A bit of excitement to brighten the otherwise pensive mood in my research group today. Courtesy of the good folks at the National Scientific Balloon Facility (NSBF), BLAST went up, up, and away today. Now we can all watch it float its way around the Arctic Circle at 40 km altitude from Sweden towards Canada. The photos on the grad student blogs (here and here) are perhaps more interesting. There's even videos of the launch process, which looks to have been mercifully smooth after a long string of delays.

Now don't get me wrong, BLAST has a completely different purpose in life than the project I'm involved with. Their lowest observing frequency is comparable to our highest. Thus, where EBEX will be sensitive to the microwave background, BLAST is primarily going to see dust in our own galaxy, with a smattering of high-redshift starburst galaxies thrown in for good measure. Nonetheless, balloon-based submillimeter astronomy isn't all that big a field, and the technology is pretty closely related across the board. So we work with some BLAST folks, and we get to be excited for them.

After all, the basic problem we're attacking is almost identical, from an engineering standpoint. We all want to be able to measure the energy emitted by astrophysical sources that (after redshifts) look to be only a few degrees above absolute zero (i.e. a few Kelvin).

Problem: CCDs and other camera-like technologies don't remotely work this far out in the infrared. Thus we all use variants on the bolometer, conceptually not unlike those new-fangled infrared thermometers that take your temperature when pointed at you.

Problem: Thermodynamics ensures that the thermal noise from a room-temperature detector would massively swamp the signal from the sort of cold sources we're looking at. In fact, to get a good signal-to-noise ratio, submillimeter detector arrays should be kept at a fraction of a Kelvin. Thus the need for big ol' cryostats full of liquid helium.

Problem: Water vapour absorbs submillimeter radiation, rendering the atmosphere mostly opaque at these wavelengths. Since launching a satellite is expensive as all get-out and rather a lengthy process to boot, those of us who want to try crazy new ideas or just get the drop on the competition (*ahem*, lay the groundwork for successor experiments) can use balloons to carry experiments largely above the atmosphere for several days.

And so on, and so forth. There are some important differences, but these are essentially details. Different frequencies require some different materials. To measure the tiny polarized component of the CMB we will need much greater sensitivity, which we're mostly getting through the use of an absurd number of detectors. Newer technologies to choose from by the time we actually build our instrument.

Then of course there's the Eeeeevil Super-LASER of DOOMEM. I'm just sayin', we should throw one in and blackmail the world for greatly increased funding of basic research. That would be new. BLAST doesn't have one.

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This page contains a single entry by Milligan published on June 12, 2005 8:40 PM.

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