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| solar eclipse-PhysicsKnow |
While millions of
Americans gather across the country to catch a glimpse of Monday's total solar
eclipse, the astronauts aboard the International Space Station will view the
event from a much different vantage point.
The ISS crew members
are predicted to view both a partial eclipse and the moon's shadow cast on the
North American continent as they make three tracks around the planet 400 km
above Earth's surface, according to NASA.
"Observing a
total solar eclipse from manned spacecraft is difficult though not
impossible," NASA reported.
NASA said the
different rates of speed and intersecting paths are the main challenge to
viewing an eclipse from space.
At minimum, ISS
spends less than 15 seconds traversing the 100-km-wide lunar shadow even when
the paths align in space and time, according to NASA. However, Earth’s horizon
extends nearly 2,300 km from the ISS, allowing astronauts to see the lunar
shadow if they are close enough during the event.
The total eclipse
will begin on the Oregon coast at 17:15 UT (10:15 a.m. PDT) and will end along
the South Carolina coast at 18:49 UT (2:49 p.m. EDT).
As the space station
makes its first pass during the eclipse, the crew members will be able to view
a partial solar eclipse with approximately 37 percent of the sun covered up,
NASA reports.
However, at this
point in time, the ISS will not be able to see the umbra, or the darkest part
of the moon's shadow on the Earth's surface. The space station will pass over
the western United States and southeastern Canada in the first pass. The total
portion of the eclipse will not have started yet for the Earth.
As the station makes
its second pass through the moon's shadow, the partial eclipse will be visible
to the astronauts with 44 percent of the sun covered.
"ISS will
witness the moon’s umbra moving from southwestern Kentucky to northern
Tennessee during a portion of this pass," NASA reports.
"The moon’s
umbra is visible on the Earth from ISS’s viewpoint while ISS traverses from
southern Canada just north of the Montana-Canada border to the Gulf of Saint
Lawrence."
At its closest
approach, the space station will be making its way south of the Hudson Bay, far
removed from the moon's umbra, which will be passing over southwestern Kentucky
nearly 1,700 km away.
However, despite the
distance, crew members aboard the ISS should still be able to view the shadow
near the horizon.
The third pass for
the ISS will bring another view of a partial solar eclipse with 85 percent
coverage just minutes before orbital sunset. At this point, the darkest part of
the lunar shadow will no longer be visible to crew as the umbra will have
lifted from the Earth's surface as it makes its transit.
"Because of
atmospheric friction and other ISS activities, the orbits undergo small changes
from week to week," NASA reports.
The most precise
timing will be available on NASA's ISS observations website.
