If you’re loath to get up at dawn to see the International Space Station (ISS) I don’t blame you. For an eclipse or meteor shower, yes, but probably not the ISS. The good news is that you only have to wait a bit till it comes round to the evening sky. And that’s now!
Now through about the first week of August (with some variation depending on location), you can watch the space station glide from west to east at dusk. During the next few evenings, many locations will have up to five passes a night much like we did back in late May. The first will be at dusk with subsequent passes spaced ~90 minutes apart until well after midnight.
The ISS always begins its runs low in the western sky and climbs the sky while heading east. It’s a brilliant, pale yellow “star” — at times rivaling Venus in brightness — that slips soundlessly across the constellations. Sometimes the station’s path crosses the southern sky, other times the north or even overhead, but it always travels west to east in the same direction as the Earth rotates. One complete pass from first easy appearance to disappearance takes about 6 minutes.
When first visible low in the west, the space station is not only ~250 miles high but far off in the distance, the reason it appears fainter than when overhead. As it climbs higher, it gets closer to us and shines brighter.
I used to think that the ISS reached peak brightness when it was overhead and just 250 miles away, but it’s typically brightest when it’s moved a short distance beyond the zenith into the eastern sky. At this position, the sunlight illuminates more of the station because it’s roughly opposite the sun the same way the sun lights up more of the moon as it approaches full. As the ISS continues east and drops lower in the sky, it begins to fade because its distance from the observer once again increases.
If you’re watching and see the station suddenly fade and then disappear, you’re seeing it eclipsed by Earth’s shadow. Have binoculars at the ready when this happens. As the ISS dims it changes color from pale yellow to deep red because from its point of view, the sun is setting.
You can find the space station and get a map showing its path by using Heavens Above. Click the link, select your city and then tap the ISS link. You’ll get a list of passes for the coming nights. Click on a date to see a map and timeline. Or you can go to NASA’s super-easy Spot the Station site for times. Lots of people like to use an app like ISS Spotter for iPhone and ISS Detector for Android.
During each pass, keep in your mind’s eye the six astronauts currently onboard of the Expedition 56 crew — five men and one woman under the command of Drew Feustel of Lake Orion, Mich. who specializes in seismology. The astronauts have been busy this week on fertility research and microbe studies as well as working on science gear to investigate advanced therapies for diseases such as Alzheimer’s and diabetes. Hey, it’s a job. But you sure can’t beat the view out the window.