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AVHRR Vicarious Calibration

LTDR Product Documents

LTDR Version History

Data Download

Global Browse Images:

Quality Assessment

Publication and Presentations

Team Members


The LTDR V5 forward production will be switched from the AVHRR instrument onboard N19 to the same from MetOp-B, in a month, and this will be followed up by a re-processing of all the LTDR records from the beginning of the MetOp-B mission, in V5. (click here for the details)

V5 and V4 LTDR data now available. V3 LTDR has been decommissioned

Data Download

The LTDR data can now be obtained from LAADS, via a HTTPS protocol. The URL from which data can be obtained looks like this:[AS]/[ESDT]/[year]/[julian day]/


AS = archive set, which would be 464 for Version 4 data and 465 for Version 5 data.

ESDT = N11_AVH02C1 for L1B, N07_AVH09C1 for surface reflectance, N09_AVH13C1 for NDVI etc. Note: the NXX represents the NOAA AVHRR sensor ID. The following link goes into detail regarding how to get the data:

To summarize: If you are not already a registered user of LAADS, create a profile with Earthdata ( Connect to LAADS archive and generate App keys (under the menu profile). App keys are tokens that identify you, and they get put into HTTP GET commands when downloading the data. The above website explains all that in more detail. That website also gives examples of scripts (in Perl, bash, or Python) that can be used to download data. Here are additional perl and python scripts that you could use to download the LTDR data

The product file formats are described in the LTDR Data Format Description


  • Data records for some of the data days of V5/V4 are removed from the archive due to geolocation errors or bad data quality, though the browse images are presented on the global browse web page.
  • V5/V4 LTDR data is available for the period from 1981 to current from the reprocessing of the N07-N19 AVHRR data. Processing and distribution of LTDR records from N16 and N18 for years after 2006 and 2009 respectively were discontinued. N16 data was impacted by significant data gap and serious noise from the on-board scan motor problem, and N16 data had loss of coverage for northern hemispheres resulting from drift in the equator crossing time.


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