Long-term Data Record

The Long-Term Data Record (LTDR) project was originally funded through a NASA REASoN program in 2002, and later via a MEaSUREs project in 2010.  Currently, LTDR is being funded by a new MEaSUREs 2017 project besides the Climate Data Record Program from the NOAA National Climatic Data Center.  With Eric Vermote as its Principal Investigator, this project continues to produce and distribute a global land surface climate data record (CDR) that is critically important to studying global climate change.  The LTDR project is unique in that it serves as a bridge that connects data derived from the NOAA Advanced Very High Resolution Radiometer (AVHRR), the EOS Moderate resolution Imaging Spectroradiometer (MODIS), the Suomi National Polar-orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite (VIIRS), and Joint Polar Satellite System (JPSS) VIIRS missions. Starting from the 1980s decade, such a wide temporal extent helps offer data products that span four decades.

Long-term Data Record


Long-term Data Record The LTDR project produces, validates and distributes a global land surface CDR that uses both mature and well-tested algorithms in concert with the best-available polar-orbiting satellite data from past to the present. The LAADS DAAC hosts the LTDR collections that include top-of-atmosphere reflectance, surface reflectance and vegetation index products. The LTDR project currently leverages AVHRR, MODIS, and VIIRS data sources. LTDR draws from the following eight AVHRR missions: NOAA-7, NOAA-9, NOAA-11, NOAA-14, NOAA-16, NOAA-18, NOAA-19 and MetOp-B.1 Currently, the project generates a daily surface reflectance product as the fundamental climate data record (FCDR), and derives daily Normalized Differential Vegetation Index (NDVI) and Leaf-Area Index/fraction of absorbed Photosynthetically Active Radiation (LAI/fPAR) as two thematic CDRs (TCDR). LAI/fPAR was developed as an experimental product.

LTDR uses the best-available data, addressing the dynamic data continuity of the input observations from AVHRR and MODIS with different spatial resolutions that include the following:

  • AVHRR Global Area Coverage (GAC): 4 km (1981 – present)
  • AVHRR High Resolution Picture Transmission (HRPT): 1 km (1992 – 1998)
  • AVHRR Local Area Coverage (LAC): 1 km (1992 – 1998)

The GAC data products from the AVHRR sensors onboard the NOAA satellites from 1981 – present are reprocessed by applying the preprocessing improvements identified in the AVHRR Pathfinder II project, and the atmospheric corrections used in the MODIS preprocessing. The project compares the AVHRR results with MODIS products where the two instruments overlap in time (from 2000 on for Terra/MODIS, and from mid-2002 for Aqua/MODIS). Gaps in the data record from these two instruments are filled using a 1-km SPOT VEGETATION surface reflectance product generated by the European Geoland2 project.

1 Apart from the unsuccessful missions described in the first paragraph, data from other NOAA missions were not used primarily due to their performance degradation issues.


The primary aim of the LTDR project is to produce, validate and distribute a global land surface climate data record (CDR) using a combination of mature and well-tested algorithms, and the best available polar-orbiting satellite data from the past to the present.  When the LTDR project started, the data record started with the NOAA AVHRR through the EOS MODIS missions, and now, in 2020, continues into the SNPP and JPSS VIIRS missions as well.  LTDR’s portfolio consists of one fundamental climate data record (FCDR), the surface reflectance product, and two thematic CDRs (TCDR) derived from the FCDR that include the Normalized Difference Vegetation Index and Leaf-Area Index/fraction of absorbed Photosynthetically Active Radiation.


The LTDR project’s TCDRs, NDVI and LAI/fPAR are important Essential Climate Variables (ECV) as deemed by the Global Climate Observing System of the World Meteorological Organization, and are used extensively for climate change research.  Its products constitute a consistent climate data record of the land surface from 1981 through the present.

Output products

LTDR products table

Short-name Long-name
Nxx2_AVH02C1 NOAA-xx AVHRR Top-of-Atmosphere Reflectance Daily L3 Global 0.05 Deg CMG
Nxx_AVH09C1 NOAA-xx AVHRR Atmospherically Corrected Reflectance Daily L3 Global 0.05 Deg CMG
Nxx_AVH09C1_NC NOAA-xx AVHRR Atmospherically Corrected Reflectance Daily L3 Global 0.05 Deg CMG NetCDF
Nxx_AVH13C1 NOAA-xx AVHRR Atmospherically Corrected NDVI Daily L3 Global 0.05 Deg CMG
Nxx_AVH13C1_NC NOAA-xx AVHRR Atmospherically Corrected NDVI Daily L3 Global 0.05 Deg CMG NetCDF
Nxx_AVH15C1_NC NOAA-xx AVHRR Atmospherically Corrected LAI and fPAR Daily L3 Global 0.05 Deg CMG NetCDF 

LTDR product information

Short-names Nxx_AVH02C1, Nxx_AVH09C1, Nxx_AVH13C1Nxx_AVH09C1_NC, Nxx_AVH13C1_NC, Nxx_AVH15C1_NC
Long-names Refer to LTDR Products Table above
Platforms NOAA-7, NOAA-9, NOAA-11, NOAA-14, NOAA-16, NOAA-18, NOAA-19, MetOp-B
Processing Level Level-3
Spatial Resolution 0.05 Deg.
Temporal Resolution Daily
Production Frequency One per day
File Sizes (Average) AVH02C1: 150 MBAVH09C1: 180 MBAVH09C1_NC: 120 MBAVH13C1: 30 MBAVH13C1_NC: 60 MBAVH15C1_NC: 10 MB
Data Formats HDF4, NetCDF4
File Naming Convention AVH09C1.AYYYYDDD.Nxx.CCC.YYYYDDDHHMMSS.hdf·       AVH09C1: Short-name·       AYYYYDDD: Acquisition Year and Day of Year (Julian Calendar)·       Nxx: AVHRR instrument number·       CCC: Collection version·       YYYYDDDHHMMSS: Production Date – Year, Day, Hour, Minute, Second·       hdf: Data format
Dataset Originator/Creator MODIS Adaptive Processing System (MODAPS)

2 Nxx refers to specific AVHRR instruments that may range from N07 (for NOAA-07 that was launched June 1981) through N19 (for NOAA-19 that was launched February 2009).

Project documentation

LTDR IGARSS 2007 paper LTDR paper presented at the 2007 IGARSS
AGU Fall 2009 presentation LTDR presentation at the 2009 Fall AGU
IGARSS 2007 presentation LTDR presentation at the 2007 IGARSS
LTDR Montana Veg. Workshop LTDR presentation, 2006 Global Veg. Workshop, MT
AGU Fall 2005 presentation LTDR presentation, NPOESS session, 2005 Fall AGU
MODIS STM 2004 presentation LTDR presentation, MODIS Sci. Team Meeting, 2004
LTDR 2007 Workshop LTDR presentations, 2007 Workshop, College Park, MD
LTDR V5 User Guide LTDR AVHRR V5 Products User Guide, 2021

Citation Information

If you happen to incorporate LTDR products in your research, please use the following acknowledgment within your published work:

“These data products are processed and distributed by the MEaSUREs Long-Term Data Record project by the Level-1 and Atmosphere Archive & Distribution System (LAADS) Distributed Active Archive Center (DAAC) at the Goddard Space Flight Center.”  If possible, please e-mail or send us reprints/citations of papers or oral presentations that are based on LTDR products (see below for email and mailing address). This will help us to stay informed regarding how our data are being used.

There are no restrictions for use of data from the LTDR project unless otherwise expressly stated. If you have any questions, please contact us.

Related Links

Long-term Data Record