HOUSTON—The surprise November 2021 Russian anti-satellite test (ASAT) has nearly doubled the risk of a penetrating collision between orbital debris and the International Space Station (ISS), NASA ISS Director Robyn Gatens says.
Gatens spoke to the NASA Advisory Council’s Human Exploration and Operations Committee during a Jan. 18 session.
Prior to the Nov. 15 ASAT, the debris penetration risk to the ISS was assessed at one in every 50,000 orbits of the Earth. Since then, the risk has grown to between one in every 33,000 and one in every 25,000 orbits, she told the 10-member committee. Continuously staffed by multinational astronaut and cosmonaut crews, the seven-person orbital lab circles the Earth about 6,000 times each year.
“We have been looking at what the lasting effect of this event is because this debris will be in orbit for some time—for years,” Gatens said during the opening day of a two-day virtual session. “So what is the lasting effect to the environment the space station is flying in? The analysis has showed that it really has increased.”
In the ASAT’s aftermath, the population of orbital debris large enough to be tracked from Earth increased by an estimated 1,500 fragments and many more that are smaller.
In response to the ASAT test, the station’s U.S., European and Russian crewmembers were forced to temporarily take refuge in the SpaceX Crew Dragon and Soyuz crew capsules. The capsules remained docked to the station’s U.S. and Russian segments after transporting the astronauts and cosmonauts to their home in space.
Nonetheless, Gatens expressed confidence that NASA can continue to work with U.S. Space Command in tracking future impact threats to the ISS and providing the warnings needed for ISS avoidance maneuvers.
“We are able to do maneuvers if needed,” Gatens told the 10-member panel, some of whom are former astronauts or once managed NASA human spaceflight programs. “So we know how to operate in this environment of increasing debris and we have procedures for doing it.”
The ASAT, which triggered global alarm, is one of three concerns confronting the ISS at a time NASA is hoping to extend operations from 2024 to 2030. The agency wants to manage an orderly transition of its low Earth orbit human operations to commercially operated stations between 2028 and the end of the decade.
At the same time, NASA is relying on the ISS to enable the development and test of life support technologies. They range from the recycling of urine for drinking water to removing carbon dioxide from the breathing air to make possible future human deep-space exploration, first at the Moon and then Mars. At the same time, the ISS is nurturing scientific research and new technologies with economic and human health payoffs. They include 3D manufacturing, the production of higher-quality fiber optics and the culturing of retinas and other human tissues for transplant.
Other ISS concerns briefed to the committee included the unanticipated thruster firings of Russia’s Nauka Multipurpose Laboratory Module just after the large structure rendezvoused and autonomously docked with the orbital lab’s Russian segment Zvezda service module on July 29, 2021.
The incident led to a temporary but major loss of ISS attitude control that the ground control team from NASA and Rosmosmos, the Russian space agency, managed to counter.
“There has not been risk from excessive loading. So that is good news,” Gatens told the committee. “We didn’t exceed structural loads. Teams in Russia and also an independent investigation team have been working to understand the root cause of why this happened and are finishing up those studies right now and will be releasing their reports very soon.”
The Zvezda module, which was launched in July 2000, is also undergoing a search for and repair of small air leaks traced to the tunnel portion of the module leading to a docking port for Russian Progress resupply capsules.
“The good news is there is a hatch that can seal off that area to minimize the loss of consumables,” Gatens said. “The crew has identified and permanently sealed one crack in the module and knocked down the leak rate by about half.”
The leak rate is now so small that efforts by the station crew to locate leak sites with a variety of ultrasonic detectors and even tea leaves floating in the absence of gravity has proven a challenge, she added.
On Nov. 30, NASA Inspector General Paul K. Martin issued a report calling on the agency to forego previously discussed plans for an extension of ISS operations beyond 2024 until it has isolated the source of and repaired the Zvezda module air leaks.
The agency disagreed, while estimating that experts on the ground should have a strategy for identifying and sealing the leaks by May 31, 2022.
On New Year’s Eve, NASA Administrator Bill Nelson announced the Biden administration was committed to an extension of NASA-led ISS operations through 2030.
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