At almost literally the last minute, NASA launched five suborbital sounding rockets early Tuesday on a mission to study high-level jet stream winds by creating artificial glowing clouds near the edge of space.
After several delays, the rockets started blasting off from their pads in Virginia just before the close of the day's scheduled launch window at 5 a.m. ET. The launches were held up until the very end by concerns about winds as well as boats that had strayed into the restricted range zone. But all the conditions turned "green" just in time for liftoff.
Each of the five unmanned rockets released a chemical tracer into the jet stream winds more than 60 miles up, creating milky white trails in the nighttime sky. Observers along the U.S. East Coast, from Massachusetts to North Carolina, reported seeing the high-altitude streaks at the edge of space, NASA said.
The mission, which is called the Anomalous Transport Rocket Experiment, or ATREX for short, had been on hold since the night of the first launch attempt on March 15.
That night, radio frequency interference on one of the five rockets precluded a launch. Since then, unfavorable weather has been the main problem.
The rockets were launched from NASA's Wallops Flight Facility, which is located along the Mid-Atlantic coastline at Wallops Island, Va. [Photos: NASA's ATREX Rocket Barrage Mission]
In addition to the launch site, NASA set up cameras to photograph the rockets' luminous vapor trails from two other locations: the Rutgers Marine Field Station in Tuckerton, N.J., and the U.S. Army Corps of Engineers at Duck, N.C. Clear skies at all three locations were essential for the mission to go forward.
Each rocket ejected a chemical tracer called trimethyl aluminum (TMA), which was illuminated at high altitudes by the sun, even though it was below the local horizon at ground level.
Trimethyl aluminum is an organometallic compound that is liquid at room temperature. Though nontoxic, TMA is dangerous because it can ignite spontaneously.
In rockets, the chemical is kept under pressure. At the very low pressures of the Earth’s upper atmosphere, some of the released TMA evaporates, but the rest freezes into solid particles. At an altitude of roughly 62 miles (100 kilometers), heating by friction causes further evaporation, and the particles shine in part by a chemiluminous process.
In several cases, scientists expected bluish-white clouds to be created, resulting from the chemical reaction of TMA with atomic oxygen in the atmosphere to produce molecules of aluminum oxide. At the high altitude where the TMA is released, the molecules are directly illuminated by sunlight, which excites them and causes them to glow.
What do we learn?
Using time-lapse photography from the New Jersey and North Carolina sites, the drift of the cloud trails can be accurately determined, indicating the direction and speed of the winds at these high altitudes.
Such winds continually transfer heat and matter from the Earth’s sunlit hemisphere around to its dark side. In addition, the rate of diffusion of the trails will give scientists an idea of how fast the TMA that was deposited will disappear.
The rate of diffusion is inversely proportional to the density of the air which decreases in height. With this in mind, the cloud trails and puffs that are released at higher altitudes will likely appear wider and larger, and should expand much faster than those trails that are released at lower altitudes.
If you snap an amazing photo of the glowing clouds released by NASA's ATREX rockets, or any other sky object, and would like to share them with Space.com for a story or gallery, please contact managing editor Tariq Malik at: firstname.lastname@example.org.
This report was updated by msnbc.com. Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y.