Space Station Makes July Dusk Debut

Flight Engineers Peggy Whitson and Jack Fischer assess spaceflight-induced changes in muscle volume on the space station this week. Credit: NASA

Just a reminder that the International Space Station (ISS) will be making evening passes for about the next two weeks for many areas in the northern hemisphere. It’s just getting warmed up late tonight with a post-midnight flyby; convenient evening viewing times start tomorrow. Once you know the time the ISS will pass over your town, using either Heavens Above (just enter your city and click the ISS link on the homepage), Spaceweather’s Flyby page or NASA’s Spot The Station site, look in the west for a bright, moving “star” that gradually grows brighter as it gets closer.

The space station always moves to the east in the opposite direction of the stars. On Heavens Above, you can view the actual path of the ISS by clicking the date link in the visible passes column. When it crosses near the overhead point, it’s only about 250 miles from you and absolutely brilliant. But when you first see the space station low in the western sky, it’s looks fainter because it’s about three times farther away. That’s because of all the horizontal distance between you and the craft.

There’s another factor in the changing brightness of the ISS — phase. Like the moon it goes through phases as the angle between the station, the observer and the sun changes. When you first see it low in the west, the station’s edge is illuminated by the sun the same way a crescent moon is. As the ISS ascends, more of more of it gets lit by the sun. By the time it’s due south, it’s roughly in half-moon phase. And when it moves into the eastern sky, a waxing gibbous. The more it fills out, the brighter it gets … to a point. When low in the eastern sky and nearly “full,” it’s also quite far away and fading. That makes the station brightest when it’s in the eastern sky but not directly overhead. Take a look yourself on the next pass and see if you can tell where it appears brightest.

The ISS and an airplane (red and green trail) cross the same part of the sky in this time exposure photo taken last spring. If you look closely at the space station trail, you can see how it fades and reddens (at left) as it’s eclipsed by Earth’s shadow. Credit: Bob King

On some nights, the ISS will make up to four passes — a couple in the early morning hours and a couple in the evening. As you follow the moving light with your eyes, it’s fun to realize that the current Expedition 52 crew on board has been busy wrapping up an intensive week of research on learning how to lessen the effects of long-duration spaceflight on the human body. One more study in a never-ending battle on keeping people fit in the zero-G environment of space.

This nighttime photo of Florida was taken back in March. Bright lights of cities stand out, including the Miami-Fort Lauderdale metropolitan area, the Tampa Bay region along the Gulf Coast, and in the middle, Orlando. At upper left, green airglow is seen; at right, the beginning of morning twilight somewhere over the Atlantic Ocean. Credit: NASA

You and I, who are bound to Earth, may not like the long-term effects of gravity dragging us down, but without it, bones weaken, making astronauts more susceptible to falls and broken bones . Muscles also lose mass. Even with 2 hours of exercise a day, after a typical 6-month mission, astronauts still need months back on Earth for their bodies to return to normal. Increased radiation exposure may also increase a crew member’s chances of getting cancer.

There are even more hazards, all of which the astronauts are made aware in their training, but the allure of space and the opportunity to do important research 250 miles high keep ’em coming back. To prove the point, three new crew members will launch to the station on July 28 aboard the Russian Soyuz MS-05 spacecraft.