“BLAST!” is a documentary about the Balloon-Borne Large Aperture Sub-millimeter Telescope, and it opens with this teaser:
The telescope is that huge instrument on the end of crane. It’s supposed to measure light in the far infrared from the early universe. Its builders had been down in Antarctica for months putting it together. Just as the balloon lifts off and starts to pull it upwards, it swings back and crashes into the crane. The principal investigator, Mark Devlin of U. Penn, was not a happy NASA customer, as expressed above.
And then they cut away! You have to watch the rest of the movie to find out what happens. You’re welcome to catch it on Netflix here, but I’ll spoil it for you.
The telescope did go up successfully and flew for 11 days in 2006 across Antarctica, and then came down as planned. It captured data too quickly to radio it anywhere, and so it was all recorded on a hard drive in a sealed pod. Unfortunately, the parachute didn’t release on landing. It dragged the scope for 120 miles (!) across the ice in 24 hours. There’s a sign of just how barren Antarctica is – you couldn’t drag something for 2 miles anywhere else without snagging on something. The scope was smashed to bits. The researchers flew out to the scope’s final resting site, desperately hoping to find the hard drive pod. Unfortunately it was painted – white. They had to search a 120 mile snowy track for one white box. Miraculously, they found it only 3 miles away and managed to recover the data.
The scope was made to image distant galaxies in the far infrared at wavelengths of 100, 250, and 500 um. That kind of light never makes it to the Earth’s surface, so they lifted the scope to 120,000 feet with a helium balloon. They did it in Antarctica because the sun never sets in the summer time, letting the scope’s solar cells power it continuously, and preventing the balloon from sagging in the cool of the night.
Every time astronomers look at a new spectral band they find something interesting, and that was true here too. It turns out that light from early stars would get absorbed by dust clouds, re-radiated at 100 um, and then red-shifted to 200 to 500 um. Redshifts of 1 to 4 correspond to ages of 1.5 to 6 billion years after the formation of the universe. There’s a huge amount of energy in this band, indicating that there was a lot more star formation going on at this period than we see today. And a good thing that was too, since those early stars formed the heavy elements that we’re composed of. Most of the far infrared light that we see today comes from those early stars. Here’s the abstract for the Nature paper: “Over half of the far-infrared background light comes from galaxies at z ≥ 1.2″ .
The movie was made by Mark Devlin’s brother, Paul, who has done several other documentaries at Devlin Pix. It centers on the first two flights of BLAST, one from Sweden and the one in Antarctica. The Swedish flight was a bust. They were held up by rain for weeks, and then the focus drifted so much that the data was unusable. They rebuilt the scope so they could tune the focus in flight and had much more success the second time. It still meant being away from their families for months. There’s a quite poignant scene where Devlin is calling home from McMurdo at Thanksgiving and his young son refuses to talk to him. That’s the strain of long field work.
Yet this is kind of a beau ideal of science. It doesn’t need massive semi-military expenditures, it takes people to exotic places, and it finds out interesting things. When the movie came out, Devlin went on the Stephen Colbert show to promote it. Devlin happens to be completely bald, so Colbert asked him “Now, you spend a lot of time in Antarctica, you send things up to the edge of space – you’re Lex Luthor, aren’t you?” What every kid geek aspires to!
It turns out that there’s a lot of this kind of balloon-borne astronomy. It’s radically cheaper than satellites, but let’s you get to new wavelengths. This list of stratospheric balloon launches shows dozens of new ones each year. The flights are currently limited to only few days in length, and even that is only near the poles. The reason is that current balloons cool down at night and lose too much altitude. They have to drop ballast to stay up, and the amount of ballast limits the flight time. However, there’s a new technology, Superpressure Balloons, that keep the same volume by over-pressuring the envelope during the day and relaxing it at night. They have stayed up for 41 days, and NASA is aiming for 100. They need envelopes twice as thick as zero-pressure balloons and so can’t lift as much payload, but they could take balloon astronomy to a whole new level.
The field even has its crackpot fringe in the form of operations like JP Aerospace. They talk grandly of Airship To Orbit, building three lighter-than-air craft that will provide cheap access to space:
- A 1000 ft Ascender blimp which takes a crew to:
- Dark Sky Station (love that name), a permanent manned structure with 3-mile-long arms at 140,000 feet. It supports observatories and tourism, and is the construction platform for:
- A 6000 ft orbital vehicle driven by an ion engine. It takes 5 days to accelerate to orbital speed, climbing all the while.
Hey, I’d visit! Better that than the 15 minute ride on Spaceship Two. Too bad it’s a do-it-yourself volunteer operation out near Sacramento. So far they’ve built a 150 foot scale model of the Ascender, and have tried out a few of the technologies on weather balloons.
Still, the BLAST work is quite real, and they just flew another mission last year. That’s the sort of project that gets grad students excited!