London, September 22 (ANI): With the help of a rocket, scientists have created an artificial cloud at the edge of space, to learn how high-flying dust reflects radio waves.
"Noctilucent", or night-shining, clouds float dozens of kilometres higher than other clouds, at an altitude of about 80 kilometres.
Because of their height, they can be seen glowing before sunrise or after sunset as the sun illuminates them from below the horizon.
In recent years, they have spread to latitudes as low as 40degrees, while also growing in number and getting brighter - a change that some attribute to global warming.
The ice-covered particles in these clouds are commonly thought to get their start as tiny dust particles that had been sloughed off comets and meteoroids.
These particles build up a charge as they are bombarded by fast-moving electrons and ions.
Since charged particles reflect radio waves, they are good candidates for radar studies, which could help measure the dust at an early stage in the clouds' formation.
But the radar data is hard to interpret.
To get a better sense of how high-flying dust reflects radio waves, researchers launched the Charged Aerosol Release Experiment (CARE) recently from NASA's Wallops Flight Facility in Virginia, US.
The experiment, which blasted off on a Black Brant XII suborbital sounding rocket, spewed more than 100 kilograms of aluminium oxide into the atmosphere at an altitude of about 280 km.
A combination of ground- and space-based instruments will watch this cloud for days and perhaps months as its particles become charged, sink, and disperse.
Laser pulses will be used to measure the density of the particles in the cloud. These will be compared with radar measurements of the plume.
"Our primary science goal is to understand (how) radar (scatters) from a dusty plasma," said CARE's principal investigator, Paul Bernhardt of the Naval Research Laboratory in Washington, DC.
"We want to understand what kind of information you get back when you send out radar pulses," he added.
Radar has been used to examine icy dust that hovers some 90 km above the Earth and can grow to become the ice particles inside noctilucent clouds, according to Scott Bailey of Virginia Tech in Blacksburg.
But at the moment, interpreting radar measurements of these proto-cloud particles is difficult.
Studying an artificial cloud created in a controlled manner could help resolve these uncertainties.
"If the radar could be used to say exactly what the population of particles is up there that the ice is forming around, that would be a major step forward," Bailey told New Scientist. (ANI)