Low Earth orbit (LEO) is an orbit around Earth with an altitude between 160 kilometers (99 mi) and 2,000 kilometers (1,200 mi). Most of the man-made objects in outer space are in LEO, including the International Space Station.

Objects in LEO are subject to atmospheric drag from the thermosphere (approximately 80–500 km) or exosphere (approximately 500 km and up), depending on the orbit height. This drag causes the orbit to decay over time, which is why the ISS requires periodic "re-boosts" to maintain its altitude.

The ISS orbits at an average altitude of 400 km. At this height, it travels at a staggering speed of 7.66 km/s (27,600 km/h), completing one revolution around Earth every 90 minutes. This means astronauts on board witness 16 sunrises and sunsets every single day!

Spotting the International Space Station is an incredible experience that requires no special equipment—just your eyes and a clear sky. Because of its size (roughly the size of a football field) and highly reflective solar panels, it is the third brightest object in the sky after the Sun and Moon.

Key Tips for Sightings:

• Timing is Everything: The ISS is best seen just after sunset or just before sunrise. This is because the station is high enough to still be in sunlight, while you are in the dark on the ground.
• Look for a Steady Light: Unlike airplanes, the ISS does not have blinking lights. It looks like a very bright, steady star moving across the sky.
• Speed: It moves much faster than a typical airplane, crossing the sky in about 2 to 6 minutes.
• Direction: Use our Compass View to find the exact bearing and elevation for your next pass.

The ISS is a unique laboratory where researchers from around the world conduct experiments that would be impossible on Earth. The "weightless" environment allows for breakthroughs in medicine, materials science, and fundamental physics.

For example, protein crystals grown in microgravity are often larger and more perfect than those grown on Earth, helping scientists design better drugs for diseases like cancer and Alzheimer's. Additionally, studying how the human body adapts to long-duration spaceflight is critical for our future missions to Mars.

After decades of service, NASA has announced plans to deorbit the International Space Station in early 2030. The station will be guided into a remote part of the Pacific Ocean known as Point Nemo, the "spacecraft cemetery."

While the end of the ISS marks the end of an era, it also paves the way for commercial space stations. Companies like Axiom Space and Blue Origin are already developing private modules and stations that will continue the legacy of human presence in low Earth orbit.

• 1957: Sputnik 1, the first artificial satellite, is launched by the Soviet Union.
• 1961: Yuri Gagarin becomes the first human in space.
• 1969: Apollo 11 lands the first humans on the Moon.
• 1998: The first module of the ISS, Zarya, is launched.
• 2021: The James Webb Space Telescope is launched to peer into the deep universe.