Night sight not to be missed

Watching them watching you: the East of England as seen by the scientists aboard the ISS

If you look up into the evening sky over Rye for the next few weeks there is a chance you might see a surprisingly bright light moving steadily from the western horizon towards the east. Its exact brightness and angle of trajectory will vary. On some nights you might observe it passing directly overhead with a brightness greater than that of the planet Venus. Often it is possible to see it through thin cloud or even if you are standing near streetlights. This bright object is easily distinguished from the many aircraft passing below it as it carries no flashing coloured beacons and travels in silence.

As you watch this point of light passing across the sky above you, you might be interested to consider this: the object you are looking at is travelling in the region of 17,100mph, at an altitude of about 250 miles above the earth’s surface. As you watch it approaching, climbing from an angle of about 10 degrees above the horizon, it is still travelling out over the Atlantic Ocean beyond the west coast of Ireland. Once it has passed overhead and begins descending towards the east it will already be moving away down over mainland Europe. If you happen to be in an open space, like Pett Level or the Rye Harbour Nature Reserve, you will be able to observe its whole trajectory across the sky for about 10 minutes. However, on some nights you might observe that the bright light will prematurely begin to fade and eventually disappear back into the darkness of the sky, as it enters into shadow.

Orbiting scientific lab

If you watch this object regularly you might notice that it sometimes follows, or is followed by, another much dimmer point of light, still easily visible with the naked eye. This object appears to move in tandem with it, in the same orbit, at the same speed. The bright object you are looking at is the International Space Station (ISS), funded and supported by international collaboration led by America, Russia and Europe. The occasional dimmer one accompanying it is likely to be an automated, unmanned supply ship, either preparing to arrive or departing from the station. Out there in the unforgiving harshness of space above us, the ISS is a large, fragile, vulnerable assembly of interconnected modules that together make up the most technically complex and expensive machine in existence. It is both an orbiting scientific laboratory and observation platform. Currently it is home to six people for the next six months.

Every 24 hours the station completes approximately 16 orbits of the earth – or one orbit nearly every 90 minutes. Moving from west to east it crosses the equator at an angle of 51.6 degrees. However, owing to simultaneous rotation of the planet below it, the station changes the latitude of its orbit by about 22.9 degrees each time. This explains why, on a typical clear evening, you may be lucky enough to see the ISS passing through the sky up to three times, but on each occasion the angle of view will change.

Ideal for earth observations

This constant variation of latitude means that the orbit of the station will cover most points on the surface of the planet, making it an ideal scientific platform for earth observations. It also explains why, as a ground-based observer in and around Rye, you will be able to observe the ISS, cloud allowing, in the early evening for only a couple of weeks before it disappears from view. After that it will then vanish into daylight for two weeks as it crosses the UK, later reappearing for two weeks in the early morning, and then disappearing again for another two weeks into shadow during the middle of the night. Once this two month cycle is complete you can see it again in the evening.

Like the much less sophisticated space stations that preceded it, such as the Russian MIR and American Skylab, this station will also have a finite lifespan. But, unlike these previous stations, which were allowed to burn up harmlessly in the earth’s atmosphere as their orbits naturally decayed, the end of the ISS is likely to be determined by the machinations of international politics. Already, as a direct result of America’s recent implementation of economic sanctions against Russia, the government has announced it will no longer support the ISS project beyond 2020. Exactly what will happen to the ISS complex after this time remains unclear. Possible future plans have included the idea of decoupling the American and European modules and placing them in a new orbit around the moon.

Last of its kind

For now, as you watch the ISS passing over Rye, arcing from west to east over the Monastery, Landgate tower and St Mary’s church, familiar structures in our town that are nearly 1,000 years old, consider this. The human race has reached a watershed moment with this technology, which is only just over 50 years old. The space station that you are observing may be one of the last great civilian, non-military space projects to be funded exclusively by national governments, in the West at least, as private companies and fantastically rich entrepreneurs reach out into space. As a result, a future space station might be a commercial enterprise and, rather than being just an orbiting scientific laboratory, is also likely to become an intermediate staging post for expeditions to or settlement of the moon, and eventually manned voyages out to Mars and beyond.

The current space station, as it passes silently overhead at 22 times the speed of sound, is a fine sight on a clear night, passing through the vast open skies over Rye and the surrounding marsh country. For myself, I remember an occasion earlier in the year when I was privileged enough to see it one clear night from the Gun Gardens in Rye. As I watched I saw it cross the line of the planets Mars, Jupiter and Saturn and then a full moon. Soon afterwards a single brilliant shooting star, descending at huge speed through the constellation of Leo, flared momentarily right across its path.

All the information you need to view the ISS can be found at this non-profit website. Remember to input your location to get precise viewing details.