The Kepler space telescope is a large, international scientific project launched in 2009 that uses a spacecraft to observe and study planets orbiting other stars. The telescope is named after the German astronomer Johannes Kepler, who discovered the laws of planetary motion.
Kepler is designed to survey our region of the Milky Way galaxy to discover hundreds of Earth-size planets and determine how many of the billions of stars in our galaxy have such planets. This will help us better understand our place in the universe and answer one of humanity’s most fundamental questions: Is there other life out there?
Launched on March 7, 2009, from Cape Canaveral Air Force Station in Florida, USA, aboard a Delta II rocket, Kepler began its mission by observing more than 150,000 main sequence stars in a fixed field of view. In 2013, after completing its original mission objectives, Kepler was repurposed as part of K2 – an extended mission that continues Kepler’s search for exoplanets while also studying star clusters, active galaxies, supernovae and more.
Kepler is currently operating on its 18th campaign as part of K2. As data from each new campaign becomes available (usually every 3 months), it is made public through the Mikulski Archive for Space Telescopes (MAST). Researchers around the world then comb through this data to look for telltale signs of transiting exoplanets. So far, Kepler has confirmed 2335 planets* – with many more discoveries yet to come!
*As of October 30th 2018
The following description gives an overview about what kind of objects can be observed with the specific instrumentation on board:\
textbf{Overview:} The emph{Kepler} space telescope was launched on March 7$^{th}$, 2009 from Cape Canaveral Air Force Station in Florida atop a Delta II rocket cite{kep1}. The primary goal for emph{Kepler’s} four year mission was to survey a large sample size ($>$100 thousand) main sequence stars within our own Milky Way galaxy in order locate any extrasolar planets which might cross (or “transit”) in front their parent star(s) as seen from Earth cite{kep1}. These transits cause periodic dips in stellar brightness which are very difficult detect if only a few transits occur over long time periods or if multiple planet candidates orbit one star since they may blend into each other making it impossible resolve them individually cite{kep4}. However thanks to emph{Kepler’s} high photometric precision (20 ppm per 6 hours integration; $sim$85 $mu$mag/hr cadence), short observational baseline ($sim$3.5 years), and large field-of-view ($115^{circ} times 115^{circ})$, it became possible not only detect but also characterize thousands extrasolar planetary systems via their transit light curves thus providing valuable insights about these distant worlds which would otherwise remain hidden from viewfootnote{url{https://exoplanetarchive.ipac.caltech.edu/}} . \
In addition to hunting for extrasolar planets using the transit method described above where at least one planet must pass directly between us and its host star so we can measure periodic variations stellar brightness caused by successive planetary transits across stellar disk; another way emph{Kepler} searched for new worlds was by looking asteroseismology targets – i.e., bright nearby Sun-like stars whose interior oscillations create tiny ripples brightness which manifest themselves as regular periodic changes flux received here Earthfootnote{url {http://www2kpcacaltechedu/~browning/seismo_starshtm}} . By measuring these oscillations extremely high accuracy it possible obtain direct estimates fundamental parameters such mass radius age without need resort model dependent techniques like those used infer properties eclipsing binaries or transiting giant planets around much fainter host stars since individual seismic modes carry unique information about different layers deep inside target star allowing us probe down all way surface even when said object too faint resolved directly imaging techniques like lucky imaging speckle interferometry adaptive optics etcetera cite { brown11}.\
Furthermore due fact that majority small rocky terrestrial type worlds lack detectable companion gas giants required produce detectable radial velocity variations measured Doppler spectroscopy; means finding truly habitable zone (HZ) terrestrial exoplanets requires sensitive enough monitor orbits long enough duration catch least several full orbits phase space coverage sufficient constrain eccentricity well below $e=0 1$. This combination factors generally precludes detection HZ rocky worlds traditional ground based surveys though ongoing next generation RV projects such CARMENES ESPRESSO HARPS3 GIANO IRD will likely change situation future once they achieve full operational status later this decade provided receive adequate financial support continue operations beyond initial 5–10 year commitment timescale currently envisioned most cases however given significant investment costs building running state art RV telescopes networks necessary maintain continuous monitoring needed catch complete set orbital phases HZ rocky world requires leaving job up space based facilities like TESS Transiting Exoplanet Survey Satellite due launch soon 2018 NASA Webb Telescope due launch sometime 2021 assuming doesn’t experience any further delays construction budget etcetera both which should ideally complement each finding plenty interesting things look during their planned two three year primary missions respectively not mention numerous proposed long term extension missions being studied various stages planning process right now including but limited JWST+TESS+Webb combined science team led Dr Jennifer Wiseman Senior Project Scientist Hubble Space Telescope program Science Mission Directorate NASA Headquarters Washington D C United States America recently submitted report decadal survey committee outlining potential benefits conducting said joint observations over period 2025–2035 provided funding agency agrees cover additional cost conducting said observations course next few years remains seen whether recommendation made decadal survey panel accepted given current political climate within U S government towards science research general though recent developments White House suggest optimists may end having fight hand after all again time will tell . \