X-Ray
Spectrometer (XRS)
is a system of X-ray microcalorimeters that sit behind an imaging X-Ray
Telescope (XRT). The instrument roughly covers the energy range of
0.3 - 10 keV. XRS is a spectrometer, an instrument that separates
light signals into different frequencies, producing a spectrum
(See our primer on
spectroscopy). XRS is special because, for the first time,
it will provide both high spectral resolution and high throughput
in one instrument.
High spectral resolution means being able to distinguish small
differences in the energy of X-ray
photons.
This allows us to see much finer detail in the spectrum.
High spectral resolution is a key to being able to see and interpret
emission lines from different elements; these emission lines are a
powerful tool for learning about the objects in our universe
(black holes, clusters of galaxies, etc.).
Another important property of XRS is that it is very sensitive:
scientists use the term "high throughput."
XRS will achieve this first by having a large area XRT, which
works like the lens of a camera, focusing the X-rays on the XRS detector.
Also, the XRS itself is designed so that nearly all the X-ray photons
that hit it are detected and measured. This means it can collect and
detect enough photns to be useful, even from weak sources.
XRS has been developed by a collaboration of Goddard Space Flight Center
and University of Wisconsin in the US; and Institute of Space and Astronautical
Science (ISAS) and Tokyo Metropolitan University in Japan.
The next section will explain how the microcalorimeter, along with the
other components of the XRS, works to measure energy.
