A special window designed to constantly face the Earth will enable a wealth of research projects, said Dr. Dean Eppler of the ISS Payloads Office. The window, at 20 inches across, is the biggest ever designed for a spacecraft. It is made of special glass which, unlike common glass, will not distort, degrade or refract light that passes through it. In effect, it will be as if there is no window between the Earth and the sensitive telescopes and cameras.

Observations from the ISS will help scientists monitor, among other things, plate tectonics, fish populations, the effects of pollution, overpopulation and global warming, as well as the health of coral reefs. Dr. Marco Noordeloos, of the International Center for Living Aquatic Resource Management in the Philippines, said coral reef degradation, which could adversely affect the lives of millions of people living in the tropics, can only be effectively studied from space.

At a time when planetary scientists are keen to land spacecraft on other planets, it may seem ironic that geologists want to position a spacecraft above our own planet to study it. But distance has its advantages, like the ability to see Earth in very great detail.

So far, this hasn't been possible. "We have better images of Mars than of the Earth," said Dr. William Muehlberger of the Department of Geologic Science at the University of Texas at Austin. Indeed, the resolution of cameras aboard the Mars Global Surveyor is 1.5 meters, many times better than the cameras on Earth-imaging satellites currently in space.

"What you want," added Dr. Eppler, "is a host of scales to look at." The ISS, along with other remote sensing satellites already in existence, such as Landsat 7, as well as high-altitude aircraft, will provide a suite of observations to help scientists understand planet Earth as never before.