Data Access

Last Update: December 23, 2010

Level 1 and Atmospheres Archive and Distribution System (LAADS) and Data Pools

LAADS provides users with access to any of the following:

• Collection 4 or 5 forward processed atmospheres data products. (Atmospheres Archive and Land Archive).
• Collection 4 and 5 reprocessed atmospheres data products including cloud mask/profiles (Atmospheres Archive).
• Collection 4 products are only available on a processing-on-demand basis. Further capabilty will only be provided until August 2007 when the ESDIS 6-month rule for prior collections is applicable.
• Collection 5 geolocation and cloud mask products.
• Collection 5 L1B products (Atmospheres Archive and Land Archive) through a limited-duration data pool. However, CONUS and European L1B data will be archived in LAADS. At a later date, the Asian region will be added.
• Collection 5 Aeronet Subsetter, Pixel Subsetter, and OBC file ((Special Products).

LAADS provides three types of access:

• LAADSWeb. This provides user access to any data archived in LAADS or the data pools. It enables the user to perform a variety of post processing LAADS Capabilities) including processing-on-demand which will be required for any data pool products for time periods beyond those for which data are maintained on the data pools (Atmospheres Archive and Land Archive). The URL for LAADS Web is http://ladsweb.nascom.nasa.gov.
• Direct access to the LAADS/data pool archives through anonymous FTP. The FTP site is ladsweb.nascom.nasa.gov and directory structure information is provided in the LAADS and Data Pool README.
• A McIDAS server at ladsweb.nascom.nasa.gov enables users of the University of Wisconsin data analysis package to access MODIS products online LAADS archive. More information on McIDAS software is available at http://www.ssec.wisc.edu/mcidas/. Users need to download the package and contact MODAPS User Services at MODAPSUSO@lists.nasa.gov or 1-866-506-6347 (toll free US only) to establish capability.

Compressed L1B files access:

• Many HDF files stored in LAADS and the associated data pools are internally compressed using the NCSA tool "hrepack". This includes the L1B data products stored on the data pools and distributed through subscriptions. This compression is transparent to many user applications. However, in some cases it will be necessary to generate uncompressed L1B files in order to get acceptable performance from applications. Examples of these are running downstream L2 PGEs, McIDAS, and some IDL applications (however, ENVI appears to be transparent).
• hrepack is documented at http://hdf.ncsa.uiuc.edu/tools/hrepack/hrepack.html.
• The hrepack executable can be downloaded from http://hdf.ncsa.uiuc.edu/release4/obtain.html or ftp://ftp.ncsa.uiuc.edu/HDF/HDF/HDF_Current/bin/.
• For usage on Unix or Mac Systems:
  • Be sure to make hrepack executable on your system: chmod +x hrepack
  • An example (csh or tcsh) of Unix/Mac commands to uncompress a Level-1B file;
    set file = MYD021KM.A2006110.1815.2006112085606.hdf
    hrepack -i $file -o $file.unpack -t'*:NONE'
    if ( -e $file.unpack && "$status"== "0" ) mv $file.unpack $file
    
  • If you encounter applications that require un-compression we would appreciate hearing from you at Gang.Ye-1@nasa.gov in order that we can pass the information forward to other users.