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Cosmonauts conduct VKD-61 spacewalk

Two cosmonauts from the Soyuz MS-24 crew vehicle docked at the ISS performed a spacewalk on the exterior of the Nauka module on Oct. 25, 2023. During the isolation and inspection work around the coolant leak on the Nauka's RTOd add-on radiator, the spacewalkers encountered a major spill of cooling fluid with a potential to contaminate their suits and hardware on the station. The work to install a remote-sensing radar on Nauka was not completed due to failure of the instruments panels to fully deploy, while a cubesat launched during VKD-61 failed to deploy its solar sail.


Cosmonauts install a radar instrument on the Nauka module during the VKD-61 spacewalk.

VKD-61 spacewalk at a glance:

Spacewalker 1 Oleg Kononenko, Orlan-MKS suit No. 5 with red stripes
Spacewalker 2 Nikolai Chub, Orlan-MKS suit No. 4 with blue stripes
Duration 7 hours 41 minutes 30 seconds (actual); 6 hours 52 minutes (planned)
Planned hatch opening 2023 Oct. 25, 20:49:03 Moscow Time (actual); 20:55 Moscow Time (planned)
Planned hatch closure 2023 Oct. 26, 04:30:33 Moscow Time (actual); 03:47 Moscow Time (planned)
Airlock MIM2 Poisk
ISS expedition 70

VKD-61 tasks

Cosmonauts Oleg Kononenko and Nikolai Chub, members of Expedition 70 aboard the ISS, are expected to exit the Poisk module, MIM2, used as an airlock, at 20:55 Moscow Time (1:55 p.m. EDT).

Their first task, to be performed on the exterior of the Nauka module, was added to the VKD-61 program only a couple of weeks before the scheduled spacewalk, after the module's external radiator, RTOd, (INSIDER CONTENT) had suffered a coolant leak on Oct. 9, 2023.

To solve the problem, the cosmonaut will have disconnect the NGK1 and NGK2 hydraulic cooling manifolds of the RTOd radiator from two loops of the Thermal Control System (INSIDER CONTENT) of the Nauka module. Only one loop had been functioning after the Oct. 9 leak and after closure of the valves to RTOd, it was expected to continue operating through body-mounted radiators of the Nauka module.)

The cosmonauts will also inspect and photograph the leak area on the radiator. The operations would pave the way to the eventual repair and restart of the cooling through the RTOd.

The RTOd radiator was installed on the Nauka module during the VKD-56 spacewalk (INSIDER CONTENT) on April 19, 2023, and deployed during the VKD-58 spacewalk (INSIDER CONTENT) on May 13, 2023.

Next, the cosmonauts will perform the original primary task of the VKD-61 spacewalk, installing and deploying the Rakurs synthetic remote-sensing radar for the Napor-miniRSA experiment on the exterior of the Russian Segment. The instrument will be mounted on a special adapter of the UFP2 passive standard attachment point of the Nauka module and will become the module's first science payload (INSIDER CONTENT). According to its developer, RKK Energia, the radar will be used for environmental monitoring. It was delivered to the ISS with the Progress MS-22 cargo ship in February 2023.

The cosmonauts will also release the 1.8-kilogram nano-satellite, called Parus-MGTU, developed at Bauman Moscow State Technical University. The spacecraft has the shape of a cube with 10-centimeter sides and is designed to test a deployment mechanism for an experimental solar sail.

(MGTU is the Russian abbreviation of Moscow State Technical University. The college, known to the Russians by its Soviet-era name Bauman school is the key institution providing cadre for the rocket industry.)

If times allows, the cosmonauts will also move to the Zvezda Service Module, SM, and remove two fixating plates from the two sides of the module's main large-diameter section. The plates are used to hold cables in docked position.

The VKD-61 spacewalk is scheduled to continue until around 04:00 Moscow Time on Oct. 26, 2023, (9 p.m. EDT on October 25).

After hatch closure, the ventilation in the Poisk module is expected to run for about an hour as an extra measure aimed to prevent contamination of the station's interior with traces of toxic coolant.

According to NASA, it would be the 268th spacewalk aboard the ISS, while Kononenko would be performing his sixth sortie outside the station and Chub would be venturing outside for the first time. According to Roskosmos, VKD-61 will be the 61st planned spacewalk from the Russian Segment of the ISS, but the 71st sortie overall, counting improvised spacewalks added into the various ISS missions on as-needed basis.

According to the Russian mission control, the VKD-61 spacewalk had the following sequence tasks:

  • The disconnect of the RTOd from NGK1 and NGK2 external loops;
  • The inspection of the RTOd depressurization (area);
  • Installation of the payload adapter;
  • Installation of the MiniRSA experiment unit;
  • Launch of Parus-MGTU satellite from MLM;
  • Removal of fixation plates on URM-D on Plane I and Plane IV of the service module with subsequent discarding and installation of new plates in their place (of time allows).

At the same time, mission control posted the following timeline for the VKD-61 spacewalk from October 25 to October 26, 2023:

  • 18:05 - 18:50 Moscow Time: Equipment setup, (internal) hatch closing between MIM2 and ISS;
  • 18:50 - 20:49 Moscow Time: Suiting up, airlock depressurization;
  • 20:49 - 20:55 Moscow Time: Egress hatch opening;
  • 20:55 - 03:50 Moscow Time: VKD-61 spacewalk operations;
  • 03:47 - 03:50 Moscow Time: Closure of the ingress hatch;
  • 03:50 - 04:50 Moscow Time: Airlock re-pressurization.

Cosmonauts perform VKD-61 spacewalk


Cosmonauts prepare for a transfer from Poisk to Nauka around an hour into the VKD-61 spacewalk.

After completing airlock operations a few minutes ahead of schedule, Oleg Kononenko and Nikolai Chub opened hatch of the Poisk module at 20:49 Moscow Time (1:49 p.m. EDT) on Oct. 25, 2023, shortly after the station entered an orbital sunset. After a bit of struggle with the hatch, the cosmonaut installed a protective ring on its periphery and Chub was instructed to initiate egress from Poisk, which he reported completing at 20:54 Moscow Time, as the station was over the Indian Ocean out of TV coverage.

Kononenko then transferred Chub bundles of equipment, first the Parus satellite package, then a crew lock bundle, followed by the adapter, and finally the MiniRSA radar assembly. Chub secured the bundles on the gap spanner outside Poisk. Kononenko followed Chub outside at around 21:10 Moscow Time and the cosmonauts then prepared to move to the Strela boom leading from Poisk to Nauka.

First views from the cosmonauts' helmet cameras finally appeared in mission control around 29 minutes into the spacewalk at around 21:18 Moscow Time. After some struggle with equipment, the cosmonauts were finally ready to begin the transfer from Poisk to Nauka along the Strela more than an hour into the spacewalk. They began the move at around 22:00 Moscow Time and reached Nauka a few minutes later.

The cosmonauts opened the flap over the valves of the coolant refueler on Nauka ar around 22:00 Moscow Time. Mission control than instructed Chub to move the 1KL and 2KL bypass valves counterclockwise 90 degrees in open position. Mission control then instructed Chub to close the insulation flap over the valves. Next, Kononenko and Chub instructed to close four valves on the USA interface between the RTOd radiator (INSIDER CONTENT) and the rest of the KSOTR cooling system (INSIDER CONTENT).

Cosmonauts began working on manual valves at around 22:38 Moscow Time, using wing nuts on the valves and rotating them counterclockwise, No. 6, 7, 8, 9. The rotation of manual valves was made in small 90-degree moves.

Cosmonauts took a short break around 22:45 Moscow Time, as the station went into a short handover of communications. At the time, the cosmonauts were around 15 minutes ahead of schedule.

Mission control warned cosmonauts that some coolant could come out from the system after around 25 rotations of each valves. At the 34th rotation all four valves came into

Kononenko then rotated the Kr2 valve into opened position and took its photo at around 22:50 Moscow Time. That completed the isolation of the KSOTR system from the RTOd radiator.

Switching to the inspection, Chub reported some dark areas near the interface as the station emerged from darkness at around 22:56 Moscow Time. No traces of coolant were found on the interface between RTOd and Nauka, but Chub reported seeing some signs of the leak on the connecting line area between the radiator panels just before 23:00 Moscow Time.

Next, cosmonauts were instructed to close the insulation flaps over the coolant fluid connectors at around 23:03 Moscow Time, around 2 hours 15 minutes into the spacewalk.


A couple of bubbles of coolant escaping from a suspected leak area between RTOd radiator panels, as seen by an ISS camera around 23:38 Moscow Time during VKD-61 spacewalk on Oct. 25, 2023.

At around 23:10 cosmonauts reported seeing a considerable amount of coolant forming blobs and bubbles near the bend of a line connecting radiator panels. At least one blob was estimated to reach the size of around 20 centimeters before detaching from the connecting pipe.

The fluid was escaping into space and some came in contact with spacesuits and with an retractable tether used by one of the spacewalkers.

One of the cosmonauts reported a coolant-contaminated tether hitting his visor. "Towel would not be enough here (to clean the leak)," one of the cosmonauts said. Mission control then instructed the spacewalkers to move away from the site. It was decided to remove the contaminated tether and pack it into the bag for subsequent discarding into space. (According to another source, the tether was fixed in place on the exterior of Nauka.)

After talking some additional imagery of the coolant leak area, spacewalkers returned toward Pirs at 2 hours and 48 minutes into the VKD-61 spacewalk (at around 23:37 Moscow Time).

Still ahead of the timeline nearly three hours into the VKD-61, the cosmonauts picked up folded radar instrument stored outside Poisk. One of the locks turned out to be undone, causing the panels to flap on the way to the installation site, but the cosmonauts were able to fix it around 23:50 Moscow Time, or three hours into the spacewalk, as the station entered the nighttime at 23:53 Moscow Time. The also picked an adapter for the installation of the radar and the Parus satellite launch container, however, before the translation to Nauka, mission control advised spacewalkers to take a break around midnight Moscow Time. The cosmonauts transferred to Nauka at around 00:10 Moscow Time.

They approached the installation site at around 00:30 Moscow Time, as the sun again appeared above the horizon. Soon afterwards, mission control insisted on a break and asked cosmonauts remain motionless.


They turned to the installation of the adapter at around 00:40 Moscow Time, removing soft cover from its docking interface and aligning it against the UFP docking mechanism. After docking the adapter, they had to make around 60 turns of a special crank to secure the adapter in place.

Soon after four-hour mark in the spacewalk, at around 00:55 Moscow Time, mission control confirmed that an adapter for the radar instrument had been successfully installed into its location. The spacewalkers then disconnected cables No. 2, 3, 4 and 6 on the near-by electric connector panel for the subsequent wiring of the instrument. All cables were temporarily capped. Electric connections of the instrument had been completed soon after 01:27 Moscow Time, as the station entered another orbital sunset.

The spacewalkers removed the crank tool, revealing the docking interface on the radar instrument adapter at around 01:42 Moscow Time.

At around 01:52 Moscow Time, mission control instructed the spacewalkers to prepare for the deployment of the radar instrument and a couple of minutes later, specialists on the ground confirmed that all electrical connections between the station and the instrument had worked as planned. The temperature of the instrument was also within specifications.

Cosmonauts then were instructed to move to Plane III for the installation of the Parus cubesat launching container on one of the railings of the Nauka module, while engineers on the ground were preparing the deployment of the radar antenna.

The container with Parus was in position around 02:10 Moscow Time or 4 hours 2o minutes into the spacewalk. Kononenko played a role of a launch operator, but first he had to wait for camera setup to document the release of the satellite.

Kononenko pulled out the safety pin on the container at around 02:22 Moscow Time and, within seconds, the cover of the container of opened and spring-loaded mechanism was activated.


Parus-MGTU satellite (top left) floats away from the ISS at around 02:25 Moscow Time on Oct. 26, 2023, as Nikolai Chub documents the release with a Go Pro camera during the VKD-61 spacewalk.

However, the satellite stuck in the container for a few moments before finally floating out at very slow speed. Simultaneously, engineers on the ground were commanding the radar antenna to deploy. They confirmed the opening of the first panel at around 02:28 Moscow Time.

At the same time, mission control and cosmonauts tried to see the deployment of the solar sail mechanism on the Parus satellite, scheduled five minutes after the but tumbling cube showed no signs of extending anything is it was slowly disappearing from the view.

In the meantime, the second panel of the radar was confirmed deployed at 02:36 Moscow Time and the third panel was reported opened around two minutes later, followed by the fourth panel at around 02:40 Moscow Time. Cosmonauts were then instructed to begin transfer back to Strela, which they reached at around 02:45 Moscow Time. Moments later, mission control informed cosmonauts that one panel of the radar system only partially deployed, so the spacewalkers would have to go back to the outer end of Nauka to manually put them into their final deployed position. After consulting with managers about necessary tools, the spacewalkers headed back to Nauka and reached the radar area at around 03:14 Moscow Time. Despite night time conditions, the spacewalkers confirmed that one panel have not reached 180 degrees position relative to a neighboring panel.

The cosmonauts attempted to push the panel in place at around 03:20 Moscow Time, it moved but failed to lock and bounced back, after the first attempt. Mission control asked the spacewalkers to bring a camera closer to one of the locks. The second attempt was made at 03:25 Moscow Time and, this time, one of the latches worked. However, the second latch bounced back and so did the third one.

At 03:30 Moscow Time, mission control told cosmonauts that they have one more attempt to lock the panels and if it failed, the spacewalkers would have return to the airlock. The cosmonauts struggled with the mechanisms for a few more minutes but without success. The cosmonauts confirmed that they were returning to the handrails at 03:38 Moscow Time.


A partially deployed radar as seen during the VKD-61 spacewalk.

The station emerged into daylight, as the spacewalkers were transferring toward Poisk, while ground controllers were beginning the process of planning further course of action on the radar instrument. They reached Strela, extended to Nauka at around 03:50 Moscow Time and returned to the Poisk module at around 04:00 Moscow Time. Before entering the module, the spacewalkers did usual inspection of each other's suits for contamination and conducted inventory of their tools. They ejected a pair of towels used to wipe their suits within a minute around 04:10 Moscow Time.

Kononenko was instructed to ingress Poisk at 04:13 Moscow Time, while Chub remained outside for a few minutes to hand Kononenko the equipment. Chub was cleared to re-enter Poisk at 04:18 Moscow Time but only made it inside at 04:27 Moscow Time.

The hatch of the Poisk module was closed at 04:30:40 Moscow Time, officially concluding the VKD-61 spacewalk after 7 hours and 41 minutes. According to NASA, Kononenko, who made five previous spacewalks, logged 39 hours and 54 minutes outside the station during his career. The total spacewalking time for the ISS project at the end of VKD-61 reached 71 days o hours 7 minutes in 268 spacewalks. It was also the 11th spacewalk aboard the ISS in 2023 and the first for Expedition 70.


To be continued


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This page is maintained by Anatoly Zak; Last update: November 1, 2023

Page editor: Alain Chabot; Last update: October 25, 2023

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Early depiction of the radar imager for the Nauka module. Click to enlarge. Credit: Roskosmos


An isolated view of the Napor-miniRSA radar instrument in deployed position. Credit: Roskosmos


Planned locations of the RTOd coolant line closure and a coolant leak inspection during VKD-61. Click to enlarge. Credit: Roskosmos


Planned locations of the Rakurs radar installation and the launch of the Parus-MGTU satellite during VKD-61. Click to enlarge. Credit: Roskosmos


The location of plates removal on the Service Module during VKD-61. Click to enlarge. Credit: Roskosmos


Click to enlarge. Credit: NASA


Cosmonauts work on extracting folded radar instrument from the Poisk module at around 21:18 Moscow Time on Oct. 25, 2023, after the start of the VKD-61. Click to enlarge. Credit: NASA


A view at the radar adapter and its installation tool during the extraction of the hardware from the Poisk module at around 21:30 Moscow Time on Oct. 25, 2023, after the start of the VKD-61. Click to enlarge. Credit: NASA


A full view of the radar (left) and its adapter with an installation mechanism (right) during preparation outside of the Poisk module. Click to enlarge. Credit: NASA


A view of the 1KL and 2KL manual valves on the Nauka's coolant refueler at around 22:20 p.m. EDT on Oct. 25, 2023, during VKD-61 spacewalk. Click to enlarge. Credit: NASA


Spacewalker documents condition of the RTOd radiator at around 22:58 Moscow Time on Oct. 25, 2023, during the VKD-61 spacewalk. Click to enlarge. Credit: NASA


Kononenko removes installation tool from an adapter holding the radar instrument around 00:42 Moscow Time on Oct. 26, 2023. Click to enlarge. Credit: NASA


Cosmonauts install radar instrument during VKD-61. Click to enlarge. Credit: NASA


Click to enlarge. Credit: NASA


A view of the Parus launch container via Oleg Kononenko's helmet camera before (top) and after opening of the release door. Click to enlarge. Credit: NASA




Parus-MGTU satellite floats away from ISS without deploying its solar sail. Credit: NASA


Nikolai Chub inspects a failed latch on the radar antenna, which failed to fully deploy. Click to enlarge. Credit: Roskosmos