The satellite executed autonomously the mission timeline that had been uplinked during the DTCP. The observational data was stored on board, and downlinked to the New Norcia Ground Station (which was backed-up by the Cebreros Ground Station) during the following DTCP. During this period, which lasted approximately 3 hours, the status of the satellite was monitored and operational or emergency procedures applied, when necessary. In addition, the mission timeline with the commands to be executed during the next OD was uplinked. This though was a rolling process. In the case that a DTCP communications linkage with the ground station were missed, the satellite must always have had two operational days of observations stored in the onboard solid-state memory. This meant that the commands to be executed were always added to the end of the onboard file so that, in the case of a communications failure, there would always be sufficient commands on board to last until the end of the DTCP of the following OD, allowing time for recovery and the uplink of further observations.

It took several weeks to complete the planning of an OD, from the compilation of all the inputs needed, to the building of the mission timeline by the MOC. Therefore if there are special scheduling requests they had to be sent, via Helpdesk, two months in advance in order to be able to apply them at the due time. Only in special circumstances, normally if there was a risk of a significant loss of observing time, would changes be authorised on a shorter timescale.

The downlinked satellite telemetry was transferred from the ground station to the MOC, where it was consolidated and made available to the HSC. The HSC retrieved the consolidated telemetry and auxiliary data from the MOC automatically, and ingested them in the HSC database, propagating the data to the Instrument Control Centres for each of the three instruments. After the end of helium, the database of telemetry was checked carefully and any small gaps in the housekeeping telemetry that remained after consolidation, were filled from the MOC master copy.