U.S.-Russian ISS Commission: Controlled Deorbit, No Gap, are Imperatives

The U.S.-Russian Joint Commission that advises NASA and Roscosmos on operations of the International Space Station is stressing the need for a planned, controlled deorbit of the ISS at the end of its lifetime. Both primary and backup deorbit capabilities must be in place before the two-and-a-half year orbit-lowering process begins. That would put the ISS into the Pacific Ocean at the end of 2030. They also want to ensure there is no gap between ISS and whatever replaces it to ensure research critical to supporting human missions to the Moon and Mars continues uninterrupted.

The Joint Commission, a combination of NASA’s International Space Station (ISS) Advisory Committee and Roscosmos’s Advisory Expert Council, met at NASA’s Johnson Space Center from February 18-21, 2025.

The NASA committee is chaired by Bob Cabana, a former astronaut, former Director of Kennedy Space Center, and former NASA Associate Administrator who retired from the agency at the end of 2023. Today Cabana provided a public recap of their findings and recommendations.

A partnership among the United States, Russia, Japan, Canada and 11 European countries working through the European Space Agency, the first two modules were launched in 1998 and it’s been permanently occupied by international crews rotating on roughly six month schedules for more than 24 years.

In short, the ISS is old. And showing it. Persistent air leaks were first detected in 2019 in a tunnel that connects Russia’s Service Module to a docking port for Progress cargo vehicles — dubbed PrK. They are ongoing and a source of worry not only to the Joint Commission, but NASA’s Aerospace Safety Advisory Panel.

All of the partners except Russia have agreed to operate the ISS until 2030. Russia is formally committed only through 2028, but NASA expects them to extend that to 2030 in due course. The questions are whether it will remain safe for human occupancy that long, what’s the deorbit plan, and what comes next to ensure microgravity research continues.

At the Joint Commission’s last meeting in September 2024, the U.S. and Russian sides couldn’t agree on the root cause of the leaks or the risk they pose.  NASA is more concerned than Roscosmos and requires that the hatch between the Russian and U.S. segments be closed whenever cosmonauts open the hatch to that docking port.  In response to a recommendation from the Joint Commission in September, the two space agencies agreed to bring in independent experts from industry and academia to assist in diagnosing the problem.

Cabana said they were told at this meeting that their recommendation is being executed and a NASA-Roscosmos team will meet in Moscow next month “to exchange data and better understand the problem.”  But it doesn’t appear much progress has been made since the last meeting.  The Joint Commission said today simply that they support “face-to-face meetings of U.S. and Russian materials and structural experts to find a common understanding of the leaks.”  Once that’s determined, they want the space agencies to “reevaluate the nominal and contingency procedures on orbit.”

Assuming nothing catastrophic happens before 2030, the plan is to use a U.S. Deorbit Vehicle, or USDV, to intentionally deorbit the ISS into a remote part of the Pacific Ocean at the end of its lifetime. The Joint Commission wants a secondary deorbit capability in case something goes awry with the USDV. The contingency plan is using two Russian Progress cargo vehicles and the Russian segment itself to dispose of the ISS. That requires ensuring the propellant tanks on the Russian segment are full. Cabana said they reviewed a plan to have the tanks on the Zvezda Service Module and Zarya Functional Cargo Block (FGB) “sufficiently filled by 2028,” the same year the USDV should arrive so the two-and-a-half year process to slowly lower the orbit can begin.

“The Joint Commission agreed that to ensure public safety with a safe deorbit of the ISS, lowering the ISS altitude cannot start until 2028 when the critical capabilities are expected to be available. This results in ISS reentry no earlier than late 2030.” — Bob Cabana

They asked NASA and Roscosmos to come up with “an integrated deorbit decision timeline” that takes into account safety milestones, hardware readiness, and the availability of critical capabilities.

No mention was made during Cabana’s outbrief of Elon Musk’s comments that the ISS should be deorbited two years from now instead of 2030. That doesn’t appear to be a safe option based on the timeline Cabana laid out. Musk’s SpaceX is building the USDV under a $843 million contract with NASA, not including launch. Unlike the Cargo Dragon and Crew Dragon spacecraft SpaceX developed through Public-Private Partnerships with NASA that it owns and operates, the USDV will be owned and operated by NASA.

Keeping the ISS operating and then safely deorbiting it into the ocean in 2030 still leaves the question of what comes next.

Cabana emphasized the “critical” importance of the research being conducted on ISS for future human spaceflight and shared an intriguing scientific finding — microbiological growth has been found on exterior space station surfaces. “These microorganisms seem to be genetically identical to terrestrial organisms” and may have been transported there by the “tiny amount of atmosphere” at that altitude.  “It’s surprising” they exist and underscores the importance of continued research.

“Knowledge gaps in both human biological research and fundamental science will require further study for the safety of future human spaceflights, including to the Moon and Mars.  For example, eye and possibly brain changes have been observed in astronauts during long duration spaceflight. The precise cause of these changes is not yet known, nor are there currently any valuable mitigations or treatments. We should continue to find new observations as we continue to extend the limits of human exploration in space.” — Bob Cabana

The Joint Commission wants to accelerate research on the ISS and ensure future space stations are in place before the ISS is deorbited.

“It is critical to continue the uninterrupted joint international scientific and engineering work, having a continuous human presence with no gap for human laboratories in low Earth orbit to enable success of future human missions to low Earth orbit, the Moon and Mars.” — Bob Cabana

Cabana is one of four former NASA astronauts on the ISS Advisory Committee who were on the call today. The others were Frank Culbertson, Bill Shepherd and Mark Vande Hei.  Cabana commanded the space shuttle mission, STS-88, that delivered the first ISS module (Node 1 or Unity) to orbit.  Shepherd was the U.S. astronaut on the three-person crew that initiated permanent occupancy of the ISS on November 2, 2000, along with Russia’s Sergei Krikalev and Yuri Gidzenko.

Culbertson led the U.S. side of the Shuttle-Mir program in the 1990s when U.S. astronauts flew to Russia’s Mir space station and Russian astronauts flew on the U.S. shuttle.  He was aboard the ISS on Expedition 3 on September 11, 2001 when terrorists attacked the United States and has shared moving recollections of what it was like to be in space watching the tragedy unfold. Vande Hei is one of several astronauts and cosmonauts who ended up staying on the ISS longer than expected setting what was then a U.S. record of 355 continuous days in space in 2022 (Frank Rubio surpassed that in 2023 at 371 days, another unexpectedly extended mission).

NASA’s Advisory Committee Management Division’s website doesn’t list the members of this committee and the committee’s own website shows only its charter. Cabana was the only committee member who spoke during the approximately 15-minute presentation. According to the roll call taken at the start of the meeting, former NASA astronaut Nicole Stott is also a member, but wasn’t present today (nor was Ginger Kerrick).  Other members who were there: Bill Vantine, Chuck Daniel, Dan Heimerdinger, Harmony Myers, and Joe Schmid. Most but not all were members at the last meeting according to the minutes.