16 septembre 2009 3 16 /09 /septembre /2009 23:57
MNBC
Sept 16 2009

Experiment plans to simulate noctilucent clouds, which are sky’s highest
By Clara Moskowitz


This image shows sightings of noctilucent clouds over Budapest, Hungary on June 15, 2007.

A rocket experiment aims to create artificial clouds at the outermost layers of Earth's atmosphere.


The project, called the Charged Aerosol Release Experiment (CARE), plans to trigger cloud formation around the rocket's exhaust particles. The clouds are intended to simulate naturally occurring phenomena called noctilucent clouds, which are the highest clouds in the atmosphere.


"This is really essentially at the boundary of space," said Wayne Scales, a scientist at Virginia Tech who will use computer models to study the physics of the artificial dust cloud as it's released. "Nothing like this has been done before and that's why everybody's really excited about it."


The experiment is the first attempt to create artificial noctilucent clouds. A previous spacecraft, called Aeronomy of Ice in the Mesosphere (AIM), launched in 2007 to observe the natural clouds from space.


CARE was initially slated to launch atop a suborbital research rocket on Tuesday evening from NASA's Wallops Flight Facility in Virginia, but cloudy weather at liftoff time forced a postponement until Friday at the earliest.


Noctilucent means "night shining" in Latin. Although difficult to spot with the naked eye, the clouds are best visible when Earth's surface is in darkness and sunlight from below the horizon illuminates the high-altitude clouds.


These clouds, also known as polar mesospheric clouds, are made of ice crystals. The natural ones tend to hover around 50 to 55 miles (80 to 90 km) above the Earth. CARE will release its dust particles a bit higher than that, then let them settle back down to a lower altitude.


"What the CARE experiment hopes to do is to create an artificial dust layer," Scales told Space.com. "Hopefully it's a creation in a controlled sense, which will allow scientists to study different aspects of it, the turbulence generated on the inside, the distribution of dust particles and such."


CARE is a project of the Naval Research Laboratory and the Department of Defense Space Test Program. The spacecraft is due to launch aboard a NASA four-stage Black Brant XII suborbital sounding rocket.


Scientists will study its progress from ground-based instruments as well as the STP/NRL STPSat-1 spacecraft in Earth orbit. Researchers will track the CARE dust cloud for days or even months to study its behavior and development over time.


Because the optical observations are crucial, the launch can only take place if the weather is clear both at the launch site and at multiple observation stations along the Atlantic coast and in Bermuda. Based on weather forecasts, NASA said Friday was the next opportunity for launch.

This report was updated by msnbc.com.


© 2009 Space.com. All rights reserved. More from Space.com

URL: http://www.msnbc.msn.com/id/32845270/ns/technology_and_science-space/

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