Delta-DOR (Delta Differential One-Way Ranging) is a Very Long Baseline Interferometry (VLBI) technique that can be used in conjunction with Doppler and ranging data to improve spacecraft navigation by more efficiently determining spacecraft angular position in the plane of sky. It involves the use of multiple ground stations, possibly belonging to different agencies, for simultaneous acquisition of either spacecraft or quasar signals (see reference [D2]).

This Delta-DOR Raw Data Exchange Format (RDEF) Recommended Standard specifies a standard format for use in exchanging Delta-DOR raw data among space agencies. Delta-DOR raw data exchange is required every time the data correlation involves at least one participating station not belonging to the agency responsible for the correlation. ISO 20208:2015 includes specifications on the parameter fields that the data format has been designed to meet. For exchanges where these specifications do not capture the needs of the participating agencies another mechanism may be selected.