Soyuz MS-03 undocks, conducts rare two-person landing

by Chris Gebhardt

In what is a rare event in recent history, the Russian Federal Space Agency has returned the Soyuz MS-03 crew capsule from the International Space Station with just two crew members.  The Soyuz undocked from the ISS at 06:47 EDT (10:47 GMT) Friday, 2 June with two of the Station’s five crew members – with landing on the Kazakh steppes following at 10:10:38 EDT (14:10:38 GMT) with Russian cosmonaut Oleg Novitskiy and European Space Agency astronaut Thomas Pesquet.

Detailing undocking, entry, descent, and landing – Soyuz MS-03 comes home:

By the time their mission ends, Oleg Novitskiy and Thomas Pesquet will have spent over 196 days in space since launching to the International Space Station on 17 November 2016.

During their time aboard the orbital outpost, the crew – along with NASA astronaut Peggy Whitson, whom they launched with – welcomed five visiting vehicles to the Station, four cargo resupply missions and one crewed Soyuz vehicle.

Leaving just days before the arrival of SpaceX’s next scheduled resupply run to the Station, the departure of Novitskiy and Pesquet on Soyuz MS-03 will leave the ISS with three crew members for a rather prolonged period, as the next crewed Soyuz (Soyuz MS-05) to the Station will not launch until 27 July.

The MS-05 mission had been slated to launch on 29 May, but a technical issue in January necessitated the shuffling of the Soyuz capsules scheduled to fly the MS-04, MS-05, and MS-06 missions.

The Soyuz for MS-05 had originally been assigned to the MS-06 mission and suddenly found its schedule advanced significantly – with engineers only able to pull the craft’s launch readiness to late-July – thus delaying the MS-05 flight by two months.

With this delay known, Roscosmos and ESA declined to extend the Soyuz MS-03’s mission to match the realigned July launch date of MS-05 and determined that bringing MS-03 and its two person crew home in early June was best.

Preparations for landing of Soyuz MS-03 began with a careful choreography to ensure that the landing takes place in daylight on the steppes of Kazakhstan.

This plan resulted in an 18 May firing of the Zvezda Service Module’s thrusters to adjust the Station’s orbit.

The thruster burn lasted 13 seconds and resulted in a delta-V change to the International Space Station’s speed of 0.2 m/s (0.65 f/s).

The burn correspondingly altered the orbit of the Station, leaving it in a 424 x 401.8 km (263.4 x 249.6 mi) orbit inclined 51.66 degrees with an orbital period of 92.675 minutes.

For today’s undocking, the departure sequence began when the ISS was commanded into its Solar Alpha Rotary Joint (SARJ) park attitude at 02:16 EDT (06:16 GMT).

The SARJs – one on each side of the Station’s long Integrated Truss Structure (ITS) which supports, among other essential items, the ISS’s solar arrays – are giant gears that turn the outboard portions of the ITS to allow the solar arrays to track the sun during the Station’s orbit.

For visiting vehicle arrivals and departures, the SARJs are immobilized to hold the solar arrays in a specific position to protect them from vehicle arrivals and departures and to give those vehicles as clear a path as possible to and from the ISS.

With the SARJs disabled, the ISS has to repositioned to allow for as-optimal-as-possible solar array collection of the sun’s useful rays for energy production.

Following SARJ park attitude adjustment, the crew held a farewell ceremony at 03:00 EDT (07:00 GMT), culminating with Novitskiy and Pesquet entering the Soyuz ahead of hatch closure, which occurred at 03:33 EDT (07:33 GMT).

Following vestibule depressurisation, the “undock” command was transmitted from the Soyuz MS-03’s computers at 06:45:30 EDT (10:45:30 GMT) and began the 90sec process of retracting the screws which anchored the Soyuz to its docking port on the Station’s MRM-1 Nadir port.

Undocking occurred with hook opening and spring-powered push-back for a physical separation of Soyuz MS-03 from the International Space Station at 06:47 EDT (10:47 GMT) at a Mission Elapsed Time (MET) of 196 days 14 hours 26 minutes 47 seconds.

Undocking occurred three minutes ahead of the pre-published timeline.

The push Soyuz received from the springs at undocking imparted a delta-V change of 0.12 m/s (0.39 f/s) and provided all the energy Soyuz needed for the first 10 seconds of free flight away from the Station.

Ten seconds after departure, the Soyuz began active attitude control, followed 15 seconds after undocking by the ISS transitioning to an attitude hold position as the Soyuz continued to back away under just the propulsive energy of its spring release.

After three minutes of non-propulsive free flight, Soyuz performed Separation Burn #1, an 8-second burn of its thrusters to impart a delta-V shift of 0.54 m/s (1.7 f/s).

Two seconds after completing its first burn, Soyuz began an attitude change maneuver to properly align itself for Separation Burn #2, which occurred 4 minutes 20 seconds after undocking.

The second separation burn was a 15-second thruster firing to impart a delta-V change of 1.53 m/s (5 f/s).

Soyuz then coast into an orbital sunset 12 minutes 56 seconds after physical separation from the ISS at 06:59:56 EDT (10:59:56 GMT).

The Station itself then maneuvered into its post undocking attitude 10 minutes after undocking at 06:57 EDT (10:57 GMT).

The two separation burns enabled Soyuz to travel to a range of 2 km (1.2 mi) from the International Space Station just 26 minutes 20 seconds after undocking, increasing that range to 6 km (3.7 mi) by 38 minutes 20 seconds after undocking.

The Station then maneuvered back to its standard orientation and the SARJs were switched back into autotrack mode at 08:27 EDT (12:27 GMT).

Following undocking, the Soyuz MS-03 crew experienced two orbital sunrises, the final of which occurred at 09:11:14 EDT (13:11:14 GMT) – just 6 minutes prior to the deorbit burn.

With all going to plan, Mission Control Center – Moscow (MCC-M) gave the final “go” for Soyuz’s return.

The Soyuz MS-03 began its deorbit burn at 09:17:09 EDT (13:17:09 GMT).

The deorbit burn lasted a full 4 minutes 37 seconds and imparted a delta-V change of 128 m/s (91.8 f/s), slowing the Soyuz enough to be grabbed by Earth’s gravity while keeping the craft on proper alignment for its primary landing site.

Following cut off of the deorbit burn at 09:21:44 EDT (13:21:44 GMT), Soyuz entered a coast phase before the vehicle itself separated into its three distinct modules at 09:44:32 EDT (13:44:32 GMT).

Vehicle separation occurred at an altitude of 140 km (87 mi).

The descent module then performed atmospheric entry at an altitude of 99.7 km (61.9 mi) at 09:47:25 EDT (13:47:25 GMT).

The Soyuz’s descent module entered the plasma stage of reentry, switching on its entry guidance sequence, at an altitude of 80.5 km (50 mi) at 09:48:54 EDT (13:48:54 GMT).

Under the nominal entry sequence, the Soyuz descent module exited the plasma stage of reentry, experiencing its maximum G-load at an altitude of 35.9 km (22.3 mi) at 09:53:37 EDT (13:53:37 GMT).

Soyuz then fell under its own weight until it reached an altitude of 10.7 km (6.6 mi), at which point the command to deploy its parachute was issued by the descent module’s computers.

Parachute deployment occurred at 09:55:38 EDT (13:55:38 GMT), beginning a 15-minute parachute descent sequence to the ground.

Soyuz MS-03 successfully landed on the steppes of Kazakhstan at 10:10:38 EDT (14:10:38 GMT) at coordinates 47°18’ N by 69°35’ E.

With landing, Soyuz MS-03 amassed a total mission duration of 196 days 17 hours 50 minutes 25 seconds – touching down on the ground just 3 hours 23 minutes 38 seconds after undocking.

Once the Soyuz is safely on the ground, recovery forces will quickly arrive at the landing location to assist the two crewmembers with their egress from the vehicle.

Initial medical testing of the crew will take place once they are removed from the Soyuz descent module.

Once those initial tests are complete, Novitskiy and Pesquet will part ways, returning to their respective space agency’s bases for additional medical observations as they readjust to gravity after half a year off planet Earth.

(Images: NASA, ESA, Roscosmos, Google Maps)

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