Tip:
Highlight text to annotate it
X
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
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
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
planet formed and what its geological history is.