Frontiers

BLAST Blasts Off Again

Graduate student Brad Dober works to map out the night sky.
May 2012

It’s a safe bet that most scientists don’t believe in reincarnation. But they’ll have to make an exception for the BLAST balloon-borne telescope. Aside from the schedule delays and routine technical glitches that inevitably plague complex scientific projects, it’s already survived broken mirrors, sun-melted components, bitter polar winters, and being dragged by the wind for 120 miles across the trackless Antarctic wilderness.

And in the next Antarctic summer, in late 2012 or early 2013, the latest incarnation of BLAST (Balloon-borne Large Aperture Submillimeter Telescope) will rise again from the ice. With a new name (BLASTPol) reflecting a new mission, the telescope continues to be a testament to scientific ingenuity, tenacity, and the sheer cussedness of dedicated researchers. Joining them this time will be a new member of the team, second-year graduate student Brad Dober.

“The observed results show stars to form much slower than gravitational models would predict. So something’s holding the gas up and preventing it from collapsing.” - Brad Dober

Conceived and built by Reese W. Flower Professor of Astronomy and Astrophysics Mark Devlin, BLAST was originally designed to probe primordial galaxies at the edge of the visible universe. Because it observes at submillimeter wavelengths of light that are largely blocked by our atmosphere, BLAST rides a NASA balloon to an altitude of about 25 miles, at the edge of space. The original BLAST made two science flights, one in Sweden in 2005 and a second in Antarctica in 2006, but Murphy’s Law struck both times. In Sweden, the main telescope mirror cracked on launch, compromising most of the data collection. And after BLAST set down on the ground at the end of the Antarctica flight, its recovery parachute failed to detach and caught the wind, dragging the gondola across the landscape for 120 miles. By sheer luck, the instrument capsule containing the hard drives with all the priceless science data was recovered intact, but BLAST itself was a wreck.

Devlin and his team rebuilt the instrument as BLASTPol and gave it a new mission: mapping polarized light from star-forming molecular clouds in our galaxy in an effort to answer some long-standing questions about how stars form. One mystery is the discrepancy between theoretical models of how stars form from the gravitational collapse of dust clouds and the formation process as it’s actually observed. “The observed results show stars to form much slower than gravitational models would predict,” says Dober. “So something’s holding the gas up and preventing it from collapsing. Most theories are it’s some kind of magnetic field in the cloud from the ionized plasma.” That’s where BLASTPol comes in. Because polarization is a tracer of magnetic fields, mapping the polarized light from star-forming clouds provides a key window into the behavior of magnetic fields inside the stellar nursery.

BLASTPol’s first flight in Antarctica in 2010 featured another glitch when a Mylar sun screen focused too much heat on a new infrared filter and melted it during flight. Dober’s first job upon joining the BLAST team last year, with the help of Tristan Matthews from Northwestern University, was to figure out just what had gone wrong and how to fix it. His undergraduate experience at the University of Wisconsin, working on sophisticated instruments for rocket experiments, helped him to resolve the problem quickly.

With the BLASTPol telescope now fully repaired and redesigned, Dober is looking forward to his first Antarctic trip. “The rest of the team has all gone once on the first BLASTPol flight, so they’re battle-hardened and ready to go for another round. It’s my intention to go on the flight.” Preparations at McMurdo Station will begin sometime in October, working up to the actual flight in January.

It’s a keenly anticipated event among astronomers. “BLASTPol is the only polarization-sensitive telescope of its kind in existence right now,” Dober explains. “BLASTPol is the first instrument to combine the sensitivity and mapping speed necessary to map magnetic fields across entire clouds with the resolution to trace fields down into dense substructures, including cores and filaments.” Yet Devlin, Dober and their colleagues have already submitted a proposal to NASA for the next step: Super BLASTPol, an instrument of even greater resolution and mapping speed. Dober’s next project will be designing and building the detectors for the new telescope.

The BLAST team also hopes to make the benefits of balloon-based science more widely available. “We’re going to try to shift ballooning into a new phase,” Dober says. “We’re going to try to open 25 percent of the balloon flights to a shared-risk kind of observing, accepting proposals from the rest of the scientific community on targets that we should hit with our telescope.” With scientific access to space ever-more expensive and limited after the end of NASA’s Space Shuttle program, BLAST serves as a model and inspiration for how much valuable science can be done with just a balloon, a well-built instrument, and an ingenious, dedicated, and indomitable team of people.