April marked Expedition 67’s first full month aboard the International Space Station, with the outpost’s crew receiving visitors in the form of the Axiom-1 mission before Crew Dragon Freedom arrived at the end of the month to begin a crew rotation on the US Orbital Segment.
On the Russian side of the station, work to commission the Nauka module continued with a pair of spacewalks aimed at activating the module’s European Robotic Arm. On top of this, the crew carried out their daily duties, conducting research and carrying out tasks to keep the station operational.
Two SpaceX Crew Dragon missions visited the space station in April, with Endeavour docking at International Docking Adaptor Zenith (IDA-Z) on Pressurized Mating Adaptor 3 (PMA-3), attached to the zenith – or Earth-opposed – side of the Harmony module.
Endeavour was flying the Axiom-1 mission, the first fully-commercial visiting crew research mission to the ISS, with astronauts Michael López-Alegría, Larry Connor, Mark Pathy, and Eytan Stibbe using their time in orbit to carry out research and pave the way for future commercial missions to be flown by Axiom Space.
Endeavour – making its third trip to the space station – was docked for just over two weeks with its planned departure delayed a few days due to weather conditions at its recovery sites. After undocking early on 25 April, Endeavour made a safe and successful return to Earth with her crew, splashing down in the Atlantic Ocean.
Crew Dragon Endeavour seen from the ISS during the Axiom-1 mission (credit: NASA)
The late departure of Endeavour caused knock-on delays to the Crew-4 mission, a US crew rotation mission that finally lifted off on 27 April. Carrying out its first mission, Crew Dragon Freedom docked with the IDA-Z port just under sixteen hours after launch. Aboard were NASA astronauts Kjell Lindgren, Robert Hines, and Jessica Watkins, as well as Samantha Cristoforetti of the European Space Agency (ESA). They will remain aboard the space station until September, replacing the Crew-3 astronauts ahead of their return to Earth at the start of May.
Aside from the two Dragon arrivals and the subsequent departure of Endeavour, the station saw no other visiting vehicle movements in April. On the US side of the station, other than the Axiom and Crew-4 Dragon capsules using IDA-Z, Crew Dragon Endurance spent April docked at the forward port of the Harmony module via PMA-2 and IDA Forward (IDA-F), where it had been since its arrival with the Crew-3 astronauts last November. The Cygnus NG-17 spacecraft, S.S. Piers Sellers has been berthed at the nadir – or Earth-facing – port of the Unity module since February.
Two Progress resupply spacecraft are currently docked to the Russian segment of the station: Progress MS-18 occupies the aft port of the Zvezda module, having arrived last October; Progress MS-19 is docked to the zenith port of the Poisk module, where it has been since February. The Soyuz MS-21 crew vehicle that arrived in March is docked at the nadir port of the Prichal node.
Progress MS-18 was called upon to adjust the ISS’ orbit on 23 April, firing its thrusters for 623 seconds in a predetermined debris avoidance maneuver — a routine precaution to ensure that a tracked piece of orbital debris could not pose any danger to the outpost or its crew. The maneuver increased the station’s velocity by one meter per second and its average altitude by about 1.8 kilometers.
Russian cosmonauts Oleg Artemyev and Denis Matveev made two spacewalks over the course of the month, preparing the European Robotic Arm (ERA), attached to the Nauka module, for service. The first of these took place on 18 April, with the cosmonauts spending six hours and 37 minutes outside the station. The second, ten days later, lasted seven hours and 43 minutes.
Matveev and Artemyev work outside the Nauka module during the 18 April EVA (credit: NASA)
Both spacewalks were made from the Poisk module using Russian Orlan-MKS spacesuits. After making their way to their worksites on the Nauka module with the aid of a Strela crane, the cosmonauts installed an external control panel for the ERA, removed launch covers, and installed handrails. During the second EVA, the cosmonauts finished removing the launch covers and jettisoned them overboard before releasing launch locks from the arm.
The ERA was moved for the first time since launch during this EVA, relocating from its launch position to its initial base station.
As the only humans aboard the ISS, the Expedition 67 astronauts and cosmonauts serve not just as researchers, but also as test subjects, repair technicians, janitors, photographers, and in the myriad of other roles necessary to keep their outpost operational, conduct scientific experiments and continually upgrade its capabilities.
Early in the month, a series of materials science experiments were performed as part of the Universal Intelligent Glass Optics (UNIGLO) experiment. UNIGLO investigates the production of fiber optics by the processing of complex glasses in microgravity with the aid of artificial intelligence. At the start of the month, the crew exchanged the experiment’s fiber optic spool and preform – the rod of raw material that it processes. These were removed the next day, with the experiment moving into its next phase using crystallization probes instead, with several more runs conducted over the next few days.
One of the Astrobee free-flying helper robots was modified with the installation of an RFID tag reader as part of the RFID Recon experiment. RFID tags have been installed on some of the cargo stored aboard the station, with the experiment aimed at seeing if the robot can use these to help the crew locate specific items that they may need.
Astronaut Megan McArthur works with the three Astrobees in October 2021 (credit: NASA/Shane Kimbrough)
There are three Astrobee units aboard the ISS, named Honey, Bumble, and Queen. These robots are cube-shaped with sides of 32 centimeters and use fans to maneuver around the station. They are designed to help the crew with their daily tasks and research programs.
In another experiment Integrated System for Autonomous and Adaptive Caretaking (ISAAC), an Astrobee was used to test techniques for autonomous monitoring and response to faults aboard the ISS.
In the closed system environment of the space station, monitoring the quality of the air the crew breathes is important to protect their health and wellbeing. The Airborne Particulate Monitor (APM) is being tested aboard the ISS to help with this process: the instrument is designed to characterize air quality in the station, detecting and measuring the concentration of different particles in the air.
At the start of the month, the crew performed an inspection of the APM and downloaded data from its memory card to one of the station’s computers for subsequent downlink to controllers on Earth. Later in the month they collected and analyzed air samples using the Analyzing Interferometer for Ambient Air 2 (ANITA-2) instrument, which is designed to detect both known and unknown contaminants in the air. The astronauts were also called upon to improvise a shield from Kapton tape to place around ANITA-2’s switch to protect it from being inadvertently thrown if the instrument is bumped by a crewmember.
The crew tested the AstroRad vest aboard the station (credit: NASA)
The crew carried out several tests with the AstroRad Vest, a protective garment designed to limit astronauts’ exposure to harmful ionizing radiation of the kind that might be caused by unpredictable solar events. The crew is testing the vest aboard the ISS to assess its comfort and its impact on their daily tasks, with some sessions lasting an hour or two, while others saw the astronauts wear the vest overnight. Later in the month some of the Axiom-1 crew also participated in the research.
The Vascular Aging research program is designed to study changes in astronauts’ cardiovascular health that can occur during long-term spaceflight, with effects similar to the aging process. The research included measuring the blood pressure of participants, taking ultrasound scans, measuring blood glucose levels, and collecting data from wearable sensors.
Astronauts also participated in the Nutrition Monitoring for the ISS (NutrISS) study, completing questionnaires and taking measurements with a bioimpedance device to investigate changes in body composition and mass over the course of space missions. Data from this experiment will be used to help design new diets for astronauts which it is hoped will help to reduce the effects of long-term microgravity on their muscle mass and bone density.
Another nutrition-focused experiment, Food Physiology, looked into how the crew’s diet affected their immune system and microorganisms in their digestive systems. This is aimed at studying how improvements in the crew’s diet affect their bodies and whether controlling this can improve their adaptation to being in space.
The crew shares a meal as part of the Food Physiology experiment (credit: ESA/Matthias Maurer)
The crew participated in the European Space Agency’s Myotones research, which studied the crew’s muscle tone and stiffness to help design better treatments for muscle loss in astronauts returning to Earth.
Routine maintenance on the station’s hygiene systems was carried out throughout the month, with the crew performing a deep clean of the Exploration ECLSS toilet, installing new tethers to help the crew position themselves in the stall, and removing and replacing key parts of the Waste and Hygiene Compartment (WHC). The pretreated urine sample adapter, brine processor assembly bladder, pre-treat tank, urine receptacle, and insert filter were all replaced.
Following its replacement, the new urine receptacle was found to be unresponsive to commands and, after an attempt at troubleshooting, had to be replaced again. This was successful, however, the work created dents in the receptacle’s valve housing which the crew covered with tape to prevent flakes of paint from detaching. Further problems with the receptacle’s valve were fixed by the crew tapping it.
Maintenance was also performed on the Advanced Resistive Exercise Device (ARED), including quarterly inspections and a replacement of the bench’s four mounting cleats – a task that is completed every three years. ARED’s left upper stop cable was replaced after it broke later in the month.
Having carried out maintenance on the Oxygen Generation Assembly in March, the crew flushed the system, took a water sample from its recirculation loop, and replaced a hydrogen sensor. With these tasks completed the system was re-activated, while the water sample was prepared to be sent back to Earth for analysis. The crew also carried out a repressurization of the nitrogen and oxygen tanks in the Quest airlock using Nitrogen/Oxygen Recharge System (NORS) transfer tanks.
Astronauts Kjell Lindgren, Kayla Barron, Samantha Cristoforetti (L-R), and Jessica Watkins (top) familiarise themselves with ISS systems (credit: NASA)
As May begins, the Expedition 67 crew is gearing up for another busy month. The departure of Endurance with the Crew-3 astronauts frees up the IDA-F docking port for Boeing’s OFT-2 mission, a reflight of Starliner’s uncrewed test flight after 2019’s OFT-1 mission failed to reach the space station. Starliner is expected to remain at the station for a few days before departing for its return to Earth. The Cygnus spacecraft, S.S. Piers Sellers, is also expected to depart.
Cosmonauts Artemyev and Matveev will make another spacewalk towards the middle of the month as they step outside to continue work on the European Robotic Arm and to deploy five small satellites.
These activities will be in addition to the crew’s regular duties of performing research aboard the station, fulfilling public relations commitments, and carrying out the repairs and maintenance tasks required to keep the outpost operational.
(Lead image: The ISS seen from Crew Dragon Endeavour during a flyaround late last year — credit: NASA)