The International Space Station is being built whilst in orbit above us. If it is sunlit when it passes over the UK during the hours of darkness it will appear as one of the brightest objects in the sky, moving fairly swiftly against the background of stars.

ISS orbits the earth every 90 minutes, 350km above our heads. An observer on the surface of the Earth sees only a very small fraction of the orbit. Under the very best conditions (clear horizon at zero degrees all round) the ISS will rise in the West and take less than 5 minutes to travel across the sky and set in the East. Most observers will only see it for about 3 minutes, so be sure to look out at the exact time of the predictions.

You can find out where to look and at what time TODAY by looking at the details for our set of nine towns in the UK. The predictions are given for today and for the next few days, both in outline form and in more detail. The detailed predictions show the estimated position of ISS in the sky at intervals of 30 seconds during each nighttime pass above the horizon.

Using our predictions, the satellite was seen by us at Herstmonceux during the early evening of Thursday, 14th December 2000. As predicted, the pass reached an elevation in the South of only 11 degrees above the horizon. It was seen as a fairly slow moving object fainter than Jupiter or Saturn, but nonetheless clearly visible. The pass took place about 35 seconds later than our prediction, due probably to manoeuvres onboard since the predictions were generated. The pass was video-recorded using a camera attached to the tracking telescope, and clearly showed the satellite moving relative to the background of stars. A still-frame from the video is seen here:

where the bright object is the ISS, and the two 'streaks' are images of stars which appear to move as the telescope tracks the satellite.

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