A schematic mechanical diagram showing both channels of WFC3 is given in Figure 2.1
. Components of the IR channel include: the Channel Select Mechanism (CSM), which directs on-axis light from the HST
OTA to the IR channel; a flat folding mirror; a two-mirror mechanism for providing focus and alignment adjustments; the Refractive Corrector Plate (RCP), which applies the spherical-aberration correction; the IR filter wheel (FSM or Filter Selection Mechanism); and finally the HgCdTe IR detector package.
The WFC3 IR detector is a HgCdTe 1024×
1024 array, with 18 micron pixels, bonded to a silicon multiplexer, with 1014×
1014 pixels sensitive to incoming light. It is a direct descendant of the NICMOS 256×
256 and Hawaii-1 1024×
1024 arrays (more details on the detector are given in Chapter 5