|
TIMED Overview
For centuries, scientists have realized that Earth's natural environment is greatly impacted by the abundance of solar energy striking the Earth from a constantly changing sun. Over the last few years, they have begun to realize that human activities are also playing a role in changing our environment.
By studying portions of Earth's atmosphere, scientists believe global change is occurring, primarily due to variations in the sun's cycle and from human-induced changes to the atmosphere by the release of gases, such as methane and carbon dioxide. Despite signs of global change, scientists haven't had a benchmark against which future changes in Earth's upper atmosphere can be globally compared, analyzed, or predicted because there are still portions of this solar-terrestrial chain, including regions within Earth's atmosphere, that are poorly understood.
The 2-year TIMED (Thermosphere • Ionosphere • Mesosphere • Energetics and Dynamics) mission is studying the influences of the sun and humans on the least explored and understood region of Earth's atmosphere – the Mesosphere and Lower Thermosphere/Ionosphere (MLTI). The MLTI region is a gateway between Earth's environment and space, where the sun's energy is first deposited into Earth's environment. TIMED is focusing on a portion of this atmospheric region located approximately 40-110 miles (60-180 kilometers) above the surface.
 |
| Noctilucent clouds, as the name implies, are clouds that shine at night. They are found at higher altitudes (approximately 50 miles, or 82 kilometers) than most clouds (9 miles, or 15 kilometers). Photo courtesy of Oscar van der Velde. Do not use or reproduce without permission of the photographer. Click image for enlarged view. |
In a society increasingly dependent upon satellite technology and communications, it is vital to understand the variability within this critical region of our atmosphere, so scientists can predict its effects on communications, satellite tracking, spacecraft lifetimes, degradation of spacecraft materials, and on the reentry of piloted vehicles. TIMED's study of space weather will help scientists gain a better understanding of the dynamics of this gateway region.
A comprehensive global study of the MLTI region has never before been accomplished. Ground-based instruments can only observe a small portion of the upper atmosphere located over an observation site. This region is too high for balloons to reach. Sounding rockets (rockets that fly into the upper atmosphere for just a few minutes before falling back down) can only provide a brief snapshot of the MLTI region's activity near the rocket. Other spacecraft have studied portions of the MLTI region, but TIMED will be the first mission to obtain a global picture of it, which scientists need to better understand our upper atmosphere. The TIMED mission will establish a baseline against which future studies of changes within this region can be compared and analyzed.
The TIMED spacecraft is observing this relatively unexplored frontier from its 388-mile (625-kilometer), circular orbit around the Earth. Employing advances in remote-sensing technology, the spacecraft's instrument suite is working with a worldwide network of ground-based observation sites to obtain an unprecedented set of comprehensive global measurements of the region's temperature, pressure, winds, and chemical composition, along with its energy inputs and outputs.
The TIMED spacecraft is the initial mission in NASA's Solar Terrestrial Probes Program, part of NASA's initiative to lower mission costs and provide more frequent access to space to systematically study the system. TIMED was launched aboard a Delta II launch vehicle on Dec. 7, 2001 from Vandenberg Air Force Base, Calif.
The TIMED mission is sponsored by the National Aeronautics and Space Administration's (NASA) Office of Space Science, Washington, D.C., and is managed by NASA's Goddard Space Flight Center, Greenbelt, Md. The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., designed, built and is operating the spacecraft and leading the project's science effort for NASA during the mission.
|
