1.2. Overview

The Wide Field Camera 3 (WFC3) is a fourth-generation imaging instrument. It was installed in the Hubble Space Telescope (HST) during Servicing Mission 4 (SM4) in May 2009. WFC3 saw first external light on June 24, 2009, following the cooling of its detectors. Servicing Mission 4 Observatory Verification (SMOV) activities were completed in late August 2009, and were followed by the Cycle 17 calibration and science programs (see Appendix 3.2 for the SMOV calibration plan and Appendix E.3 for the Cycle 17 calibration plan). 

This WFC3 Instrument Handbook has been prepared by the WFC3 team at STScI. It is the basic technical reference manual for WFC3 observers. The information in this Handbook is intended to be useful for Cycle 33 Phase I proposers, for the subsequently selected General Observers (GOs) as they prepare their Phase II specifications, and for those analyzing WFC3 data. The WFC3 Data Handbook provides an overview of architecture, calibration, and analysis of WFC3 data. The HST Primer and the HST Call for Proposals also contain valuable information for proposers, and the HST Call for Proposals is the final authority on HST policy.

This edition of the WFC3 Instrument Handbook (Version 17.0) was written during the execution of the Cycle 32 calibration plan and the beginning of the Cycle 33 calibration plan (see Appendix E for cycle cadence and calibration programs). It supersedes Version 16.0, and includes results from analysis of most calibration programs executed through Cycle 32. See the Documents Archive for links to Instrument Handbooks from previous cycles.

The WFC3 instrument occupies HST’s radial scientific-instrument bay, from where it obtains on-axis direct images. During SM4, the shuttle astronauts installed WFC3 in place of the long-serving Wide Field Planetary Camera 2 (WFPC2). WFPC2, in turn, was installed during SM1 in December 1993, to replace the original Wide Field/Planetary Camera (WF/PC1). WFC3, like WFPC2, contains optics that correct for the spherical aberration discovered in the HST primary mirror following launch of the telescope in April 1990.

WFC3 is designed to ensure that HST maintains its powerful imaging capabilities until the end of its mission, while at the same time advancing its survey and discovery capability through WFC3’s combination of broad wavelength coverage, wide field of view, and high sensitivity. WFC3 also provides a good degree of redundancy for the Wide Field Channel of the Advanced Camera for Surveys (ACS) and has replaced some of the capabilities of the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS).

A key feature of WFC3 is its panchromatic wavelength coverage. By combining two optical/ultraviolet CCDs with a near-infrared HgCdTe array, WFC3 is capable of direct, high-resolution imaging over the entire wavelength range from 200 to 1700 nm. In addition to a comprehensive range of wide-, intermediate-, and narrow-band filters for imaging, WFC3 is also equipped with multiple grating prisms (grisms) to allow for wide-field slitless spectroscopy. Together, these features ensure WFC3 has broad applicability to a variety of ongoing and cutting-edge astrophysical investigations. 

WFC3 is a facility instrument. It was developed, constructed, characterized, and calibrated by an Integrated Product Team (IPT) led by NASA’s Goddard Space Flight Center (GSFC), and composed of staff astronomers and engineers from GSFC, STScI, Ball Aerospace & Technologies Corp., the Jet Propulsion Laboratory (JPL), and other industrial contractors. 

A Scientific Oversight Committee (SOC), selected by NASA from the international astronomical community and appointed in 1998, provided scientific advice for the design and development of WFC3 (for the list of SOC members, see Acknowledgements). The SOC’s activities were in a range of areas, including: defining the key scientific goals and success criteria for WFC3; participating in project reviews; recommending an optimum set of filters and grisms for the instrument and the pixel scale and field of view of the detectors; participating in the selection of flight detectors; and advising on technical trade-off decisions in the light of the scientific goals of the instrument.