Following its orbit corrections, Soyuz TMA-20M began an autonomous rendezvous with the ISS around 04:03:38 Moscow Time on March 19 (9:03 p.m. EDT).

The final maneuvers, including flyaround, a short station-keeping period and berthing, were scheduled to be initiated at 05:47:09 Moscow Time on March 19 (10:47 p.m. EDT on March 18) in fully automated mode.

The docking of Soyuz TMA-20M with the ISS was scheduled on the day of the launch at 06:11:47 Moscow Time (11:11 p.m. EDT on March 18). The actual first contact between the two spacecraft took place at 11:09:55 p.m. EDT on March 18.

The spacecraft docked at the zenith port of the MIM2 Poisk module on the Russian segment of the outpost.

During their six-month mission, Williams served as Commander of Expedition 48, with Ovchinin and Skripochka serving as Flight Engineers.

The Expedition 48 crew members contributed to hundreds of experiments in biology, biotechnology, physical science and Earth science during 172 days in space for the crew.

of Williams mission included the installation, inflation and ingress into the Bigelow Expandable Activity Module (BEAM).

BEAM – launched in the trunk of the CRS-8 SpaceX Dragon – is a technology demonstrator, with the challenges providing engineers with lessons learned ahead of moving on to larger expandable modules.

The larger modules are likely to play a huge role in the exploration of deep space.

The BEAM module is hoped to be a stepping stone designed to gain useful in-flight experience of how expendable technology works with human spaceflight activities before the notional launch of the two B330 modules at the beginning of the next decade.

Williams also participated in two spacewalks during his time on Station, the first – EVA-36 – involving the installation of the long-awaited International Docking Adapter (IDA).

The first of two IDAs, this piece of hardware is designed to convert the US Segment’s old Shuttle-era docking ports to a new docking system, thus allowing them to accept the upcoming commercial crew vehicles which will all use the updated docking system design.

Williams only recently completed a second spacewalk, joining forces once again with Kate Rubins, as the duo completed EVA-The spacewalkers successfully stowed a now unused spare radiator and also installed the first two hardware elements of a new system of external HD television camera.

Williams’ conclusion to his mission also saw him eclipse the record set by Scott Kelly for the most cumulative time spent by a NASA astronaut in space.

Williams returned to Earth having accrued 534 days in space on his four missions dating back to 2000, the most days by any US astronaut in history.

Preparations for departure began several days ago. This included a checkout on the crew’s ride home.

“In preparation for departure, the Crew successfully completed a thruster test on the vehicle. This was the first Soyuz thruster test conducted in Control Moment Gyroscope (CMG) Momentum Management (MM) control,” noted L2 ISS Status.

“By utilizing CMG MM for the thruster test, there is a potential to save approximately 5-20kg of propulsion during each thruster test.”

The crew then parted ways with their colleagues during Tuesday, with farewell speeches and hatch closures between the Station and the Soyuz.

With the crew completing the translation from the Orbital Module (BO) and Descent Module (SA) to strap themselves into their Kazbek couches inside the SA, Soyuz TMA-20M undocked from the ISS at 21:51 UTC.

Expedition 49 began aboard the station under the command of Anatoly Ivanishin of Roscosmos as the Soyuz departed.

Along with his crewmates Kate Rubins of NASA and Takuya Onishi of the Japan Aerospace Exploration Agency, the three-person crew will operate the station for more than two weeks until the arrival of three new crew members.