ISS and Tiangong: what they share and how they differ

Published October 12, 2026 · Updated October 12, 2026

Two crewed stations at once

Right now there are two space stations with people living on board full time. One is the International Space Station, the ISS, continuously occupied since November 2000 and built through a partnership between the United States, Russia, Europe, Japan and Canada. The other is Tiangong (“Heavenly Palace”), China's station, completed in 2022.

Both circle Earth at about 400 km (250 miles) up, both can be seen with the naked eye from anywhere in the contiguous United States, and both serve the same purpose: living and running experiments in microgravity. But they're very different in size, in history and in the way they operate.

The comparison at a glance

Size: four times bigger

The ISS is much larger. It weighs about four times as much as Tiangong with its docked spacecraft, and it has a lot more living space, spread across more than a dozen modules. Tiangong, by contrast, is shaped like a T: a core module, Tianhe, with a lab on each side, Wentian and Mengtian. Its habitable volume is roughly a third of the ISS's.

That doesn't make Tiangong a lesser station when it comes to technology. Because it's so much newer, it was designed from the start with modern systems: high-efficiency water and oxygen recycling, robotic arms that can be joined together and next-generation solar panels. China has also announced plans to expand it with more modules.

The orbit: why Tiangong doesn't go as far north

An orbit's inclination sets the highest latitude a station reaches. The ISS's 51.6° was chosen so Soyuz spacecraft could reach it from Baikonur, in Kazakhstan. Tiangong's 41.5° is the best fit for its launch site at Jiuquan, in the Gobi Desert.

As a result, Tiangong never flies over anywhere north of 41.5° latitude. That's the latitude of Cleveland, and almost that of Chicago. You can see both stations from anywhere in the contiguous US, but from the far north (Seattle, northern Minnesota, northern Maine), Tiangong always appears toward the south and lower in the sky, topping out at around 20–30° above the horizon. Farther south, it can pass very high. The ISS, which reaches 51.6°, covers a wider band that takes in the entire contiguous US.

Crews and spacecraft

The ISS is normally home to seven people of several nationalities. They arrive on two spacecraft: Russia's Soyuz, from Baikonur, and SpaceX's Crew Dragon, from Florida. Since 2022, Russia and the US have been swapping seats, so some cosmonauts fly on Dragon and some NASA astronauts fly on Soyuz. We go into detail in how astronauts get to the ISS.

Tiangong houses three taikonauts (the name for Chinese astronauts), who arrive on Shenzhou spacecraft from Jiuquan and rotate roughly every six months. For a few days at each handover, the station has six people on board. Cargo goes up on Tianzhou spacecraft, launched from Wenchang, on Hainan Island.

Why China isn't part of the ISS

China was never part of the ISS. Since 2011, a measure passed by the US Congress, known as the Wolf Amendment, has barred NASA from working bilaterally with China's space program without explicit authorization. China chose to build its own station instead, following a step-by-step plan that began with two small test stations, Tiangong-1 (2011) and Tiangong-2 (2016).

Tiangong is open to experiments from other countries, and China has signed agreements to bring foreign astronauts on board. When the ISS is retired, around 2030, Tiangong may become for a while the only government-run station in orbit, alongside the commercial stations being prepared to replace the ISS. We cover this in the retirement and future of the ISS.

How to tell them apart in the sky

To the naked eye, they look the same: a bright dot that crosses the sky in a few minutes without blinking. The ISS is noticeably brighter because it's bigger and reflects more light; Tiangong looks more like a bright star than a planet. Our tracker follows only the ISS, so if you spot a moving dot that doesn't match any ISS pass, it could be Tiangong, another large satellite or a train of Starlink satellites. For those, see our guide Starlink vs. the ISS.

Frequently asked questions

Which station is bigger, the ISS or Tiangong?

The ISS, by far. It weighs about 420 metric tons (926,000 lb), compared with close to 100 (220,000 lb) for Tiangong with its docked spacecraft, and it has about three times as much living space.

Can you see Tiangong from the US?

Yes, from anywhere in the contiguous US. Its orbit reaches 41.5° latitude, the latitude of Cleveland and almost that of Chicago. From the far north (Seattle, northern Minnesota, northern Maine), it always appears to the south and lower in the sky, at around 20–30° at most. Farther south, it can pass very high.

How many people live on Tiangong?

Three, normally. During crew handovers, which happen roughly every six months, two crews overlap and there are six people on board for a few days.

Why isn't China part of the ISS?

Because a 2011 US law, the Wolf Amendment, bars NASA from working bilaterally with China's space program without the approval of Congress. China built its own station instead.

What will happen to Tiangong when the ISS is retired?

It will stay in service: it's designed to run for at least a decade. After the ISS is retired, expected around 2030, it will operate alongside the new commercial stations.