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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SLR product holdings

Products derived from SLR data archived in the CDDIS support scientific research in:

  • Terrestrial reference frame (center of mass and scale)
  • Improve understanding of the dynamics and modeling of GNSS orbits (one of our major users)
  • Calibration and validation of ocean and ice altimetry missions
  • Static and time-varying gravity field (low order/degree terms)
  • Plate tectonics and crustal deformation
  • Earth orientation and rotation (polar motion, length of day)
  • Total Earth mass distribution
  • Space science – satellite dynamics, etc.
  • Relativity and lunar science

The CDDIS archive of laser ranging products consists of solutions derived by analysis centers in support of the ILRS. The ILRS combination centers retrieve these solutions and produce the combined ILRS A and B solutions (generated by the primary and backup ILRS combination centers, respectively). Products derived from these SLR observations include precise satellite ephemerides, station positions and velocities of sites in the ILRS network, and EOPs (polar motion and rates, length-of-day). ILRS analysis and combination centers deliver the precise orbit and station position/EOP products to the ILRS data centers, including the CDDIS.

Spatial coverage

Temporal coverage

  • SLR station position, and EOP products since June 1976
  • SLR precise satellite orbit products since February 2016

Data formats

Related resources