March launch for Kepler likely

NASA's Kepler space telescope, a spacecraft designed to hunt for earth-like planets, seems ready for an early March launch. Ball Aerospace & Technologies Corp, the Colorado-based NASA contractor responsible for developing the Kepler flight system and supporting mission operations, has completed the spacecraft's final pre-ship checkout and delivered the spacecraft to Cape Canaveral Air Force Station, for a March 5 lift-off on a Delta 2 booster.

Kepler initially will look at 140,000 stars, with project scientists planning to cut down the field of study to 100,000 stars. Building the NASA Discovery-class Kepler meant harnessing three key capabilities: pointing accuracy, a very large field of view, and low-noise electronics, to maximize the ability to read data from the sensitive detection system.

The timing is right because of the increasing number of extra-solar planets detected in recent years, most of which have been at least the size of Jupiter. Over its three-and-a-half-year mission, Kepler will seek planets 30 to 600 times smaller than Jupiter.

Using a 0.95-metre diameter telescope and an array of 42 charge-coupled devices - the light-sensitive microchips at the heart of the most common digital cameras - Kepler will measure the change in brightness that occurs when a planet transits across the face of its parent star. From that light fluctuation in starlight and time between transits, scientists can determine the size of the planet, the size of the planet's orbit, and even the planet's temperature.

Following launch, Kepler will be nudged into an Earth-trailing heliocentric orbit with a period of 372.5 days. Once positioned, the spacecraft will roll every 30 days to align a fixed high-gain antenna to download that month's gathered readings to NASA's Deep Space Network. Kepler will also carry out a 90-degree roll every 90 days to keep its solar panels always pointed at the sun.

Kepler data is to be relayed to the Data Management Center at the Space Telescope Science Institute in Baltimore, with science data analysis carried out by the NASA Ames Research Center at Moffett Field, California.