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| On October 31, 2006, NASA Administrator
Mike Griffin announced that there will be another servicing mission
(SM4) to Hubble . Read NASA Press Release
During Servicing Mission 4 (SM4), seven astronauts will approach and enter Hubble's orbit aboard a space shuttle. The astronauts will use the shuttle's robotic arm to grapple and harness Hubble into its bay.
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From there, the extensively trained astronauts will perform the maintenance and upgrade operations of SM4. This includes the procedure of removing WFPC2 from Hubble's Radial bay and replacing it with WFC3. WFC3 will maintain the same mechanical and electrical interfaces as WFPC2.
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Optimum Position on the Focal Plane ||| |
When
Hubble receives light, its optical system images the
sky on to a focal plane that is just behind the primary
mirror. After the next servicing mission, this focal
plane will be shared by the five scientific instruments
(WFC3, COS, ACS, NICMOS, and STIS) and three fine guidance
sensors (FGS's).
The pick-off mirror
of WFC3 (like WFPC2 before it) will occupy the very
center portion of the HST focal plane, a section that
has a relatively large field-of-view and minimal optical
distortion. A large field-of-view allows for the capturing
of light from a large portion of the sky, while the
low distortion improves sensitivity and simplifies data
analysis.
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