Wide Field Camera 3 - Specifications

Specifications

The instrument is designed to be a versatile camera capable of imaging astronomical targets over a very wide wavelength range and with a large field of view. It is a fourth-generation instrument for Hubble. The instrument has two independent light paths: an optical channel that uses a pair of charge-coupled devices (CCD) to record images from 200 nm to 1000 nm; and a near infrared detector array that covers the wavelength range from 800 to 1700 nm. Both channels have a variety of broad and narrow-band filters, as well as prisms and grisms, which enable wide-field, very-low-resolution spectroscopy that is useful for surveys. The optical channel covers the visible spectrum (380 nm to 780 nm) with high efficiency, and is also able to see into the near ultraviolet (down to 200 nm).

WFC3 features two UV/visible detecting CCDs, each 2048×4096 pixels, and a separate IR detector of 1024×1024, capable of receiving infrared radiation up to 1700 nm.

Both detector focal planes were designed specifically for this camera. The optical channel covers a 164 by 164 arcsec (2.7 by 2.7 arcminute, about 8.5% of the diameter of the full moon as seen from Earth) field of view with 0.04 arcsec pixels. This field of view is comparable to the Wide Field and Planetary Camera 2 and is slightly smaller than the Advanced Camera for Surveys. The near infrared channel has a field of view of 135 by 127 arcsec (2.3 by 2.1 arcminutes) with 0.13 arcsec pixels, and has a much larger field of view than Near Infrared Camera and Multi-Object Spectrometer, which it is designed to largely replace. The near infrared channel is a pathfinder for the future James Webb Space Telescope. The IR channel is designed to lack sensitivity beyond 1700 nm (as compared with the 2500 nm limit for NICMOS) to avoid being swamped by thermal background coming from the relatively warm HST structure. This allows WFC3 to be cooled using a thermoelectric cooler instead of carrying a consumable cryogen to cool the instrument.

The camera makes use of returned space hardware as the structure is built from the original Wide Field and Planetary Camera as well as the filter assembly. These were switched for the Wide Field and Planetary Camera 2 by the servicing mission STS-61 in December 1993.

WFC3 was originally conceived as an optical channel only; the near infrared channel was added later. WFC3 is intended to ensure that Hubble retains a powerful imaging capability through to the end of its lifetime.