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How to View the International Space Station from Earth

Stars and planets are not the only celestial bodies you can view from Earth. With simple equipment you can see The International Space Station, or the ISS.

You don’t need special equipment to make ISS sightings. Binoculars are adequate to view the ISS from Earth if you know the point at which the ISS is visible to the naked eye.

Viewing spacecraft from Earth adds unique opportunities for amateur astronomers. First, it provides a challenge. Viewing opportunities are fleeting, lasting only a few minutes; spacecraft can be challenging to locate as well.

Second, the knowledge that people are manning the spacecraft offers a thrill for star-gazers. The space station has been inhabited since its first crew entered it on Nov. 2, 2000.

The International Space Station

The space agencies of 15 countries contribute to the ISS project: the United States, Russia, Japan, Canada and 11 countries in Europe. Assembly began on the space-based research facility in 1998.

The ISS is essentially a merger of several planned space stations, including the U.S. Space Station Freedom and the Russian Mir Space Station.

Three main components make up the International Space Station:

Zarya Functional Cargo Block
Unity Module
Zvezda service module.

Eventually, the ISS will contain 14 modules that will serve the space station so that various scientific experiments can be conducted. Among the topics being studied are the effects of weightlessness and the physics of fluids in microgravity.

How to Observe the ISS

Because of its immense size, large solar wings and relatively low altitude, observers can often see detail and structure through binoculars (it moves too fast to be viewed easily through a telescope). When viewed from the ground without binoculars, the International Space Station looks like a pinpoint of bright, white light.

ISS tracking can be done at night because it, like other satellites and spacecraft, reflects the sun’s light back to Earth. Viewing times are best 45 minutes after sunset and 45 minutes before sunrise. These are times when the observer is in the dark but the ISS is in the sunlight.

Factors That Affect Visibility

Many factors affect visibility, but the two biggest are altitude and inclination.

Altitude is the height at which the spacecraft orbits the Earth. The lower the altitude, the brighter the space station will appear. Generally, the ISS orbits Earth at varying altitudes of 361 to 425 kilometers.

Inclination is the angular distance of the orbital plane to the plane of the Earth; it determines the spacecraft’s flight path. Generally, the best viewing comes when ISS travels at inclinations equal to or greater than the viewer’s latitude. The ISS typically appears at an inclination of 51.6 degrees.

The Earth’s own shadow is also a factor that limits visibility. It grows longer the nearer observers are to the equator. As a result, in June, you can view the ISS better north of the equator. In December, ISS sightings are clearer south of the equator.

The International Space Station Orbital Path Map

Observers need some guidance on exactly where to look to observe the space station. The International Space Station orbital path map is key to knowing when the ISS is visible. Observers do not have to be professional astronomers to use the International Space Station orbital path map. Computer software does all the work for you.

Thanks to sophisticated software at NASA Mission Control, the U.S. space agency lists ISS sighting opportunities. The software produces six columns of information about each satellite or spacecraft in its database:

The approach (the direction and elevation at which the spacecraft is expected to come into view)
The departure (the direction and elevation at which the spacecraft is expected to disappear from view).
The duration (length of time the spacecraft is expected to be visible)
The local date and time
The satellite/spacecraft name
The spacecraft’s maximum elevation above the horizon (measured in degrees where 90 degrees is directly overhead).

NASA also offers its SkyWatch program for users with more computer experience and broadband Internet connections. SkyWatch gives users minute-by-minute ISS sighting information and related data for improved ISS tracking. Another Web site, Heavens Above, also offers ISS tracking information.

Special Opportunities for ISS Sightings

ISS tracking can generate even more excitement when other spacecraft, such as a space shuttle, rendezvous with it. The International Space Station and the spacecraft docking with it will follow the same flight pattern on the days before the docking and days after the craft releases from ISS. The two spacecraft will appear to trail each as they move across the sky.

Another interesting display can come from routine dumping of waste water and discarded supplies. Waste water is typically released through nozzles. This action forms ice crystals, which appear as a comet-like tail. Dump schedules are also provided by NASA on its Web site.

Resources

European Space Agency (2006). See the ISS from Your Home Town. Retrieved March 18, 2008, from the European Space Agency Web site.

Molczan, Ted (2004). Observing Earth Satellites. Retrieved March 18, 2008, from the Visual Satellite Observer Web site.

National Aeronautics and Space Administration (n.d.). Sighting Opportunities: Sightings Help. Retrieved March 18, 2008, from the NASA Human Space Flight Web site.

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