US Government security requirements no longer permit CDDIS to offer data via traditional unencrypted anonymous ftp; this service was discontinued on October 31, 2020. All data are still available, however access must be via HTTPS or ftp-ssl.

Instructions with examples and our FAQ can be found at: https://cddis.nasa.gov/Data_and_Derived_Products/CDDIS_Archive_Access.html.

If you still have difficulty after reading and attempting the examples on that page, please contact us at support-cddis@earthdata.nasa.gov.

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About the CDDIS SLR data and products archive

Data archive

Laser ranging data consist of a distance or range (round-trip, station to satellite and back) and time, together with data correction information such as atmospheric effects, which are to be applied to the data. Raw laser ranges are formatted at the remote station before transmission to operational data centers where the data are translated into the appropriate format.

The CDDIS serves as a global data center for the International Laser Ranging Service (ILRS). ILRS Operations Centers interface to SLR stations, collecting, validating, and merging data from selected stations. At a minimum, laser stations forward their data to operations/data centers on a daily basis where they are merged into files by day and satellite for transmission to and archive at the global data centers such as the CDDIS.

Laser ranging stations use short-pulse lasers and state-of-the-art optical receivers and timing electronics to measure the two-way time of flight (and hence distance) from ground stations to retroreflector arrays on Earth-orbiting satellites and the Moon.
Laser ranging stations use short-pulse lasers and state-of-the-art optical receivers and timing electronics to measure the two-way time of flight (and hence distance) from ground stations to retroreflector arrays on Earth-orbiting satellites and the Moon.

Product archive

Products derived from SLR data are under development by the ILRS Analysis Working Group. These products include station positions and Earth orientation parameters (EOP) and are located on the CDDIS in subdirectories by data type at https://cddis.nasa.gov/archive/slr/products.