| Volume 4, | Number 1 | March/April 1996 |
When the U.S. Laboratory Module attaches to the International Space Station in November 1998, scientists and engineers will have a new, unique view of the world. The U.S. Lab will be equipped with a high-quality Earth-viewing window that will provide scientists, engineers and others with opportunities to study the Earth and to develop more powerful sensors for observing the Earth as never before.
The Space Station will orbit approximately 218 to 250 miles above the Earth's surface, and its path will range from 51.6 degrees north to 51.6 degrees south. At this orbital inclination, more than 75 percent of the Earth's land and sea surfaces will be available for observation from the window. The Space Station will offer one of the first long-term and best window research facilities because the U.S. Lab will regularly orbit over the same spot for more than 10 years. In addition, full Space Station utilities, such as thermal, power, nitrogen and data, will be available for special sensors to be used with the window. Images from space have many applications; they can be used to study global climates, land and sea formations, and map routes for city planners. Special sensors can also provide important data-for example, atmospheric conditions or properties as well as data for new sensor technology development.
The window will be the largest ever available for observation, engineering and scientific study from a spacecraft. It will have 20 inches of a clear, direct viewing area. The window will consist of three fused panes and is designed to allow rays from mid-ultraviolet through reflected solar infrared to be transmitted through the window. There will also be one removable pane that carries an ultraviolet blocking coating to protect the astronauts from harmful rays while using the window for general viewing. This pane will also serve to protect the primary panes from damage.
One of the most important characteristics of the window is the wave front error, or the amount of distortion caused by the glass. This distortion must be controlled; otherwise, it will cause images to be blurred or data to be degraded. While images through the glass might not appear distorted to the human eye, wave front error becomes critical when using large aperture instruments such as cameras or telescopes. They sample more of the wave front than the human eye and, therefore, are more sensitive to error. The result can be degraded images or data. Activity is under way to procure a window that will allow up to 8-inch aperture instruments to be used without serious image distortion.
The window has already generated interest among several programs. One experiment proposes to use the window to study lightning bolts from space, and another program, KIDSAT, proposes to download images of the Earth from a digital camera into elementary and high schools. Individuals are invited to contact the people listed below if interested in using the window or to obtain more information. Progress reports to potential Space Station users are posted regularly on the World Wide Web at http://issa-www.jsc.nasa.gov/
The equal area map projection, with shaded portion showing the Earth's surface between 51.6š north and south latitude, will provide direct nadir viewing (downward at the Earth) for more than 75 percent of the Earth's surface.
For more information, contact Dean Eppler at the Johnson Space Center. Phone: 713/244-8216, E-Mail: deppler@ssf4.jsc.nasa.gov Or contact Joe Sullivan at the Johnson Space Center. Phone: 713/244-7877, E-Mail: jsulliva@ssf4.jsc.nasa.gov Please mention that you read about it in Innovation.
