Data format and observational modes for the RadioAstron interferometer

To transmit radio-astronomy and auxiliary data from a space radio telescope to a ground tracking station (and then to a correlator) via radio link it is necessary to use a special data format and coding and decoding procedures. Here, the format developed and successfully implemented in the RadioAstron ground-space radio interferometer is considered in detail. The goal of the paper is to present the characteristics necessary for astronomers, observers, designers of tracking stations, and management and planning workgroups, as well as for testing for compatibility of the space radio telescope and tracking stations.