When gasses are very hot, you can no longer
observe the distinct spectral lines. Instead, the motion of the
atoms or molecules causes the lines to smear out or broaden. This
is known as Doppler Broadening. Instead of spectral
lines, a hot gas will have a continuous spectrum.
The continuous spectrum of a hot gas can be used to measure the temperature of the gas. Even though a hot gas will emit light across the entire spectrum, certain wavelengths of light will be more intense than others depending on the temperature. Hotter gasses will have more high frequency wavelengths than low frequency gasses - in other words, they will be "bluer."
Click here (outside site) to observe how color and temperature are related.
The CHIPS instrument will be observing light from the ISM in the extreme ultra-violet region.