From 12 December 2018, at 13:34:56 UTC and 18 December 2018, at 12:43:30 UTC, the attitude information of the Star Tracker (STR) instruments on board the Swarm Alpha and Charlie satellites, respectively, are provided at 2 Hz rate, instead of the previous 1 Hz.

This change required an update in the Level 1b processing of the rotation angles from the three Camera Head Unit (CHU) reference frames to Star Tracker Common Reference Frame.
The update was deployed into operations on 6 March 2019.

To benefit from this rotation update, all the Swarm Alpha L1B data from 12/12/2018 to 02/03/2019 and Swarm Charlie L1B data from 18/12/2018 to 02/03/2019 were regenerated and are now available on the Swarm FTP server with increased File Counter.

The effect of this update is a difference of no more than 2 nT in the B_NEC (North-Earth-Center frame) with respect to data available before the update.