A couple more interesting things about the just-launched
Unlike the Hubble Space Telescope, which orbits Earth, Kepler has been placed in what's called an "Earth trailing" orbit around the sun. A little wider and slower than our own orbit, the spacecraft will take 371 days to complete one circuit. Each day Kepler falls a little farther behind Earth—eventually the gap will open to tens of millions of miles. This unusual orbit, designed by Johnny Kwok of the Jet Propulsion Laboratory and used for the first time with the Spitzer infrared space telescope launched in 2003, has advantages for astronomical telescopes. One is that Earth doesn't block their view of the sky. The spacecraft doesn't need periodic boosts to maintain its altitude above Earth. And best of all, it's a very fuel-efficient orbit, requiring less energy (smaller rocket, lower cost) to reach than the L2 Lagrange point that originally was to have been Kepler's destination. Expect these Earth-trailing orbits to become a popular choice for future astronomy missions.