NASA Strategic Plan 2000
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The scientific goal of the Kepler Mission, to explore the structure and diversity of planetary systems, is well focused and responsive to many prominent strategic issues:

• It provides the answer to fundamental question #2 in NASA's Strategic Plan, 2000
• It Contributes to all NASA Office of Space Science Themes
• It addresses the questions on formation and evolution of planets posed in the National Research Council 2001 decadal survey:
• It responses to the NRC decadal survey's call for searches for terrestrial planets before the start of TPF
• It provides exciting scientific results of great visceral interest to the general public about exploration.

This mission follows NASA's well-established history of exploration, that is, to forge into the unknown by first conducting a survey as the basis for the design of future missions. This is the path followed in both solar-system exploration and in astrophysics. Kepler is the scientific pathfinder for TPF and a key element in NASA's Origins program.

By performing an unbiased search of the extended solar neighbor, and with a sensitivity to detect Earth-size planets in the habitable zone of solar-like stars, Kepler is able to answer the question about Earth-like planets -- before the decade is out !

Kepler provides a wealth of data to address many topics in Space Science. The data set is unprecedented in its combination of photometric precision, continuity and duration. The OSS themes and topics supported include:

• Astronomical search for Origins and Planetary systems
  Search for habitable planets:
  frequency, size, orbit, properties of parent star
• Structure and evolution of the Universe
  Stellar evolution:
  p-mode oscillations, rotation rates, spot cycles
  cataclysmic variables, eclipsing binaries,
  Active galactic nuclei variability
• Solar-system-exploration
  Comparing of our solar system to others
• Sun-Earth connection
  Frequency of Maunder minimums (the mini-Ice Age),
  Characteristics of other "solar-like" stars
• Education and Public outreach
  Kepler scientific goals have great public appeal

Kepler addresses the questions on formation and evolution of planets posed in the National Research Council 2001 decadal survey: The following are excerpts from the NRC report

Astronomy and Astrophysics in the New Millennium
published in 2001 by the National Academy Press.

Regarding basic questions the NRC report states:

"The first step is to carry out a census of extrasolar planetary systems in order to answer the following questions:

• What fraction of stars have planetary systems?
• How many planets are there in a typical system, and
• what are their masses and distances from the central star?
• How do these characteristics depend on the mass of the star, its age and whether it has a binary companion?" (p.55)

Regarding methods to address these questions the NRC report states:

• "Space-based photometry is sufficiently precise that it could extend the census down to planets with masses as low as those of the terrestrial planets." (p. 56)
  "The planetary census, together with new observations of protoplanetary disks, will provide the data needed to understand planet formation." (p. 56)

The NRC report Astronomy and Astrophysics in the New Millennium calls for building of the Terrestrial Planet Finder only after demonstrating that Earth-size planets are common. Quoting from the report about the TPF:

• "The committee's recommendation of this mission [TPF] is predicated on the assumptions that TPF will revolutionize major areas of planetary and non-planetary science, and that prior to the start of TPF, ground- and space-based searches will confirm the expectation that terrestrial planets are common around solar-type stars." (pp. 12 and 39)
• "In addition, to ensure that TPF reaches its full scientific potential, it is important to determine prior to the start of the mission that it is likely that there will be an adequate number of Earth-sized planets for TPF to study." (p. 112)

The Kepler Mission does determine if terrestrial planets are common as well as, characterizes these planetary systems and determines their distribution. Quoting from Philip and Phylis Morrison (2000) regarding the Kepler Mission: "Seining a whole sea of stars for the telltale transit dimming pattern looks like the easiest scheme so far for finding Earth-like planets".