National Aeronautics and Space Administration

The products derived from systems in the NASA Space Geodesy Project are primarily generated as part of NASA’s support of the IAG Services:

• International Laser Ranging Service (ILRS)
• International VLBI Service for Geodesy and Astrometry (IVS)
• International GNSS Service (IGS)
• International DORIS Service (IDS)

The products derived from data produced by NASA’s Space Geodesy Project systems can be downloaded from the CDDIS. These products include:

• SLR: Laser ranging products consist 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). These products are available from the CDDIS in subdirectories by product type at: https://cddis.nasa.gov/archive/slr/products. More information about these products can be found at:
  • CDDIS: https://cddis.nasa.gov/Data_and_Derived_Products/SLR/SLR_product_holdings.html
  • ILRS: https://ilrs.gsfc.nasa.gov/science/analysisProducts/index.html
• VLBI: The CDDIS archive of VLBI products consists of solutions derived by IVS analysis centers from the analysis of VLBI experiment files. These products include station positions and velocities; positions of quasars (input to the International Celestial Reference Frame, ICRF); EOPs (polar motion and rates, length-of-day); UT1-UTC and long-term stability of nutation); and troposphere parameters. Derived product files are available from the CDDIS in subdirectories by product type at https://cddis.nasa.gov/archive/vlbi/ivsproducts. GSFC VLBI product file names start with gsf. More information about these products can be found at:
  • CDDIS: https://cddis.nasa.gov/Data_and_Derived_Products/VLBI/VLBI_product_holdings.html
  • IVS: https://ivscc.gsfc.nasa.gov/products-data/products.html
• GNSS: Products derived from GNSS data archived in the CDDIS are generated and submitted by the IGS analysis and associate analysis centers. IGS operational products include precise GNSS satellite ephemerides; positions and velocities of stations in the global GNSS network; EOPs (polar motion and rates, length-of-day); and station and satellite clock solutions. Other products derived from the CDDIS GNSS data holdings include troposphere Zenith Path Delay (ZPD) estimates (both dry and wet components) and global ionosphere maps. More information about these products can be found at:
  • CDDIS: https://cddis.nasa.gov/Data_and_Derived_Products/GNSS/GNSS_data_holdings.html
  • IGS: http://www.igs.org/products
• DORIS: Products derived from DORIS measurements consist of solutions provided by IDS analysis centers and include precise satellite ephemerides, station positions and velocities (input to the derivation of the ITRF); time series of station coordinates; EOP (polar motion, length-of-day); and time derivatives of vertical Total Electron Content (TEC). More information about these products can be found at:
  • CDDIS: https://cddis.nasa.gov/Data_and_Derived_Products/DORIS/doris_product_holdings.html
  • IDS: https://ids-doris.org/ids/data-products/tables-of-data-products.html