Tuesday, July 1, 2008

Rockets into space


I've been a part of a few interesting organizations in my time but until now none of them has ever launched anything in to space. Jeff Bezos is trying his hand at spaceflight with Blue Origin, but all together too secretly for it to be a fun effort to follow. Elon Munsk, at least, has the audacity to webcast his failures!

But just a few weeks ago the unattractively named GLAST (Gamma Ray Large Area Space Telescope) was put into space atop a Delta II booster. Oddly, this project features a telescope designed and built by the folks at SLAC -- the Stanford Linear Accelerator Center, a 3 mile long underground tunnel and the source of much summer income for me back in college.

What's an underground pipe have to do with space? Simple -- high energy particle detectors. SLAC scientists have considerable experience in building the massive detector assemblies that are used to track collision by-products from particle colliders. Millions (I'm rusty, it might be billions now) of intersecting wire strips, carefully monitored dewars of cryogenic liquid, and massive amounts of computing power trace back the tell-tale fragments of super-accelerated particles and (hopefully) bear witness to the fundamental constituents of matter.

These things are huge. I have to dig around -- I worked there pre-digital photography -- and see if I can find any photos of the SLD, the Stanford Large Detector that was in commission while I was working there. Fifty feet on a side (or more), thousands of tons, and about as far from spaceflight as possible.

GLAST uses the same technology (sort of) to act as a highly sensitive gamma ray telescope, one larger and more sensitive than ever before. Gamma rays emanate from the most powerful and titanic events in the universe -- the collapse of stars, collisions of galaxies, accreting black holes, and all that sort of good stuff. Real Discover Channel fodder. And with plenty of good potential for real science -- these events achieve conditions well beyond anything we can create here on earth, even with massive devices like the LHC and its kin. So while we can't study these fuzzy patches between quantum theory and relativity directly, we can observe what goes on out there in the galaxy, where nature creates a laboratory of unsurpassed energy.

Even more prosaic events have their signatures in the gamma ray, either in transmission/absorbtion or emission. The result is that GLAST is a mission with the potential to answer questions about stellar evolution, dark matter, dark energy, relativity, quantum theory, cosmology, and probably a few other fields that I haven't thought of. This is as much because gamma rays are hard to study as because of the sheer power of GLAST. Its a tough area of the spectrum -- effectively un-focusable, gamma rays can't be detected in any of the intuitive ways. No lenses, no filters, no focal planes will work in the telescope-and-camera paradigm.

Instead, GLAST's unique detector tracks the impacts of gamma rays as they pass through the detector. Yes, through. These guys have so much energy that they don't get bent by lenses, selected by filters, and finally give up their energy in a detector's sensitive well. Instead they pass through the detectors, briefly interacting and producing collision products that are themselves tracked and measured as much as the original photon is!

And perhaps now you understand why a bunch of physicists, and not just astronomers, have had so much to do with GLAST.

But now we will have to wait for the first data release -- expected about a year after launch. GLAST data is quite non-intuitive. Tracking all these collision histories back requires serious computing power and produces a database of events rather than a traditional image.

When it comes, this data will confirm, shatter, and modify theories. It will inspire new rounds of conceptual thought and new generations of thinkers. This project has all the potential to be one of those little gems that gives well beyond its initial scope. I just hope they hurry up with the promised re-naming ceremony and give me something more interesting to say and easier to type than GLAST!

What's perhaps more interesting is that, to the best of my knowledge, GLAST is the only spacecraft to have had an orchestral piece composed specifically for it.


No comments: