We’re back in another great evening run of International Space Station (ISS) passes. Now through early August there will be 2-3 flybys on most nights with a as many as four on some. Each year within a few weeks of summer solstice in either hemisphere, the space station’s orbit and line separating day from night on our planet nearly align. For a few days and nights, the ISS orbits in constant or nearly constant sunlight; the astronaut crew and their craft bask in sunlight 24/7 like Arctic residents in the midnight sun. Back down on Earth every time the station makes a pass, we see it, making for multiple passes during the night.
The Northern Hemisphere “midnight sun” season happens between May and July; southern observers get their turn between November and January. And now that the moon is departing the evening sky, the ISS will really stand out against the stars. Remember that unlike those luminaries it rises in the western sky and sets in the east. That’s because it was launched into orbit to take advantage of Earth’s rotation. Earth rotates from west to east in the same direction, so the station picks up about 915 mph (1,470 km) in free speed. That means less fuel and less money.
The first ISS pass usually occurs in early twilight in a deep blue sky. The second happens about an hour and a half later in a dark sky. That’s how long it takes to circle Earth’s circumference of 24,900 miles (40,000 km) traveling at more than 17,000 miles an hour (27,350 km/hour). And yet the astronauts feel no sense of speed for the same reason you can close your eyes in an airplane traveling at 500 mph and feel like you’re sitting still — everything around you is traveling at the same speed. Everything stays put. Only if your speed were to suddenly change — slow down or speed up — would you sense motion.
There’s a full house on board the station at the moment with a with five men and one woman. To date 566 people have traveled to space, the vast majority to the ISS. The Expedition 60 crew will spend more than six months conducting about 250 science investigations in biology, Earth science, human research, physical sciences, and technology development. What they learn will enable long-duration and robotic exploration of the Moon and Mars in future missions.
One of the biggest changes at the station will be the arrival of a second docking port for SpaceX’s Crew Dragon and Boeing’s Starliner. The two are competing to provide transportation for American astronauts to the ISS. Since the end of the space shuttle program, U.S. astronauts have been dependent on the Russian Soyuz spacecraft for a lift.
On Wednesday, July 24, a SpaceX Dragon resupply mission will launch to the station with supplies and materials for all those science experiments. But it will also carry a docking adaptor to provide two common ports for visiting vehicles. It may be possible to see the Dragon chase the space station on Wednesday and Thursday nights as closes in for an early Friday morning docking. If so I’ll update you with times on when to see them both.
You can know when and where to look for the space station as well as print out a map of its path at Heavens Above. Click the link, select your city and then tap the ISS link for a list of passes for the coming nights. Click on a date to see a map and timeline. Or go to NASA’s super-easy Spot the Station site for times. You can sign up there to get e-mail or text alerts whenever there’s a favorable pass over your city. You can also use an app like ISS Spotter for iPhone or ISS Detector for Android. Both will show the times and even alert you to favorable passes. Oh, and they both cost nothing.
Happy spaceship hunting!