16416

This program acquires scanned observations for monitoring the relative changes in the WFC3-UVIS photometric throughput. The spectrophotometric white dwarf standard stars GD153 and GRW70 comma and G-type star P330E comma are scanned in a subset of filters periodically over the year. Historically comma this program was intended as a monitor of the UV filters as they provide a means to detect contaminants on the instrument optics comma with one or two visible-red filters serving as a control. Since then comma additional filters in the visible and red have been added to the program to expand the monitor to longer wavelengths. The observing cadence is roughly once a month though some exceptions are required to accommodate visibilities.