Here’s a quick run down on what’s happening today and in the past couple of days as the astros have been preparing for undocking.
Prior to hatch closure the crew remove safety equipment (fire extinguisher and breathing apparatus), an inter-module air hose, and various hand grips and restraints from inside the ATV. They turn on a valve that stabilises ATV pressure after hatch closure, and turn off the ATV fan and smoke detectors.
One day before leaving, the ATV hatch is closed and 16 quick release clamps are removed from around the periphery of the inter-hatch area between the ATV and the ISS. These equally spaced clamps further strengthened the connection between the ATV and the ISS during the docked phase. The crew now take a cap off an ATV depressurisation valve, carry out a final inspection of the interhatch area and close the ISS hatch. A pressure sensor is hereafter installed on the ISS hatch, the area between the hatches is depressurised (controlled by the ATV Control Centre), and a leak check is performed by the ISS crew.
Note this description came from the ATV1 info kit, and today’s activities may vary in detail – but overall, this is what’s happening.