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## Frequently Asked Questions About 

# **The International Space Station**

The International Space Station Program brings together international flight crews, multiple launch vehicles, globally distributed launch, operations, training, engineering, and development facilities, communications networks, and the international scientific research community. Launched in 1998 and involving the U.S., Russia, Canada, Japan, and the participating countries of the European Space Agency — the International Space Station is one of the most complex international collaborations ever attempted. 

Who operates the ISS?

What are some examples of how the ISS is interdependent?

What areas of Earth does the ISS fly over?

Can astronauts fly to the ISS on one type of spacecraft and return on a different one?

Do NASA and Roscosmos always need its astronauts or cosmonauts on the ISS? 

How is the attitude and altitude controlled and can any current functions be replaced or upgraded?  

How long do all the ISS partners plan to operate the complex?

How will NASA and Roscosmos safely deorbit the ISS after its planned decommissioning?

### **Who operates the International Space Station?**

Five partner agencies (the Canadian Space Agency, the European Space Agency, the Japan Aerospace Exploration Agency, the National Aeronautics and Space Administration, and the State Space Corporation “Roscosmos”) operate the International Space Station, with each partner responsible for managing and controlling the hardware it provides. The station was designed to be interdependent and relies on contributions from across the partnership to function. No one partner currently has the capability to function without the other. 

The space station was not designed to be disassembled, and current interdependencies between each segment of the station prevent the U.S. Orbital Segment and Russian Segment from operating independently. Attempts to detach the U.S. Orbital Segment and the Russian Segment would encounter major logistical and safety challenges given the multitude of external and internal connections, the need to control spacecraft attitude and altitude, and software interdependency. 

### **What are some examples of how the International Space Station is interdependent?**

Examples include: - Russia provides all of the propulsion for International Space Station used for station reboost, attitude control, debris avoidance maneuvers and eventual de-orbit operations by the Russian Segment, Russian propulsion systems, and Progress resupply cargo spacecraft. 
- Propellant for thrusters on the Russian Segment is supplied by Russian Progress cargo spacecraft. 
- The U.S. gyroscopes provide day-to-day attitude control to control the orientation of the station. Russian thrusters are used for attitude control during dynamic events, like spacecraft dockings, and provide attitude control recovery when the gyroscopes reach their control limits. 
- Power from the U.S. solar arrays is transferred to the Russian Segment to augment their power needs. 
- NASA’s Tracking and Data Relay Satellites (TDRS) provide communications and data transfer capability between the ground and the entire station, with some additional, less-continuous capability through Russian ground stations and satellites. 

### **What areas of Earth does the International Space Station fly over?**

The International Space Station orbits with an inclination of 51.6 degrees. This means that, as it orbits, the farthest north and south of the Equator it will ever go is 51.6 degrees latitude. An explanation and visuals of the space station orbit is available online. 

On the Spot The Station page, you can enter a country or region to watch the International Space Station pass overhead from several thousand worldwide locations. 

### **Can astronauts fly to the International Space Station on one type of spacecraft and return on a different one?**

Astronauts typically launch and return in the same type of spacecraft (i.e., Crew Dragon or Soyuz).  Each astronaut has custom hardware including a launch and entry suit or a seat liner that is not interchangeable between different models of spacecraft. A crew member can launch on one Russian Soyuz and return on a different Soyuz, but transferring them to return on a SpaceX Dragon would require a different launch and entry suit that is custom fitted and created on the ground. NASA astronaut Mark Vande Hei has transferred seat liners between Soyuz spacecraft on his record setting mission. 

### **Do NASA and Roscosmos always need its astronauts or cosmonauts on the International Space Station?** 

Operating the space station requires physical, hands-on maintenance by the crew, on both U.S. Operating Segment and the Russian Segment, to ensure systems continue functioning. NASA and Roscosmos crew members are not trained to operate each other’s respective segments without onboard assistance. In failure scenarios on the United States Orbital Segment, only U.S. astronauts are trained to fully respond, either through actions inside the station (e.g., to change out a component) or through spacewalks. The same is true for Russian cosmonauts in failure situations originating on the Russian segment. 

### **How is the International Space Station’s attitude and altitude controlled and can any current functions be replaced or upgraded?** 

All International Space Station propulsion is provided by the Russian Segment and Russian cargo spacecraft.  Propulsion is used for station reboost, attitude control, debris avoidance maneuvers and eventual deorbit operations are handled by the Russian Segment and Progress cargo craft. The U.S. gyroscopes provide day-to-day attitude control or controlling the orientation of the station. Russian thrusters are used for attitude control during dynamic events like spacecraft dockings and provide attitude control recovery when the gyroscopes reach their control limits. 

Northrop Grumman’s Cygnus is the only U.S. commercial spacecraft currently in testing to provide limited capability for future reboosts. This capability relies on the Russian Segment for attitude control during the small reboost. It does not currently have the capability to replace attitude control functions for the space station or carry adequate propellant for long-term sustained operations. 

Attitude control and propulsive reboost capability is a continuous requirement, which means the space station needs a continuous and steady supply of propulsion spacecraft. Changes to the current propulsion scheme would take considerable new hardware/software development, and significant time and funding to enact. 

### **How long do all the International Space Station partners plan to operate the complex?**

NASA and its international partners have maintained a continuous and productive human presence aboard the International Space Station for more than 21 years. Life extension analysis for the US Segment has been completed through 2028 with no issues that would prevent space station from being further extended.  The United States has committed to extend International Space Station operations through 2030. NASA’s space agency partners have all recommended International Space Station extension through 2030 with approvals pending through their own government processes. 

### **How will NASA and Roscosmos safely deorbit the International Space Station after its planned decommissioning?**

The primary objective during space station deorbit operations is the safe re-entry of the space station’s structure into an unpopulated area in the ocean as outlined in the agency’s International Space Station transition plan. 

The space station will accomplish the deorbit maneuvers by using the propulsive capabilities of the space station and its visiting spacecraft. NASA and its partners have evaluated varying quantities of Russian Progress spacecraft to support deorbit operations. Additionally, NASA is evaluating whether U.S. commercial spacecraft can be modified to provide capability to deorbit the space station. 

Read our International Space Station transition plan FAQ page. 

## Discover More Topics From NASA

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