CDS : Coronal Diagnostics Spectrometer
CDS observes the solar corona in ultraviolet radiation. It looks at small pieces of the Sun just a few times the size of the Earth! It can observe the Sun in radiation that comes from plasma with a range of temperatures, and it can observe these different temperature plasmas all at the same time. From these data it is possible to calculate the temperature, density and speed of the solar material being looking at.
CDS can observe the atmosphere in great detail, so very fine structures can be seen. The instrument can take new observations every few seconds, so changes in the corona can be followed very accurately.
Pictures courtesy of the SOHO CDS consortium.