A FAST Way To Study The Aurora

January 29, 1997

FAST STUDY --- Researchers will study the aurora in three dimensions this winter: from space, from jet aircraft, and from ground stations equipped with all-sky cameras. The graphic at right, designed by Geophysical Institute Graphics Artist Deborah Coccia, depicts the FAST satellite flying over an aurora while a Saber 60 jet flies under the display at the same time it is being tracked by ground stations in Alaska at Poker Flat Research Range, Fort Yukon, Kaktovik, and Kotzebue, and in Canada's Northwest Territories at Fort Smith.

While the aurora decorates Alaska's dark skies this winter, scientists from around the country will gather at Poker Flat Research Range to participate in one of the most intensive studies ever performed on the northern lights.

While a small satellite orbits high overhead, researchers will monitor brilliant auroral displays simultaneously in three dimensions: from space, from jet aircraft, and from the ground.

The satellite, known as the Fast Auroral Snapshot (FAST) Explorer, will guide the three-dimensional study as it gathers data about the aurora while orbiting 4200 km (2610 miles) above the polar north. The unusual experiment is designed to help scientists understand the physics behind what is happening at high altitudes to energize brilliant auroral displays seen from Earth.

Scientists know that auroras are created when electrical energy extracted from solar wind flows down Earth's magnetic field lines to form ring-shaped regions around the north and south geomagnetic poles. However, they don't know what causes the aurora to appear as thin, undulating curtains, or in shapes as various as folds, curls, rays, or flickering arcs.

"The physics governing what shapes the aurora is important because it is similar to the physics governing little-understood processes that occur throughout 99 percent of the universe," said FAST principal investigator Charles Carlson, a research physicist at the University of California at Berkeley.

Geophysical Institute Professor Hans Nielsen compares the auroral displays seen on Earth to an image seen on a television screen. Scientists know the sun is the power source of the aurora, just as electricity is the power source of a television set.

"Using this analogy, the FAST satellite is designed to fly back in the inner workings of the TV, where the picture is forming," Nielsen said. "We want to find out exactly how the auroral picture forms and what processes create it."

Nielsen will participate in the FAST campaign by flying in a jet equipped with cameras needed to capture the aurora on video tape at the same time the satellite is flying overhead. Auroras generally arc from east to west across Interior skies, while the 400-pound satellite, which was launched in August from under the belly of a jumbo jet, is traveling in an elliptical orbit that runs north and south.

Nielsen will fly above any potential cloud cover to the place where the aurora lies directly under the path of the satellite and take simultaneous measurements with a narrow field, high-resolution camera. In a special Saber 60 jet, Nielsen is scheduled to make at least 15 flights under the satellite as it passes over different auroras.

"By combining the measurements from air and space, we'll be able to see each aurora from the north, south, east, and west," Carlson said. "We'll get detailed measurements of a much bigger area than is possible with a satellite track alone."

Meanwhile, Geophysical Institute Professor Tom Hallinan will record the aurora with all-sky cameras at ground stations in Alaska at Poker Flat, Fort Yukon, Kaktovik, and Kotzebue and in Canada's Northwest Territories at Fort Smith. The all-sky camera images will show general broad-scale features of each aurora being analyzed by the satellite and jet aircraft.

Carlson chose to base his research out of Poker Flat because the range is equipped to gather data from the FAST mission and because it lies in a good position on the globe.

FAST travels in an eccentric orbit, which means it circles the planet in an elliptical pattern, coming close to Earth on one side and flying high above it on the other. During January and February, the FAST satellite will orbit high enough above the northern hemisphere to view auroras daily throughout the entire polar region. "The satellite will be orbiting high enough that it will be possible to see FAST from the tracking station at Poker Flat even when it orbits over Sweden," Carlson said.

As the satellite travels over the northern aurora, it will send data directly to the ground in real time. Instant data collection and the ability to control the instruments aboard FAST from the ground are two reasons why a team of scientists will remain at Poker Flat throughout all of January and February.

"Scientists will analyze data on the spot with every pass FAST makes over the aurora," Carlson said. "We will be able to identify key new measurements and reconfigure instruments immediately to make sure we are maximizing the quality of the data."

FAST, the second satellite in a series of small explorer missions launched by the National Aeronautics and Space Administration, carries "burst detectors" so the ground-based crew won't be overwhelmed with data. Burst detectors are designed to turn on and start recording in high-resolution mode only when parameters indicate that auroral conditions are interesting. "We only want to receive data on what we consider to be the absolute best auroral conditions," Carlson said.

Those parameters can be changed from the ground to suit a researcher's needs. "With selective data gathering, we can avoid collecting hours and hours of empty data taken when the satellite is not traveling through an aurora," Carlson said.

While scientists at Poker Flat view the aurora on the night side, an international team of researchers in Svalbard, Norway, including professors and graduate students from the Geophysical Institute, will observe the aurora on the day side.

Day side auroras, which look similar but are more broken and not as brilliant as those occurring on the night side, make it easy for researchers to investigate Earth's magnetospheric cusp, the chimney that lets particles from the solar wind directly into the atmosphere, according to Charles Deehr, Poker Flat's scientific director. When FAST travels through the magnetospheric cusp over Svalbard, it will send data to the European Space Station in Kiruna, Sweden, for analysis later.

The FAST mission was designed to produce data similar to that obtained from sounding rockets Carlson launched from Poker Flat during the 1980s. Sounding rockets can transmit high-resolution data from a single aurora rapidly, while most satellites can measure only the general properties of many auroras. Small satellites combine the best of both methods because they permit high-resolution data transmission while analyzing a variety of auroras. "In the late 1980s, interest grew in small satellites and the study of the aurora was perfectly suited," Carlson said.

While FAST is in orbit, scientists throughout the northern hemisphere will collect data to support the mission from a variety of sources, including magnetometers, rockets, and other satellites. University of California Professor Cynthia Cattell, one of the 10 coinvestigators for the FAST mission, and a former Geophysical Institute graduate student, started an International Aurora Study to encourage researchers from around the world who are taking measurements on the aurora to share them on a homepage. The address for the new International Aurora Study homepage is http://bolero.gsfc.nasa.gov/ias/ias.html.

University of Alaska Fairbanks, Geophysical Institute

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