Inside Russian Spacewalk 66: New Solar Experiment and Antenna Inspection on the ISS

Hardware Installed: Solar Radiation Sensor on Zvezda

The centerpiece of the installation work was a new solar radiation-measuring device, which the pair mounted on the exterior of the Zvezda service module . Operating in the harsh environment outside the station's Russian segment, the new instrument is designed to collect data on solar particle activity, helping researchers understand the radiation hazards astronauts face during long-duration missions. This data supports planning for future deep-space exploration, where crews will venture beyond Earth's protective magnetic bubble.

Hardware Retrieved: Biological Exposure Experiments

The cosmonauts also removed two completed science experiments from the exterior of the Poisk and Nauka modules . While Roscosmos has not publicly detailed exactly which biological materials were exposed, such experiments typically involve hardy organisms or biomolecules placed outside to study how they withstand the vacuum, extreme temperature swings, and unfiltered cosmic radiation. Retrieving these samples allows scientists on Earth to analyze damage and survival rates, which feeds into both fundamental astrobiology research and practical spacecraft shielding design.

Progress 94 Antenna Inspection: A Troubleshooting Photo Shoot

Listed as an “if time allows” task, the duo successfully photographed one of the Kurs rendezvous antennas on the Progress 94 (Progress MS-33) cargo spacecraft . The antenna in question had failed to deploy properly following the freighter's launch and arrival in March, raising concerns about the craft's ability to execute future automated dockings . By capturing detailed imagery of the faulted hardware, engineers on the ground gained crucial visual data to diagnose the malfunction and plan potential repairs or workarounds. The task underscored how modern spacewalks often mix scheduled maintenance with real-time problem solving.

Career Milestones for Kud-Sverchkov and Mikaev

For Sergei Mikaev, this outing was a signature career moment—his first time working in the vacuum of space . Experienced commander Sergey Kud-Sverchkov added a second spacewalk to his resume, having previously ventured outside the station during Expedition 64 in November 2020 to prepare for the arrival of a new Russian research module . The successful completion of Russian Spacewalk 66 marked the second extravehicular activity for the Expedition 74 increment and the second spacewalk globally in 2026 .

Context: A Busy Expedition 74

The spacewalk took place amid a packed research schedule aboard the orbiting laboratory. In the weeks leading up to the excursion, the international crew had been unpacking a freshly arrived SpaceX Dragon cargo ship and conducting experiments ranging from cancer and blood research to cartilage repair studies . Kud-Sverchkov and Mikaev themselves spent their days leading up to the spacewalk on an exercise bike with cardiac sensors for a fitness evaluation, then moved on to inspecting Orlan spacesuit components and practicing every step of the procedure .

As is standard for ISS operations, NASA flight engineer Jessica Meir assisted the cosmonauts with suiting up inside the Poisk module's airlock and monitored their progress from inside the station . The successful completion of all primary and secondary tasks by 4:24 p.m. EDT demonstrated both the meticulous preparation by the ground teams and the growing experience of the Russian segment's crew, even as one of them took his very first steps into the void.