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The Gateway to Astronaut Photography of Earth

(NASA Crew Earth Observations)

"We catch a glimpse of a huge swirl of clouds out the window over the middle of the Pacific Ocean, or the boot of Italy jutting down into the Mediterranean, or the brilliant blue coral reefs of the Caribbean strutting their beauty before the stars. And...we experienced those uniquely human qualities: awe, curiosity, wonder, joy, amazement." (Russell L. Schweickart, Apollo Astronaut ("The Home Planet")

Photographing the Earth from the International Space Station

A Window on the Earth:
Earth Sciences from the International Space Station and
The Window Observational Research Facility (WORF): Optical-Quality Window


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Optical-Quality Window:

In the summer of 1994 NASA approved adding an optical-quality nadir-viewing window to the U.S. Laboratory Module of the International Space Station. The window can view 39.5 degrees forward along the axis of the ISS, 32.2 degrees aft, and a total of 79.1 degrees from port to starboard.

Japanese Experiment ModuleIllustration Illustration Illustration

Schematics of the International Space Station, showing the field of view for the window in the x-z and y-z plane.

The window is constructed of three panes of fused silica and a fourth protective kick pane made of glass laminate. From outboard to inboard, the panes are shown here.

The kick pane is removed during window research operations to take advantage of the full spectrum of radiation that passes through the fused silica panes. 1998 drawing of the window and external shutter.


  • An external debris pane that can be changed by an EVA astronaut if damaged.
  • A redundant pressure pane.
  • A primary pressure pane.
  • A scratch or "kick" pane that:
    • protects the primary pressure pane from being damaged if the crew or equipment make contact with the window
    • provides a UV-IR coating to protect the crew members


When not in use, the window is protected by the kick pane on the inside, and by an external cover on the outside. The external cover can be rotated in or out of position from within the cabin by an astronaut using a hand crank.

The Research Management Office at Johnson Space Center has conducted numerous interferometric and visual tests to establish the transmission properties of the window. Details of these tests can be found in the references.

For remote sensing purposes, the spectral properties of the window are most important. As seen in the graph below, the reflective coating on the window absorbs UV radiation, but transmittance rises rapidly after 304 nm to > 90% in the visible and into the near infrared. Transmittance tails off after 800 nm, reaching zero at approximately 2600 nm.

Transmittance of Flight Article Window Panes