The ISS orbits Earth about 15 times a day.
SOME things I just don't get tired of - watching my football team is one of them. Another is observing the International Space Station (ISS) fly by overhead. Rarely, however, do I get the opportunity to do both, but if the people in the MCG tonight look up at 8.45pm, they will see the ISS put on a spectacular performance as it glides silently through our sky. It will be as bright as Venus; bright enough to be seen despite the artificial light towers and difficult to miss. If you do miss it, you'll have more opportunities to see it during the next few days.
On Friday, begin looking for it at 7.47pm, Saturday at 8.26pm. Sunday will not be good but Monday it will become visible at 7.07pm.
All these passes will begin in the south-west sky and that's where you should begin your search. Tonight and Saturday will be the brightest. It usually takes less than five minutes to complete a pass, so if you have not seen it within that time frame, try again the next night.
This ISS is the largest object created by humans in space. Its dimensions are 108.5 metres by 72.8 metres. Compare that with the centre square of the MCG, whose four lines measure 45 metres a side. In fact, the ISS is larger than a full-size soccer pitch and weighs more than 450 cars. All this is whirling around the Earth about 27,000km/h - fast enough to complete 15 orbits a day at an average altitude of 370 kilometres. Six astronauts are on board at present.
More than half a million pieces of ''debris'' are in Earth's orbit, too, from tiny specks of paint to spanners and large parts of failed satellites.
This spells incredible danger for the ISS crew because at orbital speeds even the tiniest screw can become a lethal missile.
Last weekend the ISS crew sheltered in a docked Soyuz craft to make a quick escape should it be required. A ground crew had warned them that a piece of Cosmos satellite debris was going to pass the ISS. Eventually it rocketed past, missing the ISS by 14.8 kilometres, but in space you can never be too careful.
Professor Chris Tinney will give a free public talk on extra-solar planets tonight at 6.30pm at Monash University, Clayton campus, lecture theatre S3. Email Samantha.Penny@monash.edu for details. Follow Perry Vlahos' tweets @perryastronomy