The abbreviation HCI is used for High Contrast Imaging generally meaning imaging of an object that is very near a bright object, such as imaging an Extra-Solar Planet despite the much-brighter light from its parent star. Generally, a Coronagraph is incorporated into the instrument or observation.
High Contrast Spectroscopy (or High Contrast Spectrography, or sometimes HCS) is Spectrography of such targets. Post-processing is used to isolate the planet's spectrum through knowledge of the star's spectrum, which inevitably is not entirely suppressed, despite the coronagraph. A Spectrograph with a high Spectral Resolution assists in this improvement of the Signal-To-Noise Ratio.