Wfc3 Uvis and Ir Channel Alignment Properties

____________________________________________________________________________ Abstract The purpose of this ISR is to study the sensitivity of the WFC3 UVIS and IR channels to the focus and tilt of their correctors in preparation for the optical alignment of the instrument. This study is done by using the same IDL routines which will be used during the instrument optical alignment at Ball and at GSFC. The IDL encircled energy routine developed by G. Hartig provides excellent performance and is insensitive to under-sampling provided the center is chosen carefully. The IR channel will be aligned at Ball by using a silicon MUX instead of a HgCdTe FPA. We also explore the effect that this will have on the channel focus.