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lunes, 26 de septiembre de 2011

ASTRONOMY: Kepler Mission Description

Hi My Friends: A VUELO DE UN QUINDE EL BLOG., The Kepler instrument is a specially designed 0.95-meter diameter telescope called a photometer or light meter. It has a very large field of view for an astronomical telescope 105 square degrees, which is comparable to the area of your hand held at arm's length. The fields of view of most telescopes are less than one square degree. Kepler needs the large field of view in order to observe the large number of stars. It stares at the same star field for the entire mission and continuously and simultaneously monitors the brightnesses of more than 100,000 stars for at least 3.5 years, the initial length of the mission, which can be extended.

Kepler Spacecraft and Photometer(Launched on March 6, 2009)


Kepler Scientific Objectives

The scientific objective of the Kepler Mission is to explore the structure and diversity of planetary systems. This is achieved by surveying a large sample of stars to:
1.- Determine the percentage of terrestrial and larger planets that are in or near the habitable zone of a wide variety of stars
2.- Determine the distribution of sizes and shapes of the orbits of these planets
3.- Estimate how many planets there are in multiple-star systems
4.- Determine the variety of orbit sizes and planet reflectivities, sizes, masses and densities of short-period giant planets
5.- Identify additional members of each discovered planetary system using other techniques
6.- Determine the properties of those stars that harbor planetary systems.

Image above: Kepler's targeted star field. Credit: Carter Roberts of the Eastbay Astronomical Society


Kepler Mission Star Field
An image by Carter Roberts of the Eastbay Astronomical Society in Oakland, CA, showing the Milky Way region of the sky where the Kepler spacecraft/photometer will be pointing. Each rectangle indicates the specific region of the sky covered by each CCD element of the Kepler photometer. There are a total of 42 CCD elements in pairs, each pair comprising a square. Credit: Carter Roberts

Kepler Mission Description
Kepler, a NASA Strategic mission launched into an Earth-trailing heliocentric orbit on March 6, 2009, is designed to stare at a 105 square degree region of the sky in the constellations of Cygnus and Lyra. The mission's goal is to obtain long-term, unfiltered, and precise light curves of up to 100,000 cool stars and search for periodic transits of planets as small as the Earth. A secondary objective of the mission is to study rapid oscillations of the target stars in order to determine their ages, radii, and metallic chemical compositions of planet-hosting stars. The Kepler Science page and Science Goals pages lay out the scientific objectives in some detail.
The science operations phase of the mission began on May 12, 2009. Since then Kepler has monitored the same sky field almost continuously. The principal exception is for monthly data downlinks during which the spacecraft must turn away from the monitored field, reorient toward the Earth for the downlink, and return to the field. The spacecraft also "rolls" every three months to allow for continous illumination of Kepler's solar arrays. A table of scheduled quarterly rolls, each lasting about 1 day, is given on the MAST/Kepler FAQ page (see FAQ tab in left "gutter"). The fields of view of 42 CCDs covers a four-way symmetrical pattern on the sky such that the same stars remain on the detectors during the mission. Although the Kepler field covers a large sky area containing millions of stars, data from small regions around only 150,000 targets are recorded and stored onboard the spacecraft. The default integration time is about 30 minutes, although a small number of asteroseismology and other targets of interest are recorded with integration times of about 1 minute.
The mission has a nominal lifetime of three and one half years to pursue its core science objectives. These objectives will be carried out by Science Principal Investigator William Borucki of NASA's Ames Research Center, the Kepler Science Team, the Kepler Participating Scientists, and the Kepler Asteroseismology Science Consortium. In addition, a limited Guest Observer (GO) program, dedicated to general (non-exoplanetary) astrophysics has been established. Proposal solicitations will be made on an annual basis, resources permitting, by NASA Headquarters. The GO program is administered from NASA's Ames Research Center. Information of interest to potential GO proposers can be found at the GO program website and in NASA's omnibus annual announcement Research Opportunities in Space and Earth Sciences 2010 NASA ROSES.
A map of where Kepler's Field of View in the sky was obtained from the Project and is shown below. Clicking on this image will bring up a magnified view. Users can reconnoiter the Kepler field in detail by going to the FFI display page.
Investigators interested in whether targets included in the MAST/Kepler ("KIC") database lie on any of the 42 Kepler detector fields should first consult the Kepler Target Search form. Users are also emphatically advised not to use solely color-derived quantities like Teff, logg, etc. to select their targets for proposals.
As the mission proceeds, the Project will periodically drop stars as exoplanetary search candidates. As it does so, MAST will provide access to lists of targets and/or data released as notifications in the Dropped Target and Published Target tabs under the Search and Retrieval item on the left banner of this page and in the Public Light Curves link in the Quick Links section above. As data become nonproprietary, the restrictions against accessing them, which are denoted by the "yellow band" on the Retrieval page, will disappear. In addition to the Dropped and Target lists, Kepler light curves and associated ground-based follow up data have been also placed on MAST's Kepler High Level Science Products site.
Image above: Kepler's targeted star field graphic. Credit: NASA

Target Field of View :
Since transits only last a fraction of a day, all the stars must be monitored continuously, that is, their brightnesses must be measured at least once every few hours. The ability to continuously view the stars being monitored dictates that the field of view (FOV) must never be blocked at any time during the year. Therefore, to avoid the Sun the FOV must be out of the ecliptic plane. The secondary requirement is that the FOV have the largest possible number of stars. This leads to the selection of a region in the Cygnus and Lyra constellations of our Galaxy as shown.

Guillermo Gonzalo Sánchez Achutegui
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