Countdown to Kepler & Terra Nova

The Kepler field of view,
straddling the Summer
Triangle (Altair, Vega, Deneb). On March 6th, at 3:48 UTC, a Delta II launch vehicle will rise off the ground at Cape Canaveral's pad 17B, riding a fountain of fire being belched from its RS-27A main engine and 6 GEM-40 solids strapped to its sides like oversized fireworks. Three additional GEM-40 solid rockets get an air start about 2 minutes into flight, and burns of the Delta K second stage and Star 48B third stage will loft the Kepler spacecraft into an orbit around the sun, drifting away from the Earth at slow rate over the following years. After the roaring earthquake-in-a-thunderstorm ride to that orbit, Kepler will settle into the deep interplanetary quiet - an ever waking, watchful sentinel, on the lookout.

During its long stare, Kepler will seek - and find - planets like Earth: the size of Earth, orbiting stars similar to our Sun, separated from their host stars at distances similar to the Earth-Sun system. Places where liquid water are thought to be likely, where life can flourish. Terra Nova.

Kepler will do so by looking with its large, unblinking eye, at a huge, heavenly (literally) host of stars - initially, about 200 thousand - taking a digital picture and measuring the brightness of each of those stars once every few minutes. The exact same field of stars, for 4 long years (and even longer if a mission extension comes to pass). If one of those stars happens to be Sun-like, if it happens to have an Earth-like planet, if that planet happens to be in a Earth-like orbit (about 93 million miles from its host star), if that orbit happens to pass between us and that star, and if Kepler is looking during the transit event, then a detection might occur. Stare long enough, the planet's orbit will swing it around for a second transit, establishing the duration of the orbit - and then later, a third: confirmation. A lot of if's - and the mission design attempt to solve that: look at a lot of stars, with a regular rate, for a very long time - four years or more, in fact. Each one of the "if's" I mentioned has a small likelihood of success associated with it, but if you beat enough targets, for long enough, against those small probabilities, one can still come up with non-zero discovery rates.

Assuming the rocket doesn't blow up on launch (yet another 'if' - but the Delta II's are about as resoundingly reliable as they come), and if the satellite functions properly, what is the expected haul of planets? This is difficult to say, actually - astronomers don't have much information on how common Earth-like planets are - this is a major motivation for the mission. But, if current models are true (they are, every blue moon), the expectation is that roughly 50 Earth-like objects will be found, in addition to a large number of bigger objects (such as Neptune-sized objects).

Currently there's a similar smaller scale mission, CoRoT, flown by the French space agency CNES, which in turn was predated by an even smaller scale mission, MOST, flown by the Canadian Space Agency. CoRoT just celebrated its 2nd year anniversary, and MOST has been orbiting since mid-2003. Both CoRoT and MOST can detect large-ish planets (giant gas bags like Neptune and Jupiter) - particularly if the host star is smaller than our sun - but Kepler's scope (roughly a factor of 10 larger than CoRoT) allowed it to be designed specficially for the goal of finding distinctly Earth-like planets. It's an exciting prospect - one more step on the Copernican Revolution started over 400 years ago, one that will not only expand the frontiers of our scientific knowledge, but one that will distinctly impact humanity's sense of its place in the universe.

* :)