Mercury MESSENGER Spacecraft Detector

Lawrence Livermore National Laboratory (LLNL) physicist Morgan Burks describes the gold-plated detector developed by LLNL and placed aboard NASA's Mercury MESSENGER spacecraft, designed to provide information about the elements and minerals found on the planet closest to the Sun.

Transcript

00:00:00 What I’m holding here is the prototype of the gamma ray spectrometer that our group sent on the Mercury MESSENGER mission to Mercury. It is a germanium-based gamma ray spectrometer. It’s a high resolution gamma ray detector, and the reason that it’s gold plated, and it’s polished and gold plated, is that this is to act as infrared shielding for the detector, because, although this technology is very high resolution, it has the big drawback that to operate, it has to run at minus 200 degrees Celsius, about minus 330 Fahrenheit. So this is especially complicated at Mercury, the closest planet to the Sun, because of extremely harsh thermal environment there. And the way you cool the detector in such a harsh thermal environment is, first, is to have lots of infrared shielding, which reflects the Sun’s heat, and reflects the heat off the.. coming from the planet. And

00:01:00 so a highly polished gold plated surface reflects about 98 percent of infrared light. So what we have is, in capsulation with our germanium detector inside, and around it we have several infrared shields and the whole thing is suspended on a Kevlar.. set of Kevlar fibers to isolate it mechanically from the outer hot body. We’re really getting excited now. The instrument’s been in flight for nearly seven years. Of course it was very exciting when it launched, but we’ve just sort of been waiting, and we’ve been off doing other work. So now that it’s actually approaching orbit, approaching turn-on of the instrument, we’re all very excited. We’ve been having conference calls. We’ve been reviewing the plans of what we’re going to do for testing and evaluation and so on. And so yes, a pretty exciting time. And we’ll definitely all rest a little easier

00:01:54 once we see the first data coming down. So the purpose of having a gamma ray spectrometer on this NASA mission at Mercury is that the surface of Mercury is highly radioactive. It’s bombarded by cosmic rays from space. Unlike Earth, Mercury is not protected from those cosmic rays because it doesn’t have a thick atmosphere, and it doesn’t have a strong magnetic field; both of those things, which protect Earth. So Mercury is highly radioactive. So our instrument in orbit can detect those gamma rays, and it turns out that gamma rays act like a fingerprint for the elements that emit them. So if you can measure those gamma rays with high resolution, you can determine the surface composition of the planet. And that’s very important to help discriminate between various formation theories, to help them understand how the

00:02:45 planet formed and what its geological history is.