ICESat's sole instrument -- the Geoscience Laser Altimeter System (GLAS). Photo: NASA

The Geoscience Laser Altimeter System instrument for NASA's Ice, Cloud, and Land Elevation Satellite (ICESat), has arrived at Ball Aerospace in Boulder, Colo., for integration with the spacecraft.

The instrument left NASA's Goddard Space Flight Center, Greenbelt, Md., June 13 on its journey to Colorado. ICESat will use lasers that were designed and built by Goddard.

The benchmark Earth Observing System mission will achieve Earth Science Enterprise requirements for measuring ice sheet mass balance, cloud and aerosol heights, vegetation structure and land topography.

ICESat will provide scientists with vital information about cloud properties, which are not otherwise available from passive sensors, especially high ice clouds that are common over polar areas. ICESat will collect data to correlate the rise or fall of the world's sea level to the respective loss or accumulation of the ice volume covering Antarctica and Greenland.

An artist's concept of ICESat in orbit. Photo: NASA

The mission will attempt to answer such puzzling questions as:

• Are the Greenland and Antarctic ice sheets growing or shrinking?
• What are the ice sheets' contributions to sea level rise?
• Can ice sheets cause large, rapid changes in sea level?
• Will the ice sheets melt or grow in a warmer climate?

GLAS, the first laser-ranging instrument for continuous global observations of Earth, will make unique observations as an important component of the Earth Science Enterprise climate change program.

ICESat is scheduled to launch this December aboard a Delta 2 rocket from Vandenberg Air Force Base, Calif.