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.

Related data and information links
- International GNSS Service (IGS)
- IGS Tracking Stations
- IGS Analysis Centers
- IGS Data Centers
- IGS Analysis Center Coordinator (ACC) web sites
- IGS Real-Time Service (RTS)
- IGS Multi-GNSS Experiment (MGEX), including satellite information
- GNSS system status information
- IGS data and product formats
- RINEX Version 2.11
- RINEX Version 3.03
- NOAA's Continuously Operating Reference Stations (CORS)
- UNAVCO
- GPS Seamless Archive Center (GSAC)
- Russian GLONASS Home Page
- International GLONASS Experiment (IGEX-98)
- Interactive GPS Calendar
- Earth orientation animations
