The ACIS has two arrays of CCDs, one (ACIS-I) optimized for imaging wide fields (16x16 arc minutes) the other (ACIS-S) optimized as a readout for the HETG transmission grating. One chip of the ACIS-S (S3) can also be used for on-axis (8x8 arc minutes) imaging and offers the best energy resolution of the ACIS system.
The HRC comprises two micro-channel plate imaging detectors, and offers the highest spatial (<0.5 arc second) and temporal (16 msec) resolutions. The HRC-I has the largest field-of-view (31x31 arc minutes) available on Chandra. The HRC-S is most commonly used to read out the dispersed spectrum from the LETG.
The HETG is optimized for high-resolution spectroscopy of bright sources over the energy band 0.4-10 keV. It is most commonly used with ACIS-S. The resolving power (E/ΔE) varies from ~800 at 1.5 keV to ~200 at 6 keV.
The LETG provides the highest spectral resolving power (E/ΔE > 1000) on Chandra at low energies (0.07 - 0.2 keV). The LETG/HRC-S combination is used extensively for high resolution spectroscopy of bright, soft sources such as stellar coronae, white dwarf atmospheres and cataclysmic variables.