Frequently asked questions and answers

1. Why do the pass predictions change from day to day?
The further the predicted ISS passes are in the future, the less accurate the predictions are. Since the orbital data is updated daily, the schedule may change slightly. Even the number of passes may change.
2. Is the ground view real-time video?
No. The current position of the ISS is displayed on maps derived by NASA from images taken by satellites, which is not real-time video. That is why you see the floor of the oceans and no clouds. However, the current position of the space station is real-time.
On board the ISS is a live web cam.
3. Is it the floor of the ocean that I see on the ground view when the ISS flies over the ocean?
Yes. The floor of the ocean is displayed like the satellite images have been processed by NASA.
4. Does the ISS website use cookies?
Yes. When you enter your location, it will be stored in a cookie on your computer. The next time you visit the website, your location will already be set for you.
5. Is the ISS completely assembled? How big is it? What does it weigh?
Find details at
6. Why is there a gap in the ISS's ground track?
The ground track is related to the next orbit which takes about 93 minutes. During that time the earth rotates below the ISS's orbit. That is why the ground track appears shifted westwards by about 23 degrees every orbit.
7. What does an ISS pass look like?
Have a look at this nice video provided by Francis Michel.
8. Why does the ISS's ground track look like a sine wave on the earth map?
The trajectory of the ISS is nearly a circle. When this circle is proyected on a flat map, it comes out as some sort of a sine wave.