Editing Wide Field and Planetary Camera 2

{{Use mdy dates|date=October 2012}}
[[File:Wfpc20101013r.jpg|thumb|Brought back to Earth by the U.S. Space Shuttle, the WFPC is loaded for transport after display at [[JPL]] on its way to its final home at the [[National Air and Space Museum]] in 2010]]
[[File:Quantum efficiency graph for WFPC2-en.svg|thumb|[[Quantum efficiency]] of the [[Charge-coupled device|CCD]] chip in the camera]]
The '''Wide Field and Planetary Camera 2''' ('''WFPC2''') is a camera formerly installed on the [[Hubble Space Telescope]]. The camera was built by the [[Jet Propulsion Laboratory]] and is roughly the size of a [[baby grand piano]]. It was installed by servicing mission 1 ([[STS-61]]) in 1993, replacing the telescope's original [[Wide Field and Planetary Camera]] (WF/PC).  WFPC2 was used to image the [[Hubble Deep Field]] in 1995, the [[Engraved Hourglass Nebula]] and [[Egg Nebula]] in 1996, and the [[Hubble Deep Field South]] in 1998. During [[STS-125]], WFPC2 was removed and replaced with the [[Wide Field Camera 3]] as part of the mission's first spacewalk on May 14, 2009. After returning to Earth, the camera was displayed briefly at the [[National Air and Space Museum]] and the [[Jet Propulsion Laboratory]] before returning to its final home at the Smithsonian's [[National Air and Space Museum]].<ref name=smithsonian>{{cite web|url=http://blogs.smithsonianmag.com/aroundthemall/2009/05/the-camera-that-saved-hubble-coming-to-the-smithsonian/|title="The Camera that Saved Hubble" Coming to the Smithsonian|date=May 27, 2009|access-date=July 14, 2009|archive-date=October 13, 2010|archive-url=http://webarchive.loc.gov/all/20101013042121/http://blogs.smithsonianmag.com/aroundthemall/2009/05/the%2Dcamera%2Dthat%2Dsaved%2Dhubble%2Dcoming%2Dto%2Dthe%2Dsmithsonian/|url-status=dead}}</ref><ref name=nest>{{cite web|title=The Camera That Saved Hubble Leaves the Nest|url=http://www.jpl.nasa.gov/news/news.cfm?id=1&release=2010-335#1|publisher=JPL / NASA|access-date=October 14, 2010|archive-date=February 7, 2012|archive-url=https://web.archive.org/web/20120207100533/http://www.jpl.nasa.gov/news/news.cfm?id=1&release=2010-335#1|url-status=dead}}</ref>

==Design==
WFPC2 was built by [[NASA]]'s [[Jet Propulsion Laboratory]], which also built the predecessor [[Wide Field and Planetary Camera|WFPC]] camera launched with Hubble in 1990. WFPC2 contains internal corrective optics to fix the spherical aberration in the Hubble telescope's primary mirror.

The [[charge-coupled device]]s (CCDs) in the WFPC2 (designed at JPL and manufactured by Loral) detected [[electromagnetic radiation]] in a range from 120 [[nanometer|nm]] to 1000&nbsp;nm. This included the 380&nbsp;nm to 780&nbsp;nm of the [[optical spectrum|visible spectrum]], all of the near [[ultraviolet]] (and a small part of the extreme ultraviolet band) and most of the [[near-infrared]] band. The sensitivity distribution of these CCDs is roughly [[normal distribution|normal]], with a peak around 700&nbsp;nm and concomitantly very poor sensitivity at the extremes of the CCDs' operating range.  WFPC2 featured four identical CCD detectors, each 800x800 [[pixel]]s. Three of these, arranged in an L-formation, comprise Hubble's Wide Field Camera (WFC). Adjacent to them is the Planetary Camera (PC), a fourth CCD with different (narrower-focused) optics. This afforded a more detailed view over a smaller region of the visual field. WFC and PC images are typically combined, producing the WFPC2's characteristic stairstep image. When distributed as non-scientific [[JPEG]] files the PC portion of the image is shown with the same resolution as the WFC portions, but astronomers receive a raw scientific image package which presents the PC image in its native, higher detail.

To allow scientists to view specific parts of the electromagnetic spectrum the WFPC2 featured a rotating wheel which moves different optical filters into the lightpath (between the WFPC2's aperture and the CCD detectors). The 48 filter elements included:

* A set of standard wideband photometric filters.
* A graduated filter, featuring a wide range of very narrowband filters. By positioning the target object at a precise part of the field, the operator can use an accurately picked narrowband filter.
* A number of narrowband optical filters tuned to the wavelengths of various atomic emission lines.

==Performance==

[[File:Small Section of the Carina Nebula.jpg|thumb|Picture of small section of the [[Carina Nebula]] created from images taken with Hubble's Wide Field Planetary Camera 2.<ref>{{cite web|title=Return to the Carina Nebula|url=http://www.spacetelescope.org/images/potw1127a/|work=ESA/Hubble Picture of the Week|publisher=ESA/Hubble|access-date=July 4, 2011}}</ref>]]

As predicted, over the course of its mission the WFPC2 experienced degradation of the CCDs, resulting in defective ("hot") pixels. The telescope's operators performed monthly calibration tests to catalog these; with the WFPC's [[aperture]] closed a number of long exposures are taken, and pixels which differ significantly from near black are flagged. To avoid false positives caused by [[cosmic ray]]s tripping a given pixel, the output of different calibration shots is compared. Pixels which are consistently "hot" are recorded, and astronomers who analyse raw WFPC2 images receive a list of these pixels. Typically, astronomers adjust their photo-processing software to ignore these bad pixels.

WFPC2 was largely superseded for broad-band imaging by the [[Advanced Camera for Surveys]], installed during servicing mission 3B in 2002.  However, the early 2007 failure of ACS resulted in WFPC2 returning to its role as Hubble's primary visible light camera.  WFPC2 was removed from HST during Servicing Mission 4 in May 2009, for return to Earth and eventual museum display. It was replaced by [[Wide Field Camera 3]], which features two UV/visible detecting CCDs, each 2048x4096 pixels, and a separate IR CCD of 1024 x 1024, capable of receiving infrared radiation up to 1700&nbsp;nm.

==See also==
Other HST instruments :
*{{annotated link|Wide Field and Planetary Camera}}
*{{annotated link|Wide Field Camera 3}}
*{{annotated link|Advanced Camera for Surveys}}
*{{annotated link|Cosmic Origins Spectrograph}}
*{{annotated link|Faint Object Camera}}
*{{annotated link|Faint Object Spectrograph}}
*{{annotated link|Goddard High Resolution Spectrograph}}
*{{annotated link|Near Infrared Camera and Multi-Object Spectrometer}}
*{{annotated link|Space Telescope Imaging Spectrograph}}

==WFPC2 images==
<div style="text-align:center;"><gallery>
Image:Jfader hubble.jpg|Hubble Space Telescope WFPC2 image of the [[Hubble Deep Field]] showing the characteristic stairstep composition of WFPC2 images
Image:Eagle nebula pillars.jpg|The [[Pillars of Creation]] within the [[Eagle Nebula]]
File:1994-02-b-full jpg.jpg|WFPC 2 image in 1994 of [[Messier 100|M100 (NGC 4321)]]
Image:Nursery of New Stars - GPN-2000-000972.jpg|[[NGC 604]] in the [[Triangulum Galaxy]]
Image:Bok globules in IC2944.jpg|[[Bok globule]]s
Image:STSci-PRC01-33 omega centauri.jpg|Part of [[Omega Centauri]]
Image:Egg Nebula.jpg|[[Egg Nebula]]
</gallery></div>

==References==
{{reflist|colwidth=30em}}

==External links==
* [http://www.stsci.edu/instruments/wfpc2/ WFPC2 homepage and user's guide]
* [http://hubblesite.org/sci.d.tech/behind_the_pictures/meaning_of_color/index.shtml NASA article explaining how color is built from multiple filtered images]
* [https://web.archive.org/web/20050829195322/http://wfc3.gsfc.nasa.gov/overview/introduction.php Wide Field Camera 3 – NASA]
*[http://www.spacetelescope.org/about/general/instruments/wfpc2.html the WFPC2 at ESA/Hubble]
*[http://www.spacetelescope.org/images/archive/freesearch/wfpc2/viewall/1 Images with the WFPC2 at ESA/Hubble]
*[https://web.archive.org/web/20020605102604/http://wfpc2.jpl.nasa.gov/ WFPC2 Science Team Pages]

{{Hubble Space Telescope}}

{{DEFAULTSORT:Wide Field And Planetary Camera 2}}
[[Category:Hubble Space Telescope instruments]]
[[Category:Space imagers]]
[[Category:Space hardware returned to Earth intact]]