Editor’s Note: Progress M-09M/41P undocked nominally today at 13:41 CEST. An automated 15-second separation burn with the vessel’s DPO-K2 thrusters followed at 13:44 CEST, followed by a retrograde phasing burn with the SKD engine at 16:48 CEST. The cargo ship, loaded with trash, is now continuing to phase away from the ISS. It will perform two retrograde burns on 23 April, one on 24 April, one on 25 April and a last one on 26 April – the 67.4 metres/second ‘deorbit’ burn for destructive reentry. A few hours ago, we received an email from ESA’s Charlotte Beskow, Deputy Head of ATV Production Programme, reporting the details of ATV’s crucial role for today’s undocking.

Charlotte writes:

We just performed attitude control for the ISS to prepare for a Russian Vehicle undocking. Normally, we are only supposed to fly the ISS level to the Earth – but for today’s operation, a completely different attitude was requested: The ISS flew upside down and back-to-front!

In the first picture (see animation above) you see ATV. It is at the rear of the ISS (in the middle, lower part of the first picture, with X-shaped solar panels). Then, in the following pictures you see the entire station first skewing, then flipping – all powered by ATV.

After a short time in this position we performed an inverse manoeuvre, to bring the ISS back to a nominal attitude.

We had a computer model up and running that took the actual ISS coordinates and visualised the station’s orientation using a computerised model; I attach the pictures here – pretty impressive!! [We included them as an animation – Ed.]

All the calculations of thruster impulses were done by our Russian colleagues; Russian computers commanded the ATV thrusters as if it were their own. We were basically spectators down here at ATV-CC in Toulouse (at least when we had communications, which was most of the time, despite our funny attitude).