Satellite to Study Auroras Ready for Launch

Satellite to Study Auroras Ready for Launch
An artist's concept of the THEMIS spacecraft in orbit.
(Image: © NASA.)

Five NASA probesaimed at unraveling mysteries surrounding Earth's colorful auroras are set to launch Fridayevening after a 24-hour weather delay.

VIDEO:Aurora - Dangerous Beauty

A United LaunchAlliance Delta 2 rocket carrying the fiveprobes that make up the Time History of Events and Macroscale InteractionsDuring Substorms (THEMIS)mission is scheduled to liftoff between 6:05 and 6:23 p.m. EST on Feb. 16 fromPad 17-B at Kennedy Space Center (KSC) in Florida. The launch will set a newNASA record for the most number of scientific satellites ever launched intoorbit aboard a single rocket. [VIDEO: THEMIS launch animation.]

"We'recomplete through all of our readiness reviews," KSC launch director Chuck Dovaletold reporters Thursday during a press conference. "The team is poised to startcountdown tomorrow and we're ready to go."

The probeswere originally set to launch on Thursday, Feb. 15, but thunderstorms and severeweather in the Cape Canaveral region the day before interrupted fueling of the rocket.

Weatherforecasters are optimistic that winds tonight will not reach beyond about 29mph (25 knots), which is the minimum requirement for a launch abort.

"I am lookingat a 20 percent 'no go' for tomorrow's launch based on wind," said Air Force weatherofficer Joel Tumbiolo. "That's 80 percent 'go.' That's a pretty good chanceright there."

THEMISconsists of five identical probes [image],each about the size of a dishwasher and weighing nearly 300 pounds, that willspread out to form a unique constellation aimed at studying the auroraborealis and auroraaustralis--the colorful light shows that occur over Earth's northern andsouthern polar regions, respectively.

Undulatinglike rainbow ribbons in the sky, auroras are visible manifestations ofso-called "geomagnetic substorms" that occur in near-Earth space. These substormsare caused when electrically charged gas blown by the Sun's solar winds slam against Earth's magnetic shied, called the magnetosphere.

THEMIS willhelp answer scientific questions about when and where the substorms start, butit could also have practical implications, said Dick Fisher, director of NASA'sHelios Division. For example, Fisher said, airlines currently require pilotsflying over the North Pole to maintain constant communications. Ifcommunications is broken, as can occur during substorms, pilots are required toland their planes. Being able to predict when substorms might occur could thushelp airlines better plan their routes. [VIDEO: THEMIS mission overview.]

"To get ajetliner on the ground and make it stay overnight costs a lot of money," Fishersaid.

When theybegin data collection next winter, the five THEMIS probes [image]will align over North America once every four days [image],allowing 20 ground stations in Canada and Alaska to monitor substorms for 15 to20 hours at a stretch. Over the mission's two-year lifetime, the probes areexpected to observe some 30 substorms.

"We'relooking forward to the next challenge," aid UC Berkley's Peter Harvey, NASA'sTHEMIS project manager, "which is synchronizing all five spacecraft over NorthAmerica and keeping them humming along."

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