On June 9, 2015, at 15:27 GMT, while the ISS was in the hands of the American mission control in Houston, the station experienced sudden roll movement, confusing the onboard attitude-control gyroscopes, according to NASA. As it turned out, the torque was caused by small attitude control and rendezvous thrusters, DPOs, onboard the Soyuz TMA-15M spacecraft. The thrusters fired unexpectedly for around 38 seconds, NASA said. They were activated after routine checks of the Kurs rendezvous system onboard the Soyuz TMA-15M spacecraft in preparation for its undocking and landing a day later. The mission control in Korolev immediately commanded the spacecraft to stop the firing and the flight control was then safely transferred back to Houston.

According to Roskosmos, the inadvertent firing took place at 18:32 Moscow Time (15:32 GMT) during the planned test of the Kurs rendezvous system. The particular hardware was located onboard the Zarya Control Module, Kurs-P, and the Soyuz spacecraft, Kurs-A. The "passive" part of the Kurs on the Zarya is responsible for the docking operations on the Earth-facing post of the MIM1 Rassvet module -- the current location of the Soyuz TMA-15.

According to the official TASS news agency, the testing sequence for the Kurs rendezvous system, which was uploaded from the ground, could contain errors leading to the firing of several thrusters. At the time of the test, the crew was also preparing the Soyuz for its departure and one of its members could accidentally flip switches activating thrusters, industry sources said.

Following the loss of the Progress M-27M spacecraft on April 28, 2015, the departure of the Soyuz TMA-15M spacecraft from the International Space Station, ISS, had to be postponed from May 12 until June 11, 2015.

According to the new schedule, Terry Virts, Anton Shkaplerov and Samantha Cristoforetti were to board their spacecraft from 09:55 Moscow Time to 10:15 Moscow Time (2:55 a.m. - 3:15 a.m. EDT) on June 11, after 199 days in space. The hatches were closed between the ISS and the Soyuz at 10:04 Moscow Time (3:04 a.m. EDT) on June 11, 2015.

The mission control in Korolev sent an undocking command to the spacecraft at 13:18:30 Moscow Time (6:18 a.m. EDT). After opening of hooks on two sides of the docking port and the activation of spring pushers, the Soyuz separated from the Earth-facing docking port of the MIM1 Rassvet module on the Russian segment of the ISS at 13:20:00 Moscow Time (6:20 a.m. EDT) as two spacecraft were flying over Southern Mongolia. Three minutes later, thrusters on the Soyuz fired for eight seconds to deliver around 0.5 meters per second in velocity to increase its distance from the ISS. Another 30-second firing adding 1.5 meters in velocity further increased the distance between two spacecraft.

A four-minute 40 second engine firing to push the Soyuz off its orbit was initiated at 15:51 Moscow Time (8:51 a.m. EDT), as the spacecraft was around 12 kilometers from the station orbiting the Earth over the South Atlantic of the coast of Argentina.

The Soyuz then split into the descent module with the crew heading for landing and into the habitation module, BO, and the instrument compartment, PAO, both of which burned up on reentry.

The sunrise took place at the site at 02:25 Moscow Time. Rescue services, equipped with a dozen of Mi-8 helicopters and other aircraft had until 18:18 Moscow Time before a local sunset. Eight helicopters were deployed near the primary landing site and four others flew further west toward a touchdown point expected in the unlikely event of a ballistic reentry of the Soyuz' descent module. Good weather was forecasted for the landing region.