Sunday, December 26, 1999

High-flying science

Published in the Antarctic Sun

In the next few days, a giant floating bubble will appear over Williams Field and climb high into the heavens. It will circle Antarctica for about two weeks, and return to Earth nearby.

The bubble is a helium-filled balloon 100 feet tall. It will carry a scientific payload almost 24 miles into the sky, from which altitude it will still be visible to the unaided eye.

The Flare Genesis Experiment, as the project is called, is looking at the origin of solar flares to determine what causes them. What is known at present is that flares emerge from sunspots in which the magnetic field changes, becomes unstable and erupts in a flare.

“We want to know how flares are born,” said David Rust of Johns Hopkins University’s Applied Physics Laboratory, the lead scientist on the project.

Using the 32-inch solar telescope, the second-largest in the world, Rust and his team can look at sunspots very closely.

By measuring the polarization and shifting wavelength of the light emitted from a specific sunspot, Rust and his team can calculate the magnetic field acting on the area.

He and others have spent 25 years trying to put together a space mission to do this work. It would cost $800 million, though it would yield years of observing opportunities from a space vehicle.

The balloon launch, on the other hand, costs $16 million for about two weeks of observing the sun. The last time the telescope went aloft, in 1997, it stayed up for 18 days.

The scientists are supported by the NASA-funded National Scientific Balloon Facility, based in Palestine, Texas. The facility takes care of elements of the project apart from the telescope and its housing.

“We provide the vehicle, we provide the telemetry system,” said Steven Peterzen, the NSBF’s on-site coordinator. The facility’s staff also rigs the balloon, performs the launch, monitors the flight, and pops the balloon to end the flight. But even then, the job isn’t done. The payload’s valuable instrumentation must be recovered.

“We do this all over the world,” Peterzen said. Antarctica is a good place to send up balloons because of the emptiness of the space, but more importantly because of the regular wind pattern
which stabilizes over the continent in midsummer. The balloon, when launched from Williams Field, will circle the continent and most likely return nearby, to be brought down on the Ross Ice Shelf for easy recovery.

During the first 20 hours of the balloon’s flight, the scientists can communicate extensively with the payload because it is within line-of-sight. They run tests to be sure everything is working
properly, and collect some early data. All data is stored on board for the duration of the flight.

After those first hours, though, the balloon and its payload are only reachable for a few minutes every couple of hours. If something goes wrong, the scientists can load all of their equipment into
the back of an LC-130 and fly closer to the payload, to regain line-of-sight communications.

The NSBF team at Williams Field has enough equipment to have the two balloons in the air at once, though that has never happened before in Antarctica.

They can only have one at a time in line-of-sight, though, meaning a second launch can follow the first only after a day or two.

Later this season a similar launch will lift a project run by a research team led by scientists at the University of California-Berkeley and the University of Washington, who didn’t even expect
to launch their project in Antarctica this season.

They had hoped to launch in Alaska last June, but were unable to. Then, in August, they got a phone call: Another group wasn’t ready to come to Antarctica.

They scrambled to make the trip, helped by the fact that they’d never really unpacked in June.

“It was all still in boxes,” said Robyn Millan, a graduate student at UC Berkeley’s Space
Sciences Laboratory.

The instruments will show them more about aurora, the ghostly lights in the sky at high latitudes. Aurora are caused by electrons from space entering the Earth’s atmosphere. They release energy in the electrically-charged areas of the upper atmosphere, emitting visible light and X-rays.

The balloon’s altitude allows X-rays to be observed before they are absorbed by the atmosphere. The balloon also allows a relatively heavy payload to be launched, as compared with satellites, where weight is at a premium.

Further, while a satellite moves very quickly through a large range of areas, a balloon stays relatively stationary.

This permits the researchers to determine whether what they observe is related to the location of its observation or the time of the event.

Millan emphasized the academic value of a balloon-based project, which has a slower timetable than a satellite mission. The extra time lets students take a more active role in the work. They build the equipment, receive the results and analyze the data within the time frame of an advanced degree program.

Also on the X-ray payload is what is called a “piggyback” experiment, using space and weight within the allowed limits but unused by the primary research.

NASA is testing shielding materials for space vehicles. Some payloads have been “fried” by the solar energy, which can be absorbed into the payload vehicle and cause overheating of components.