On 31 October 2020, anonymous ftp access will officially be discontinued at CDDIS. Beginning October 1, 2020, CDDIS will bandwidth limit ALL IPs using anonymous ftp to just 50KB/s and will limit simultaneous downloads to only 3 per IP address. CDDIS is STRONGLY recommending all users begin to transition to using alternate method of access to the CDDIS archive. Examples of alternate methods can be found at: https://cddis.nasa.gov/Data_and_Derived_Products/CDDIS_Archive_Access.html.

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Reference frame products

The CDDIS archive of laser ranging products consists of solutions derived by analysis centers in support of the ILRS. 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 centers deliver the station position/EOP product to the ILRS data centers, including the CDDIS. 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) which are in turn archived in the CDDIS. Prior to 2012, ILRS analysis centers generated the products on a weekly basis; today, these products are generated daily. Station positions and EOP date from 1976 through the present. SLR products are available from the CDDIS in subdirectories by year and date.

Product formats:

  • Software INdependent EXchange (SINEX) format

The starting directory for these files is:

Anonymous ftp service will be discontinued on October 31, 2020.

Append the following directory and file names to the starting directory:


as described in the table below.

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Analysis CenterCode
Bundesamt für Kartographie und Geodäesie (BKG) Germanybkg
Deutsches Geodätisches Forschungsinstitut (DGFI) Germanydgfi
ESA/ESOC, Germanyesa
Groupe de Recherche en Géodésie Spatiale (GRGS) Francegrgs
Helmholtz Centre Potsdam German Research Centre for Geosciences (GFZ), Germanygfz
ILRS primary combination solution ilrsa
ILRS backup combination solutionilrsb
Italian Space Agency, Centro de Geodasia Spaziale "G. Colombo" (ASI/CGS), Italy afi
Joint Center for Earth System Technology/Goddard Space Flight Center (JCET/GSFC) Greenbelt, Maryland, USA jcet
NERC Space Geodesy Facility (NSGF) formely RGO Satellite Laser Ranging Group, United Kingdom ngsf

More about ILRS Analysis Centers

Code Meaning
YYYY 4-digit year
YY2-digit year
MM2-digit month
DD 2-digit day
ACNAMEAnalysis Center Name
### version of solution
TYP type of solution (SNX or SUM)
Z UNIX compressed file