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The Question

(Submitted May 05, 1997)

I'd like to find a list of visible satellites in the evening sky. I understand that there may be many, but I'm certain that several obvious ones would be noticeable.

The Answer

From any point on Earth, there are many visible satellites that pass over each night. Which satellites are visible, and when and where they appear, has to be calculated knowing the date and the location of the observer.

There are programs available to do these calculations, such as OrbiTrack for the Macintosh. Go to your favorite shareware and public domain site (e.g. and search for 'satellite'.

You will also need a list of current satellite 'elements' which describe the orbits of each satellite. These are provided by T. S. Kelso at The file has the most recent elements available, while the data for the Mir space station is in mir.tle . (tle stands for 'two line elements', because all the data for a satellite is written on two lines.)

With a program and a fresh data file (they lose accuracy after a few weeks) you can get a list of visible satellite passes in your area.

David Palmer
for Ask an Astrophysicist

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