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

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About the CDDIS DORIS data and products archive

DORIS is a dual-frequency Doppler system consisting of a receiver flying aboard a satellite and a globally distributed network of ground beacons. The DORIS receiver on-board the orbiting satellite tracks the dual-frequency radio signals transmitted by the network of ground beacons and generates the DORIS data. A measurement is made of either the Doppler shift or absolute phase as the satellite’s orbit moves over the ground-based beacon.

DORIS data records contain a time-tagged range-rate measurement with associated ancillary information. The data records also contain information about any corrections that may have been applied during the processing phase, such as for the ionosphere, troposphere, and satellite center of mass, among others. Furthermore, meteorological measurements (e.g., temperature, relative humidity, ground pressure) recorded by instruments co-located with the ground-based beacons are included with the DORIS data and can be used to determine the tropospheric correction.

The CDDIS serves as a global data center for the International DORIS Service (IDS). DORIS data in RINEX format are submitted to the CDDIS daily with a one-day delay. DORIS data in the original format are also supplied to the data center in multi-day files, corresponding to the mission’s data processing arc, and are forwarded approximately 20 days after the end of the last observation day contained in the file.

DORIS installation at GGAO/GSFC
DORIS is based on an uplink device. The receivers are on board the satellite while the transmitters are on the ground. This creates a centralized system in which the complete set of observations is downloaded by the satellite to the ground center, from where they are distributed after editing and processing.