Overview
The International Space Station is a modular structure assembled in orbit over more than a decade, from the launch of its first component in 1998 to the final major module arrival in 2021. Built by five space agencies — NASA, Roscosmos, ESA, JAXA and CSA — the ISS consists of 16 pressurised modules enclosing approximately 916 m³ of pressurised volume, of which about 388 m³ is habitable crew space. Around that core sits an integrated truss structure spanning 109 metres, plus extensive external platforms for experiments and equipment.
The module count covers pressurised elements currently in the on-orbit configuration. The tables below also list the docking adapters and the Pirs compartment, which was deorbited in 2021 and is no longer part of that count. Habitable volume is the crew-accessible space inside those modules; the 916 m³ figure is total pressurised volume, including racks, stowage and equipment bays.
Aboard now: Jessica Meir, Anna Kikina, Pyotr Dubrov, Jack Hathaway, Anil Menon, Andrei Fedyaev, Sophie Adenot. The station is travelling at 27,598 km/h.
Which docking ports are occupied right now
The ISS has a fixed set of berths, and every visiting vehicle takes one of them. This is what is attached at the moment, and to which port.
| Vehicle | Type | Port | Docked | Attached for |
|---|---|---|---|---|
| Soyuz MS-29 | Crew | Prichal nadir | 14 Jul 2026 | 2 months |
| Progress MS-34 | Cargo | Zvezda aft | 28 Apr 2026 | 4 months |
| Cygnus NG-24 | Cargo | Unity nadir | 13 Apr 2026 | 5 months |
| Crew Dragon Freedom | Crew | Harmony zenith | 14 Feb 2026 | 7 months |
Crew, port occupancy, altitude and period are read from live tracking data when the page is served. Module ages count from each element's launch date.
US Orbital Segment (USOS)
The US Orbital Segment includes modules contributed by NASA, ESA, JAXA and CSA. These form the primary laboratory and habitation areas of the station.
| Module | Agency | Launch | Time in orbit | Role |
|---|---|---|---|---|
| Unity (Node 1) | NASA | Dec 1998 | 27y 9m | First US element; six-port connecting node linking the Russian and American segments |
| Destiny | NASA | Feb 2001 | 25y 7m | Primary US research laboratory — microgravity science, life sciences and materials experiments |
| Quest | NASA | Jul 2001 | 25y 2m | Joint airlock — enables EVAs (spacewalks) using both US EMU and Russian Orlan suits |
| Harmony (Node 2) | NASA / ESA-built | Oct 2007 | 18y 10m | Utility hub connecting Columbus, Kibo and crew transfer vehicles; provides power and data |
| Columbus | ESA | Feb 2008 | 18y 7m | European research laboratory — fluid physics, materials science, biology and external experiments via the EPF |
| Kibō (JEM) | JAXA | Mar–Jul 2008 | 18y 6m | Japan's laboratory complex — the largest single ISS module, including pressurised lab, logistics module, exposed facility and robotic arm |
| Tranquility (Node 3) | NASA / ESA-built | Feb 2010 | 16y 7m | Life support and crew exercise; hosts the Cupola and ARED exercise machine |
| Cupola | ESA | Feb 2010 | 16y 7m | Seven-window observation dome — used for Earth observation, robotics operations and photography |
| Leonardo (PMM) | NASA / ASI | Feb 2011 | 15y 6m | Permanent multi-purpose module — storage for supplies, equipment and experiments |
| Bigelow BEAM | NASA / Bigelow | Apr 2016 | 10y 5m | Expandable technology demonstrator — inflatable habitat module, now used for storage |
| IDA-2 & IDA-3 | NASA | 2016 / 2019 | 10y 2m | International Docking Adapters — NDS-standard ports for Crew Dragon and Starliner |
| NanoRacks Bishop | NanoRacks | Dec 2020 | 5y 9m | Commercial airlock — deploys CubeSats and transfers experiments to/from the vacuum of space |
Russian Orbital Segment (ROS)
The Russian segment provides critical propulsion, life support and docking capabilities. It includes the station's oldest module and the most recently launched pressurised element.
| Module | Agency | Launch | Time in orbit | Role |
|---|---|---|---|---|
| Zarya (FGB) | Roscosmos / NASA-funded | Nov 1998 | 27y 9m | First ISS component launched — provided initial propulsion, power and attitude control; now primarily used for storage |
| Zvezda (SM) | Roscosmos | Jul 2000 | 26y 2m | Service module — crew quarters, life support, propulsion and orbital reboost engines; the structural and functional centre of the Russian segment |
| Pirs (DC-1) Removed | Roscosmos | Sep 2001 | 2001–2021 (removed) | Docking compartment and airlock for Russian EVAs and Soyuz/Progress vehicles. Undocked and deorbited in July 2021 to free the Zvezda nadir port for Nauka, so it is no longer part of the 16-module count. |
| Poisk (MRM-2) | Roscosmos | Nov 2009 | 16y 10m | Mini research module — docking port for Soyuz/Progress and airlock for Russian EVAs |
| Rassvet (MRM-1) | Roscosmos | May 2010 | 16y 4m | Docking and cargo storage module — attached to Zarya's nadir port |
| Nauka (MLM) | Roscosmos | Jul 2021 | 5y 1m | Multipurpose laboratory module — the largest Russian ISS module, with European Robotic Arm (ERA), additional crew quarters, science facilities and an airlock |
| Prichal | Roscosmos | Nov 2021 | 4y 9m | Node module — six-port docking hub attached to Nauka, expands docking capacity for visiting vehicles |
Integrated Truss Structure
The ISS truss is a 109-metre backbone of aluminium segments that supports the station's four pairs of solar arrays, thermal radiators, batteries and external experiment platforms. The truss was assembled across 11 Space Shuttle flights between 2000 and 2009. The original arrays measure 73 metres tip to tip and the eight of them together supply roughly 75 to 90 kW of usable electrical power. Since 2021 a programme of smaller iROSA roll-out arrays has been progressively installed over the older wings, recovering capacity lost to two decades of degradation; eight are planned in total, one for each power channel. That whole assembly is what makes the ISS visible from Earth as a bright, slow-moving point of light.
Adapters, Platforms and External Facilities
Not everything bolted to the station is a module. Three other families of hardware matter for understanding how the ISS actually works, and they are the pieces most often missing from module lists.
Pressurised Mating Adapters (PMA-1, PMA-2, PMA-3)
The PMAs are short conical tunnels that mate the Russian and American docking standards and provide the station's forward berths. PMA-1 permanently joins Zarya to Unity, making it the physical seam between the Russian and US segments. PMA-2 (Harmony forward) and PMA-3 (Harmony zenith) each carry one of the International Docking Adapters, which is how Crew Dragon and Starliner arrive. They are pressurised and crew-accessible, but they are adapters rather than modules, which is why they sit outside the 16-module count.
Kibō's other two parts
Kibō is usually listed as one module but is really a complex of three. The Pressurised Module is the laboratory proper; the Experiment Logistics Module – Pressurised Section (ELM-PS) is a storage loft mounted on top of it; and the Exposed Facility is an external porch holding experiments directly in vacuum, serviced by Kibō's own robotic arm. Together they make Kibō the largest single contribution to the station by any one agency.
External platforms: Bartolomeo, ELCs and ESPs
Payloads that need vacuum, not pressure, live on external platforms. Bartolomeo, added to the front of ESA's Columbus laboratory in 2020, offers commercial payload slots with Earth and deep-space views, and is the newest significant addition to the US segment. The four ExPRESS Logistics Carriers (ELC-1 to ELC-4) and the External Stowage Platforms hold spare parts and experiments along the truss: unglamorous, but they are the reason the station can replace failed hardware without waiting for a launch.
What Comes After the ISS
The station's replacement is already being assembled in contracts if not yet in orbit, and the first pieces are designed to arrive while the ISS is still flying.
Axiom Station is the only successor designed to begin life attached to the ISS. Axiom Space plans to berth its first module to Harmony's forward port, add further habitat, research and manufacturing modules, and then detach the assembly as a free-flying commercial station before the ISS is deorbited. Other contenders, including Orbital Reef and Starlab, are designed as standalone stations from the outset. You can follow all of them on our commercial space stations page, or compare the current generation on the space stations hub.
The practical consequence for this page is that the ISS module list is now a closed set. No further permanent modules are planned for the station itself; every addition from here is either an external platform, a replacement solar array, or hardware that is intended to fly away again.
Assembly Timeline
Construction of the ISS required more than 40 assembly flights — 37 Space Shuttle missions and numerous Russian Proton and Soyuz launches. The first element (Zarya) launched on 20 November 1998 aboard a Russian Proton-K rocket. The station was declared "assembly complete" in 2011, though new elements have continued to arrive, most recently Nauka (2021) and Prichal (2021). Under the partner agreements currently in force the station is funded to operate to 2030, with a controlled deorbit to follow; NASA has contracted a dedicated US Deorbit Vehicle for that manoeuvre.
Current Configuration
The ISS has a total mass of approximately 420,000 kg and is crewed continuously, with 7 people aboard right now across NASA, Roscosmos, ESA, JAXA and CSA rotations. It is orbiting at 420 km and completes one orbit every 92.9 min at 27,598 km/h. 4 vehicles are docked right now. Visiting vehicles currently include SpaceX Crew Dragon, SpaceX Cargo Dragon, Northrop Grumman Cygnus, Roscosmos Progress and Soyuz. You can follow its position in real time on our live ISS tracker.