Editing Space Interferometry Mission (section)

===Planet hunting===
[[Image:NASASimLiteMissionCapabilities.jpg|thumb|alt=This chart depicts the potential number of habitable planets and other planets that SIM Lite might have detected. The number of one-Earth mass planets assumes 40% of mission time is assigned to the search.|This chart depicts the potential number of habitable planets and other planets that SIM Lite was expected to detect. The number of one-Earth mass planets assumes 40% of mission time is assigned to the search.]]
SIM Lite would have been the most powerful [[extrasolar planet]] hunting [[space telescope]] ever built.<ref name=davidson>Davidson, John et al., Ed., [http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/simBook2009/ SIM Lite Astrometric Observatory]  {{webarchive|url=https://web.archive.org/web/20100409140747/http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/simBook2009/ |date=9 April 2010 }}, [http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/SIMLiteBook/Front-Material-LR.pdf Executive Summary] {{webarchive|url=https://web.archive.org/web/20090827041834/http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/SIMLiteBook/Front-Material-LR.pdf |date=27 August 2009 }}, p. ix et seq., Jet Propulsion Laboratory 400–1360, 2009.  Retrieved 8 March 2010.</ref> Through the technique of [[interferometry]] the spacecraft would be able to detect Earth-sized planets.<ref name=davidson/> SIM Lite was to perform its search for nearby, Earth-like planets by looking for the "[[Methods of detecting extrasolar planets|wobble]]" in the parent star's apparent motion as the planet orbits. The spacecraft would have accomplished this task to an accuracy of one millionth of an [[arcsecond]], or the thickness of a [[Nickel (United States coin)|nickel]] viewed at the distance from Earth to the [[Moon]]. Titled the Deep Search, the planet hunting program was intended to search approximately 60 nearby stars for [[terrestrial planets]] (like [[Earth]] and [[Venus]]) in the habitable zone (where liquid water can exist throughout a full revolution (one "year") of the planet around its star). The Deep Search was to be the most demanding in terms of [[astrometry|astrometric]] accuracy, hence the name, Deep Search.<ref name=davidson/> This program would have used the full capability of the SIM Lite spacecraft to make its measurements.<ref name=davidson/>

A flexible search strategy<ref name=aas08>{{cite journal |date=2008 |title= Taking the Measure of the Universe: Precision Astrometry with SIM PlanetQuest|journal=Publications of the Astronomical Society of the Pacific |volume=120 |issue=863 |pages=38–88 |doi=10.1086/525059 |last1=Unwin |first1=Stephen C. |last2=Shao |first2=Michael |last3=Tanner |first3=Angelle M. |last4=Allen |first4=Ronald J. |last5=Beichman |first5=Charles A. |last6=Boboltz |first6=David |last7=Catanzarite |first7=Joseph H. |last8=Chaboyer |first8=Brian C. |last9=Ciardi |first9=David R.|last10= Edberg|first10= Stephen J.|last11= Fey|first11= Alan L.|last12= Fischer|first12= Debra A.|last13= Gelino|first13= Christopher R.|last14= Gould|first14= Andrew P.|last15= Grillmair|first15= Carl|last16= Henry|first16= Todd J.|last17= Johnston|first17= Kathryn V.|last18= Johnston|first18= Kenneth J.|last19= Jones|first19= Dayton L.|last20= Kulkarni|first20= Shrinivas R.|last21= Law|first21= Nicholas M.|last22= Majewski|first22= Steven R.|last23= Makarov|first23= Valeri V.|last24= Marcy|first24= Geoffrey W.|last25= Meier|first25= David L.|last26= Olling|first26= Rob P.|last27= Pan|first27= Xiaopei|last28= Patterson|first28= Richard J.|last29= Pitesky|first29= Jo Eliza|last30= Quirrenbach|first30= Andreas|bibcode = 2008PASP..120...38U |arxiv = 0708.3953 |s2cid= 10797266|display-authors= 8}}</ref> tunes SIM Lite's mass sensitivity at each star to a desired level in the habitable planet search.  The value of η<sub>Earth</sub> (Eta_Earth), the fraction of stars carrying Earth-analog planets, will be estimated by the [[Kepler Mission]] some time before SIM Lite launches. One strategy for a habitable planet search is to do a 'deeper' search (i.e. to lower mass sensitivity in the habitable zone) of a smaller number of targets if Earth analogs are common. A 'shallower' search of a larger number of targets could have been done if Earth analogs are rarer. For example, assuming that 40% of mission time is allocated for the planet search, SIM Lite could have surveyed:

* 65 stars for planets down to one Earth mass, in scaled 1 AU orbits, OR
* 149 stars for planets down to two Earth masses, in scaled 1 AU orbits, OR
* 239 stars for planets down to three Earth masses, in scaled 1 AU orbits.

Aside from searching for Earth-sized planets SIM Lite was scheduled to perform what has been dubbed the "Broad Survey". The Broad Survey would have looked at approximately 1,500&nbsp;stars to help determine the abundance of [[Neptune]]-mass and larger planets around all star-types in Earth's sector of the [[Milky Way]].<ref name=davidson/>

[[Image:Earthlike planet-browse.jpg|thumb|left|SIM Lite would have been able to detect Earth-sized planets, such as in this artist's rendering.]]
A third part of the planet finding mission was the search for [[Jupiter]]-mass planets around young stars. The survey would have helped scientists understand more about solar system formation, including the occurrence of [[hot Jupiters]].<ref name=davidson2>Davidson, John et al., Ed., ., ''[http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/simBook2009/ SIM Lite Astrometric Observatory]  {{webarchive|url=https://web.archive.org/web/20100409140747/http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/simBook2009/ |date=9 April 2010 }}'', [http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/SIMLiteBook/Chapter-2-LR.pdf Chapter 2] {{webarchive|url=https://web.archive.org/web/20090827042502/http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/SIMLiteBook/Chapter-2-LR.pdf |date=27 August 2009 }}, Jet Propulsion Laboratory 400–1360, 2009.  Retrieved 8 March 2010.</ref> This portion of the planet hunt was designed to study systems with one or more Jupiter mass planets before the system has reached long term equilibrium.<ref name=davidson2/> Planet hunting techniques using a star's radial velocity cannot measure the regular, tiny to-and-fro wobble motions induced by planets against the strong atmospheric activity of a youthful star. It is through the techniques pioneered by [[Albert A. Michelson]] that the SIM would have been able to execute its three primary planet-finding missions.

The mission's planet finding component was set up to serve as an important complement to the future missions designed to image and measure terrestrial and other exoplanets. SIM Lite was to perform an important task that these missions will not be capable of: determining planet masses.<ref name=davidson3>Davidson, John et al., Ed., ''[http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/simBook2009/ SIM Lite Astrometric Observatory] {{webarchive|url=https://web.archive.org/web/20100409140747/http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/simBook2009/ |date=9 April 2010 }}'', [http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/SIMLiteBook/Chapter-3-LR.pdf Chapter 3] {{webarchive|url=https://web.archive.org/web/20090827042120/http://planetquest.jpl.nasa.gov/SIM/keyPubPapers/SIMLiteBook/Chapter-3-LR.pdf |date=27 August 2009 }}, Jet Propulsion Laboratory 400–1360, 2009.  Retrieved 8 March 2010.</ref> Another task that the SIM was envisioned to perform for the future missions will include providing the orbital characteristics of the planets.<ref name=davidson3 /><ref name=tanner>{{cite journal |bibcode=2005AAS...206.1404C |title=Space Interferometry Mission (SIM) PlanetQuest's Discovery Space and Potential Synergy with Terrestrial Planet Finder (TPF): I. Detection of Terrestrial Planets in the Habitable Zone |last1=Catanzarite |first1=J. |last2=Tanner |first2=A. |last3=Shao |first3=M. |volume=206 |date=2005 |pages=453 |journal=American Astronomical Society Meeting 206}}</ref> With this knowledge other missions can estimate the optimal times and projected star–planet separation angles for them to observe the terrestrial (and other) planets SIM has detected.