The International Space Station (ISS) takes about 90 minutes to orbit the Earth. Because of its inclination of 51.6° it “flies” above any single place (between +51.6° and -51.6° latitude) a few times a day. Nonetheless, the station can be observed from the ground only under right conditions – shortly before sunrise or after sunset when the sky is darkened and sun light reflects from the station before it slides into the night.
Today, two passes were observable from the UK’s capital. The first started a few seconds after 18:51 UT and the station reached the altitude of 10° after 2 minutes (at around 18:31:30UT). It passed through the constellations of Eridanus, Orion, Gemini, Canis Minor, Cancer and Leo where it slowly sank into Earth’s shadow. At the maximum brightness, ISS was twice as bright (approx -2.0 mag) as the brightest star in the night sky, Sirius (-1.46 mag).
The second pass, during the station’s next orbit, wasn’t as glorious as the first. The station climbed over the horizon at 20:26 UT but wasn’t observable until it reached the altitude of about 10-15° at around 20:29 UT and appeared from behind the fog and light pollution.
I took the picture above with the digital camera on my Nokia N96. As you can imagine, light pollution is terrible in London. It wasn’t before some image reduction (using dark frames) that the captured station clearly appeared. I used the camera set to 800 ISO, decreased contrast (I wish I had remembered the black & white option) and in the burst sequence mode. Unfortunately, after 20 photos, the phone couldn’t store the raw image data in the buffer any more and began writing the data to disk effectively turning the camera to stand-by. At that point all I could do was to enjoy the show through my own eyes.
One piece of good news is that before a blackout window from April 1 through April 22 during which the ISS will not be observable from London, no less that eight majestic passes, each showing the ISS brighter than -2 mag, will be visible. More information about ISS visibility (for any location on the planet) can be found on Heavens Above.
As the ISS passed above London, I also watched the astronauts aboard the station during a live video broadcast on NASA TV. It was an interesting experience hearing the crew in TV while watching the station pass through Orion and reach -2.4 mag. During the conference, the crew answered questions about the recent debris collision alerts and described the view from the station. Apparently, astronauts can not only see the continents, mountains and cities but also airports, bridges and even some buildings. The Expedition 18 commander Mike Fincke talked about the tremendous value of international cooperation in projects such as the ISS and compared it to the utopian society from the Star Trek universe. He also answered an frequently asked question: it is impossible to see the Great Wall even under ideal weather conditions despite its length (over 6400km). The wall is not that wide, and made from native materials that match the color of the surrounding landscape.