How ISS astronauts will see the eclipse

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The moon’s shadow on Earth, seen on August 11, 1999 from the Russian Mir space station. Those in the shadow’s path – the path of totality – see a total solar eclipse. Outside the shadow, you might see a partial solar eclipse. Image via Mir 27 Crew/ CNES. This shadow moves across the Earth at some 1,200 miles per hour (nearly 2,000 km per hour). Will the astronauts aboard ISS see it and capture an image on Monday, August 21?

U.S. roads will be crowded on Monday with travelers to the path of totality of the August 21, 2017 solar eclipse. But no one has traveled farther than the astronauts aboard the International Space Station (ISS). Will they see a total eclipse from space? No. According to NASA’s EclipseScience, during this eclipse, ISS will pass through the moon’s penumbral shadow – its lighter, outer shadow – three times. It won’t ever pass through the darker, inner portion of the moon’s shadow – called the umbra. Thus ISS astronauts won’t see a total solar eclipse. Instead, they’ll see a partial eclipse from their vantage point in space. However, during ISS’s second pass through the moon’s penumbral show, the astronauts might be able to see and perhaps capture images of the moon’s shadow on Earth, from the perspective of space, assuming their view isn’t blocked by ISS itself. Plus, from some places during pass #1, people will see a transit of ISS across the face of the sun. Follow the links below to get more details.

ISS penumbral pass #1

ISS penumbral pass #2

ISS penumbral pass #3

ISS pass #1. A partial eclipse is already in progress and is witnessed by ISS. Image via NASA.

Event times for pass #1, via NASA.

ISS penumbral pass #1. During its first pass through the moon’s penumbra shadow, ISS will experience a partial solar eclipse with 38.0% of the sun covered up at maximum. ISS will not see the moon’s umbra on the Earth’s surface during this pass, or any of the three passes it makes through the moon’s shadow. In pass #1, ISS passes over the western United States and southeastern Canada. At the time of the figure (16:40:33 GMT), the total portion of the eclipse has not yet started for the Earth.

During pass #1, an ISS transit of the sun will occur. In other words, ISS will appear to cross in front of the sun’s face, as seen from a very thin ground track from California through Canada. There’s only one place where you could witness both a transit of the ISS across the partially eclipsed sun and the total solar eclipse later in the morning; it’s at the intersection of this transit path with the moon’s shadow path in Wyoming. The community of photographers that takes photographs of transits no doubt already knows about these events, since they’re mentioned on two popular online calculators, which provide exact times: https://www.calsky.com and http://transit-finder.com. The rest of us can look forward to the photos!

ISS pass #2. Image via NASA.

During pass #2, the moon’s park umbral shadow will be visible to astronauts aboard ISS. This illustration shows ISS at the mid-point of the eclipse – during this pass – from the perspective of the sun and from a perspective of ISS itself, looking ISS-starboard. Image via NASA.

Event times for pass #2, via NASA.

ISS penumbral pass #2. On the second pass of ISS through the moon’s penumbral shadow, those aboard will again experience a partial solar eclipse. This time, at maximum eclipse, 43.9% of the sun is covered. Also, during this pass, the moon’s dark central umbra – the part of the shadow that causes the total eclipse (seen in the image at the top of this page) – will be visible from ISS moving through southern Illinois and southwestern Kentucky. At the time, ISS itself will be traversing over southern Canada. At the umbra’s closest approach to ISS, the space station will be just south of the Hudson Bay while the moon’s umbral shadow is located in southwestern Kentucky some 1,200 miles (1700 km) away. While ISS does not pass near the location of the moon’s umbra, the moon’s umbra will be easily visible near the horizon, assuming the view of it from ISS is not blocked by some portion of the space station itself. No doubt the astronauts know this and are ready to capture images!

While an ISS transit of the sun will occur over a very thin ground track from Washington through Canada, there is not a single location on land where one can witness an ISS transit during this pass and the total solar eclipse. This intersection occurs over the Pacific Ocean.

ISS pass #3. This pass provides the deepest partial eclipse as seen from ISS. Image via NASA.

Event times for pass #3, via NASA.

ISS penumbral pass #3. During its third pass through the moon’s penumbral shadow, ISS will experience a partial solar eclipse with 84% of the sun covered up at the maximum point a few minutes prior to orbital sunset. ISS will not see the moon’s umbra on the Earth surface during this pass, since the umbra will have just lifted off the Earth’s surface a few minutes prior to the start of ISS’s eclipse on this pass. However, this pass offers the opportunity to see the sun partially eclipsed as it sets into the atmosphere with 26.7% of the sun covered by the moon (assuming no structural blockage by ISS itself). The figure below represents ISS’s location at maximum eclipse, which occurs a few minutes prior to sunset, as viewed from the sun.

While an ISS transit of the sun will occur over a very thin ground track across Canada during this pass, there is not a single location on land where one can witness an ISS transit during this pass and the total solar eclipse. This intersection occurs over the Pacific Ocean.

The solar eclipse of March 20, 2015, as captured from aboard the International Space Station by astronaut Samantha Cristoforetti. Check out her series of 21 photos of that eclipse.

Bottom line: A page of information – based on info at NASA’s EclipseScience – that describes three passes of the International Space Station through the moon’s penumbral shadow during the August 21, 2017 total solar eclipse.

Deborah Byrd

Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.


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