MEMORANDUM

From     :	S. Procter	Document Ref     :	aep_mem_127
To          :	AATSR Contacts List	Date                    : Issue                   : File ID                 :	19 February 2007 1 AEP_MEM_127.doc

SUBJECT      : Sixth AATSR Users Bulletin

Change to Visible Channel Drift Correction

Studies of the long term stability of the AATSR visible channel calibration have shown that the drift does not follow a linear trend as previously supposed. A further correction is therefore needed to compensate for the deviation from the expected trend. Inspection of the data suggests that the calibration drift may be due to the gradual build up of a thin contaminant film on the optical surfaces of the visible calibration system, rather than by the gradual degradation of the exposed optics. A simple thin film model has been applied to the data that appears to confirm this hypothesis. A new drift correction based on this model is proposed in the AATSR Technical Note: Update on AATSR Visible Channel Long Term Trends (PO-TN-RAL-AT-0552), D. Smith, Issue 1.0, 16 January 2006, distributed with this bulletin. A guide to applying the new systematic drift correction to AATSR L1b data is given at the end of this technical note.

In response to these findings, the AATSR Quality Working Group recommended that the visible channel calibration auxiliary file (ATS_VC1_AX) should be updated to include the modified correction. As a result, please note that all AATSR data acquired from 19 December 2006 onwards will contain the new systematic correction for visible channel drift.

Data acquired prior to 19 December 2006 does not contain this new correction. This should be addressed during the second reprocessing of the AATSR data set, planned for Spring 2007. In the meantime, users can correct their historical data themselves using the guide provided in the Appendix of the above technical note.

Any questions on this issue should be directed to aatsr@dpqc.org in the first instance.

IPF 5.6 Update

On 18 January 2007 a patch was applied to the AATSR IPF software; the new version number is 5.60. The patch was to correct for two previously identified problems in the software: inconsistent values in AST confidence word and cloud flagging errors leading to bands of missing data in AATSR consolidated data. Further information is contained in Cyclic Report 54, available from: http://earth.esa.int/pcs/envisat/aatsr/reports/cyclic/.

Orbital VC1 files

As of 01 February 2007 VC1 files are being generated on a more frequent basis, with a validity range of one orbit; the once per day files will continue to be disseminated alongside the orbital files. These files will be available for the consolidated processing of AATSR data and will lead to improved visible calibration performance.

Disabling of some tests in AMALFI

The tests “AATSR SPH Latitude values consistency” and “AATSR SPH Longitude values consistency” are generating a large number of AMALFI failures with child products due to problems with the child product generation software. Until these problems have been remedied the tests have been set to pre-operational. Please note that failure of these tests does not impact on the geolocation data quality as the values in the SPH are meant for information only.

Handbook Amendments

Version 2.0 of the AATSR handbook, launched in May 2006, is intended to remain static. Any updated or additional information produced after Version 2.0 shall be published as separate amendments. These additions can be accessed from the AATSR handbook page, http://envisat.esa.int/handbooks/, as PDF documents. Currently these include the technical notes on the new visible channel drift correction and the latitude dependent correction, circulated as the fifth Users Bulletin.

Envisat Symposium Reminder

The next Envisat Symposium will take place between 23 – 27 April in Montreux, Switzerland.

The main objective of the Symposium is to present the results of exploitation of the ESA EO missions by:

·         providing a forum for investigators to present results of on-going research project activities using ENVISAT, ERS and ESA Third Party missions data;

·         reviewing the development of applications and services;

·         presenting the Global Monitoring for Environment and Security Service Element (GSE);

·         presenting the use of EO in support of International Environmental Conventions.

In addition, the Symposium will provide an opportunity to present future ESA and national EO missions.

 

Further information can be found at http://www.congrex.nl/07A03/