The brightest satellite in the sky is the International Space Station (ISS) — which makes sense, because it's the biggest. It's brighter than Jupiter and soon (with the addition of even more components) will regularly rival brilliant Venus as it creeps across your sky after dusk or before dawn.

You can see exactly when the International Space Station will be visible from your location by clicking on our Satellite Tracker. The predictions are custom-generated for your site. Just select your city (or enter in your latitude and longitude) and time zone and it will calculate potential passes for the next three days. You can even save your observing location for use at a later time.

This program will also show you in real time where ISS (as well as the Hubble Space Telescope or the Space Shuttle when it's in orbit) is over Earth. The current position of the selected spacecraft is shown, plus its ground track over the next hour at 5-minute intervals. The gray oval shows where the satellite is presently above the horizon.

When you look at the results, "Local Time" is the instant the satellite first becomes visible and is listed for your time zone. "Duration" indicates the length of each sighting in minutes. "Max. elevation" is how high the satellite will get above your horizon (90° is overhead). To see the spacecraft, look in the direction indicated by "Approach" at the given time. You should see a slowly moving "star" (weather permitting). The "Departure" entries indicate where the spacecraft will be when it vanishes from sight. Sometimes an appearance or disappearance occurs well up in the sky when the satellite emerges into sunlight or slips into Earth's shadow, respectively.

Construction of the ISS began on November 20, 1998, with the launch of the Russian-built module called Zarya ("Dawn"). The addition of two more core modules, Unity and Zvezda ("Star"), paved the way for the arrival of the first crew in November 2000. The U.S. laboratory module (Destiny), a large array of solar panels, and the Canada2 mobile robotic arm were added in 2001. From these modest beginnings, the ISS has continued to grow. An interesting collection of images that show changes in the configuration of the space station is on NASA's Human Spaceflight website.

The space station occupies an orbit roughly 250 miles (400 km) high, whose steep 52° inclination with respect to the equator causes it to pass over virtually all of Earth's populated areas.

Note: The Satellite Tracker is very computationally intensive and calculations sometimes take a few moments. If you are having run-time errors crop up when using Firefox, there is a simple fix:

(i) Type about:config in the address bar and press enter
(ii) Scroll down until you see dom.max_script_run_time
(iii) Double-click it and type in 30 seconds (the default is 10 seconds)
(iv) Restart Firefox

Click to open our Satellite Tracker.