 test and calibration report ER-RP-OXF-AT-2001 (D.L. Smith, R.E.J. Watkins & D.R. Corney, 1993)
Auxiliary files used to produce (A)ATSR archive products
PO-TR-RAL-AT-0024 (pdf) AATSR Infra-Red Radiometric Calibration Report (D.L. Smith, 1999)
PO-TR-RAL-AT-0023 (pdf) AATSR Visible Calibration Report (D.L.Smith, 1999)
PR-TN-RAL-AT-0538 (pdf) Technical Note : Updates to AATSR In-Band Solar Irradiances (D.L.Smith, 2004)
(A)ATSR-related documents in CEDA document repository CEDA (NEODC/BADC) maintains a document respository into which it has started to add dataset-related technical information, including AATSR user bulletins and similar documentation
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