Precise orbits for the year 2018 and attitude quaternions for the period from January 2014 to January 2019 were produced for the CASSIOPE/e-POP, which was incorporated as the fourth element of the Swarm constellation (Swarm-Echo) in 2018. These data sets are now available on the Swarm dissemination server.

The orbits have an accuracy of approximately 10 cm during continued GAP-A instrument operation and 1 m when data gaps are interpolated. In rare cases, when no data is available either at the beginning or end of a data segment, the extrapolation of the orbit results in much higher errors depending on the length of the extrapolation.

The satellite attitude quaternions are derived from the data of the two star cameras, which were corrected for relative biases. The precision of the attitude is expected to be approximately 30" when both cameras are available and 200" when only one star camera is available. Thus, the new precise orbits and attitude are much more accurate than previously available data sets.

The new orbits and attitude quaternions are available on the Swarm dissemination server, via anonymous FTP or HTTPS, under the following folders:

• /#CASSIOPE_e-POP/Precise_Orbit_Data
• /#CASSIOPE_e-POP/Precise_Attitude_Data

The precise orbits are provided in SP3 file format, whereas the format of the attitude quaternions is explained in a "readme" file located in the same folder as the attitude quaternions files. Both file formats indicate whether data is directly derived from measurements or interpolated. For further information, we refer to Montenbruck et al. (2019) and Technical Report ESA-EOPSM-SWRM-TN-3487.