Here’s the rough sequence of events for today’s departure from the ISS. The process is already underway, ISS Hooks Opening took place around 05:10 CET.

  • ISS Hooks Opening The ISS’s mechanical hooks – holding ATV-4 in place – open. Once that happens, only ATV’s own hooks are holding the vessel rigidly attached to the Russian Service Module.
  • WAKE_UP: ATV avionics are switched on – Albert Einstein comes to life!
  • DEMERGING Separation of the data & power links from the Russian SM to ATV-4  – Disconnection of the ISS/ATV communication bus happens about 10 min before mechanical separation.
ATV undocking

ATV undocking


  • ISS Free Drift – Station goes into ‘free drift’ mode  – its attitude and orbit control system will stop making corrections to the Station’s attitude for the remaining duration of undocking.
  • GO for undocking  – ATV-CC/MCC-M
  • ATV-CC sends ATV ‘Hooks opening’ command
  • ATV Separation – first distancing impulse is provided by spring pushers on docking rings(see image above)
  • Departure Manoeuvre – Thruster burn executed about 1 minute after separation
  • End of free drift – ISS returns to normal attitude control
  • ATV leaves approach ellipsoid – ATV pulls back and departs from the safety zone around the ISS to commence free flight orbiting