About Human Spaceflight

International Space Station
Space Station in April 2002
The International Space Station in April 2002

Crewmembers looking through window
Space Station crew members look out the optical quality window of the ISS.

The NASA tradition of Earth observation from human-tended spacecraft continues on the International Space Station (ISS) with new opportunities for high-quality spatial and spectral resolution. Part of the station, the U.S. Laboratory Destiny, has a special Earth observing window with a clear diameter of 50.8 cm. The window is constructed of fused silica polished to telescope-quality optical characteristics. The reflective coating on the window absorbs UV radiation, but transmittance rises rapidly after 304 nm to > 90 percent in the visible and into the near infrared. Transmittance begins to tail off after 800 nm, but is nearly 50 percent to 1,500 nm. It is effectively zero at approximately 2,600 nm (see window transmittance graph).

Photographic cameras including film cameras, digital still cameras, and IMAX have all used the lab window for Earth imaging. This window permits the use of remote sensing instruments inside of the spacecraft without the need for space hardening, allows for instrument configuration changes while on orbit, and the return of instruments to the ground for servicing or calibration. Such instruments will be mounted in the Window Observational Research Facility (WORF) which provides a place for sensor mounting as well as vibration isolation, power and data transfer capabilities in the window. The WORF is scheduled for installation in the window in 2003. Several remote sensing instruments are being considered for deployment in the window; remote sensing instruments can also be mounted on external Station platforms.

Mission Facts
The International Space Station began construction in November 1998, and Earth Science activities began with the arrival of the first crew members in October 2000. At approximately 200 nautical miles (400 km) in altitude, the orbital inclination of the Station is 51.6 degrees and covers over 75 percent of Earth’s surface, containing 95 percent of human-inhabited areas. Orbits take approximately 91 to 93 minutes with a repeat about every 3 days and a 63-day lighting cycle.

Orbital characteristics of the ISS

Current position of the ISS in orbit

Window Observational Research Facility (WORF)

Earth Science Projects on the Station
Destiny windowISS Crew member Sergei Krikalev looks out the optical quality window in the Destiny U.S. Laboratory.

Crew Earth Observations (CEO) is the project guiding astronaut handheld photography from the ISS. Crew Earth Observations focuses on some of the most dramatic examples of change on the Earth’s surface. An interdisciplinary group of scientists selected some of the most dynamic regions of the Earth as their initial target sites (PDF format) that could be observed under the tight time constraints of the early phases of Space Station construction. These sites include major deltas in south and east Asia, coral reefs, major cities, smog over industrial regions, areas that typically experience floods or droughts triggered by El Niño cycles, alpine glaciers, tectonic structures, and features on Earth, such as impact craters, that are analogs to structures on other planets.

Fires in Indonesia
Fires in Indonesia as photographed by EarthKAM students

EarthKam installation
Astronaut Bonnie Dunbar installs the EarthKAM digital camera in the Orbiter window.

Earth Knowledge Acquired by Middle school students (EarthKAM) is a project where middle school students control a digital camera mounted in the window of the ISS. It began in 1994 as a pilot program on the Space Shuttle (then known as “Kidsat”) and is now a long-term program on the Space Station. Students request that specific images of Earth be taken from orbit and the images are then incorporated into their classroom curricula. These photos are used to study the planet from a variety of disciplines, geography to environmental studies to visual arts. The images will soon be included in the larger Gateway to Astronaut Photography of Earth, to extend their availability to the public and scientific community.

Stratospheric Aerosol and Gas Experiment (SAGE III) is the first U.S. Earth observing project planned for external mounting. The SAGE III instrument characterizes the vertical distribution of aerosols and ozone from the upper troposphere through the stratosphere. In addition, SAGE III also provides unique measurements of temperature in the stratosphere and mesosphere and profiles of trace gases such as water vapor and nitrogen dioxide that play significant roles in atmospheric radiative and chemical processes. It is scheduled to go into orbit in 2004.

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About Human Spaceflight
International Space Station
Space Shuttle
Astronaut Photography

Pinaki Atoll
Tiny Pinaki Atoll in the Tuamotu Archipelago, French Polynesia, was photographed from the Space Station as part of the CEO project to obtain images for coral reef mapping applications.

This photograph shows a sunrise over Pecos, Texas, as photographed from the space shuttle. Clouds (blue-white) and the stratospheric aerosol layer (red) are clearly visible in this image. SAGE III measures the obscuration of the sun by the Earth’s atmosphere from a geometry similar to that in this image.