Wednesday, August 29, 2007

The harsh realities of polar regions

Argen Duncan El Defensor Chieftain Reporter, aduncan@dchieftain.com

ADUNCAN Staff members of the seismic research program at New Mexico Tech are developing equipment to operate in the harsh conditions of polar regions, and some are to visit Antarctica, all to support international research.

The Incorporated Research Institutions for Seismology-Program for the Array Seismic Studies of the Continental Lithosphere is creating seismic stations to operate in extreme cold, run for 26 months on its own power system and transmit data with a modem like a satellite phone. The seismic stations are designed for a range of experiments from looking at the structure of the Earth's core and the deep crust to studying earthquakes that traveled from the other side of the world.

Staff members are also developing techniques to deploy the stations in places where no one has ever left them year-round.

The three-year program involves two initiatives: one to acquire seismic stations and necessary operating equipment and another to develop autonomous power and communication systems.

"Our main goal is to return a 100 percent data set," said IRIS-PASSCAL Polar Program Manager Tim Parker.

Any experiment in Antarctica costs millions of dollars and he wants to make the cost worth it.

PASSCAL will also deploy four people to support experiments, Parker said. PASSCAL supports research, rather than conducting it.

For seven months, two test pads of the new seismic stations at the South Pole and one on the flank of Mount Erebus have been running.

Tech Professor of Geophysics Richard Aster, principal investigator in Tech's part of an international study of the West Antarctic ice cap and geology under it, is to employ 10 of the seismic stations for that project to start with, said IRIS-PASSCAL Director Bruce Beaudoin. For Aster's study on the Antarctic volcano Mount Erebus, he is to use another 25 stations.

Beaudoin said 10 more stations are earmarked for research on mountains hypothesized to exist under the ice of the highest Antarctic plateau.

"They're ramping up to more equipment next year," Beaudoin said of the projects.

PASSCAL is working with a geographic positioning system support group on the National Science Foundation-funded project.

Aster said Antarctica has conditions that make it hard to do the necessary kind of earth imaging.

Parker said most seismic equipment can operate in temperatures no lower than 4 degrees below zero on the Fahrenheit scale. PASSCAL's stations must withstand temperatures of 94 degrees below zero.

"The average year-round temperature, summer and winter, is minus 55 degrees Fahrenheit," Aster said of his comparatively warmer region of study.

In winter, temperatures can drop to more than 100 degrees below zero in some places.

Parker said the design he and engineer Brian Bonnett developed with support from others has a "fancy" enclosure to trap and use heat from the digitizer. This procedure raises the temperature 77-86 degrees above the ambient temperature.

"And to avoid the big temperature swings, you bury that box in the snow, which is minus 55 Centigrade (minus 67 degrees Fahrenheit), most of the time," Parker said.

Also, scientists must power instruments where it's dark six months of the year. Beaudoin said the stations must run on batteries rather than external power.

Parker said the instruments have a throwaway primary battery system and a system that recharges with sun or wind. Designers can't connect the two systems because it would damage the primary battery.

"So we're using very expensive lithium batteries that are super light weight," Parker said.

The batteries operate at temperatures no lower than 58 degrees below zero, which makes the heat-saving enclosure necessary.

Data recovery also presents a difficulty.

"And we're working on new satellite telemetry options that can actually send data back from Antarctica using low orbit satellites," Aster said.

With stations collecting five to six gigabytes of data a year, Parker said, the existing Antarctic communication system can't handle the information. The seismic stations use iridium modems, like a satellite phone, to move state-of-health information and some data on the limited bandwidth.

Parker said seismic stations must be minimum payloads for aircraft. With limited time to use planes in Antarctica, designers are working to create stations that can be assembled in one trip.

Also, Aster said stations must be autonomous because visits would cost a lot and bad weather could prevent them.

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