1.1 Instrument Overview
Wide Field Camera 3 (WFC3) is a fourth-generation imaging instrument installed on the Hubble Space Telescope during Servicing Mission 4 in 2009. It replaced the extraordinarily successful Wide Field Planetary Camera 2 (WFPC2), thereby ensuring and enhancing the imaging capability of HST in the remaining years of its observing lifetime. WFC3 is the only HST instrument developed as a facility instrument by the HST Project. WFC3 provides HST with high-sensitivity, high-resolution, wide-field survey capability covering a broad wavelength range, from the near-UV at 200 nm to the near-IR at 1700 nm. WFC3 is comprised of two channels, each optimized for a specific wavelength regime:
- Ultraviolet-Visible channel (UVIS): sensitive to 200-1000 nm, with a pair of CCDs covering a 162 × 162" total field of view, with a plate scale of 0.040"/pixel and a focal ratio of f/31.
- Infrared channel (IR): sensitive to 800-1700 nm, an IR focal plane array covering a 136 × 123" field of view, with a plate scale of 0.13"/pixel and a focal ratio of f/11.
WFC3 provides the user with:
- 62 wide-, medium-, and narrow-band filters in the UVIS channel
- 15 wide-, medium-, and narrow-band filters in the IR channel
- 3 grisms: 1 in the UVIS channel and 2 in the IR channel
WFC3 occupies WFPC2's spot in HST's radial scientific-instrument bay, where it obtains on-axis direct images. Light entering from the HST Optical Telescope Assembly (OTA) is intercepted by the flat 45 degree WFC3 pick-off mirror (POM) and directed into the instrument. A channel-select mechanism (CSM) inside WFC3 then diverts the light to the IR channel via a fold mirror, or when the CSM is moved out of the beam, the light enters the UVIS channel unimpeded. Because of this design, only a single channel, either UVIS or IR, can be used at any one time. Figure 1.1 shows a schematic diagram of the instrument's optical and mechanical layout. The main characteristics of each channel are summarized in the following sections. For a technical description of the instrument's properties, performance, operations, and calibration, please refer to the WFC3 Instrument Handbook.
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WFC3 Data Handbook
- • Acknowledgments
- • What's New in This Revision
- Preface
- Chapter 1: WFC3 Instruments
- Chapter 2: WFC3 Data Structure
- Chapter 3: WFC3 Data Calibration
- Chapter 4: WFC3 Images: Distortion Correction and AstroDrizzle
- Chapter 5: WFC3-UVIS Sources of Error
- Chapter 6: WFC3 UVIS Charge Transfer Efficiency - CTE
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Chapter 7: WFC3 IR Sources of Error
- • 7.1 WFC3 IR Error Source Overview
- • 7.2 Gain
- • 7.3 WFC3 IR Bias Correction
- • 7.4 WFC3 Dark Current and Banding
- • 7.5 Blobs
- • 7.6 Detector Nonlinearity Issues
- • 7.7 Count Rate Non-Linearity
- • 7.8 IR Flat Fields
- • 7.9 Pixel Defects and Bad Imaging Regions
- • 7.10 Time-Variable Background
- • 7.11 IR Photometry Errors
- • 7.12 References
- Chapter 8: Persistence in WFC3 IR
- Chapter 9: WFC3 Data Analysis
- Chapter 10: WFC3 Spatial Scan Data