Characterization of infrared filters for the wide-field camera 3 of Hubble Space Telescope

Abstract

The Wide Field Camera 3 (WFC3) is a panchromatic imager that will be deployed in the Hubble Space Telescope (HST) in 2004. The mission of the WFC3 is to enhance HST's imaging capability in the ultraviolet, visible and near-infrared spectral regions. Together with a wavelength coverage spanning 2000A to 1.7 microns, the WFC3 high sensitivity, high spatial resolution, and large field-of-view provide the astronomer with an unprecedented set of tools for exploring all types of exciting astrophysical terrain and for addressing many key questions is astronomy today. The filter compliment, which includes broad, medium, and narrow band filters, naturally reflects the diversity of astronomical programs to be targeted with WFC3. The WFC3 holds 61 UVIS filters elements, 14 IR filters, and 3 dispersive elements. Accurate and comprehensive knowledge of the optical performance of these components including its pass-band and out-of-band rejection behavior are necessary to verify that the instrument will meet its scientific objectives. The measured throughput curves are essential components in instrument performance models used to plan observations, and in calibration algorithms for removing the instrument signature from in-flight data. We will report on the normal incidence in-band and out-of-band transmittance of the IR filters measured near the operating temperature of -30 degree(s)C and additional tests used to characterizes the filter's performance. Details of the characterization apparatus, that include an optical cryostat, and a grating spectrometer are discussed.